Patent Publication Number: US-2007100242-A1

Title: Electronic blood pressure monitor with which evaluation quantity related to cardiovascular risks can be calculated

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to an electronic blood pressure monitor, and in particular, to an electronic blood pressure monitor with which an evaluation quantity related to cardiovascular risks can be calculated.  
      2. Description of the Background Art  
      The blood pressure is one of indices for analyzing the circulatory diseases. Performing risk analysis based on the blood pressure is effective for preventing cardiovascular diseases such as cerebral apoplexy, cardiac failure, and myocardial infarction. Especially the morning hypertension, an increased blood pressure in the early morning, has relation with cardiac diseases and cerebral apoplexy. Among the morning hypertension, the symptom that the blood pressure rapidly increases during the time after one to one and half hours from getting up, called “morning surge”, has been found to have a cause-effect relationship with the cerebral apoplexy. This is disclosed in detail in Kazuomi Kario, “Risk of Morning Hypertension and Cerebrovascular Disease”, Journal of Blood Pressure, November issue, Sentan Igaku-sha, Nov. 1, 2002, vol. 9, no. 11, pp. 94-97. Accordingly, it is useful to recognize the correlation between the time (living habit) and the change in blood pressure for risk analysis of the cardiovascular diseases.  
      It is known that the blood pressure greatly varies depending on numerous physiological and environmental factors. In order to eliminate such variation, it is recommended to measure the blood pressure for a plurality of times and to determine using the average value of the measurement values. Detailed description thereof is provided in “Guidelines for the Management of Hypertension”, the Japanese Society of Hypertension, Dec. 20, 2004, pp.7-8, and “Number of Measurements”, the American Heart Association, “Hypertension”, January 2005, vol. 45, pp.151-152.  
      Conventionally, various attempts have been made to manage the trend of blood pressure. For example, Japanese Patent Laying-Open No. 04-221528 (U.S. Pat. No. 3,033,849) proposes a blood pressure monitor, with which blood pressure values, identification data, and the measurement date are recorded, and the blood pressure values provided with the identical identification data are selectively displayed. Also, the trend graph corresponding to the measurement situation is displayed.  
      On the other hand, according to Japanese Patent Laying-Open No. 04-221528, the blood pressure values are selected in accordance with the measurement time or the measurement situation that is input at the time of measurement or record. Therefore, calculation of a highly reliable evaluation quantity is not ensured, even if such technique is used.  
     SUMMARY OF THE INVENTION  
      The present invention has been made to solve the above-described problem, and an object thereof is to provide an electronic blood pressure monitor with which a highly reliable evaluation quantity can be calculated.  
      In order to achieve the above-described object, an electronic blood pressure monitor according to one aspect of the present invention includes: a measuring unit measuring a blood pressure of a subject; a data discriminating unit discriminating whether measured blood pressure data is calculation data for calculating an evaluation quantity; a storing unit storing the measured blood pressure data in association with at least one of a plurality of measurement conditions; a first retrieving unit retrieving a plurality of pieces of blood pressure data measured in a prescribed period from the blood pressure data stored in the storing unit; and a first determining unit determining whether at least a plurality of prescribed number of pieces of blood pressure data corresponding to each of the plurality of measurement conditions are present in the plurality of pieces of blood pressure data retrieved by the first retrieving unit. The first determining unit performs the determination for the blood pressure data discriminated as the calculation data by the data discriminating unit. The electronic blood pressure monitor further includes: a first average value calculating unit calculating, when the first determining unit determines that at least the plurality of prescribed number of pieces of blood pressure data are present, a first average value of a blood pressure data group that includes the at least the plurality of prescribed number of pieces of blood pressure data, for each of the measurement conditions; a first evaluation quantity calculating unit calculating a first correlated evaluation quantity based on correlation of the first average values respectively calculated for the measurement conditions; and a display unit displaying a calculation result of the first evaluation quantity calculating unit.  
      A “measurement condition” is information indicative of a physical state of the subject at the time of blood pressure measurement, and in particular, information indicative of a specific state that can be used for calculating the evaluation quantity.  
      Preferably, the plurality of measurement conditions include an after-waking-up time slot and a before-sleeping time slot. The blood pressure monitor further includes: a time measuring unit measuring a time point; a time point specifying unit specifying a sleep time point based on an instruction from the subject; and a condition determining unit determining to which of the plurality of measurement conditions a measurement condition at the blood pressure measurement applies, based on time point data output from the time measuring unit. The data discriminating unit includes a time determining unit determining whether a prescribed time has elapsed from the sleep time point specified by the time point specifying unit, based on the time point data output from the time measuring unit, when the condition determining unit determines that the measurement condition is the after-waking-up time slot. The data discriminating unit discriminates the measured blood pressure data as the calculation data, when the time determining unit determines that the prescribed time has elapsed.  
      Alternatively, it is desirable that the plurality of measurement conditions include an after-waking-up time slot and a before-sleeping time slot, and the blood pressure monitor further includes: a time measuring unit measuring a time point; and a condition determining unit determining to which of the plurality of measurement conditions a measurement condition at the blood pressure measurement applies, based on time point data output from the time measuring unit. The data discriminating unit includes a time determining unit determining whether a prescribed time has elapsed from a time point as measured in the before-sleeping time slot in the prescribed period, based on the time point data output from the time measuring unit, when the condition determining unit determines that the measurement condition is the after-waking-up time slot. The data discriminating unit discriminates the measured blood pressure data as the calculation data, when the time determining unit determines that the prescribed time has elapsed.  
      Preferably, the blood pressure data discriminated as the calculation data by the data discriminating unit is stored in the storing unit in association with the measurement conditions.  
      Preferably, based on a discrimination result of the data discriminating unit, identification information indicating whether the blood pressure data is the calculation data and the measured blood pressure data are stored in the storing unit in association with the measurement conditions.  
      Preferably, the first determining unit determines whether at least the plurality of prescribed number of pieces of blood pressure data, which correspond to each of the plurality of measurement conditions and in which the identification information indicates that the blood pressure data is the calculation data, are present, in the retrieved plurality of pieces of blood pressure data.  
      Preferably, the prescribed period is a period that is “an evaluation day” including one after-waking-up time slot and one before-sleeping time slot.  
      Preferably, the blood pressure monitor further includes: a second retrieving unit retrieving a plurality of blood pressure data measured in a specific period that is longer than the prescribed period, from the blood pressure data stored in the storing unit; a second determining unit determining whether at least the plurality of prescribed number of pieces of blood pressure data corresponding to each of the plurality of measurement conditions for each the prescribed period are present in the plurality of pieces of blood pressure data retrieved by the second retrieving unit; a second average value calculating unit excluding blood pressure data measured in a period determined by the second determining unit that at least the plurality of prescribed number of pieces of blood pressure data are not present, to calculate a second average value for each of a plurality of blood pressure data groups, for each of the measurement conditions; and a second evaluation quantity calculating unit calculating a second correlated evaluation quantity based on correlation of the second average values for each of the measurement conditions.  
      Preferably, the specific period is one of a week, a month, a season, and a year.  
      In order to achieve the above-described object, a blood pressure monitor according to another aspect of the present invention includes: a measuring unit measuring a blood pressure of a subject; a data discriminating unit discriminating whether measured blood pressure data is calculation data for calculating an evaluation quantity; a storing unit storing the measured blood pressure data in association with at least one measurement condition; a first retrieving unit retrieving a plurality of pieces of blood pressure data measured in a prescribed period from the blood pressure data stored in the storing unit; and a first determining unit determining whether at least a plurality of prescribed number of pieces of blood pressure data corresponding to a prescribed measurement condition are present in the plurality of pieces of blood pressure data retrieved by the first retrieving unit. The first determining unit performs the determination for the blood pressure data discriminated as the calculation data by the data discriminating unit. The electronic blood pressure monitor further includes: a first average value calculating unit calculating, when the first determining unit determines that at least the plurality of prescribed number of pieces of blood pressure data are present, a first average value of a blood pressure data group including the at least the plurality of prescribed number of pieces of blood pressure data, for the prescribed measurement condition; a first evaluation quantity calculating unit calculating a first evaluation quantity based on the first average value; and a display unit displaying a calculation result of the first evaluation quantity calculating unit.  
      Preferably, the prescribed measurement condition corresponds to an after-waking-up time slot. The blood pressure monitor further includes: a time measuring unit measuring time point; a time point specifying unit specifying a sleep time point based on an instruction from the subject; and a condition determining unit determining whether a measurement condition at the blood pressure measurement applies to the at least one measurement condition, based on time point data output from the time measuring unit. The data discriminating unit includes a time determining unit determining whether a prescribed time has elapsed from the sleep time point specified by the time point specifying unit, based on the time point data output from the time measuring unit, when the condition determining unit determines that the measurement condition is the prescribed measurement condition. The data discriminating unit discriminates the measured blood pressure data as the calculation data, when the time determining unit determines that the prescribed time has elapsed.  
      Alternatively, it is desirable that the prescribed measurement condition corresponds to an after-waking-up time slot. The blood pressure monitor further includes: a time measuring unit measuring a time point; and a condition determining unit determining whether a measurement condition at the blood pressure measurement applies to the at least one measurement condition, based on time point data output from the time measuring unit. The data discriminating unit includes a time determining unit determining whether a prescribed time has elapsed from a time point as measured in a before-sleeping time slot in the prescribed period, based on the time point data output from the time measuring unit, when the condition determining unit determines that the measurement condition is the prescribed measurement condition. The data discriminating unit discriminates the measured blood pressure data as the calculation data, when the time determining unit determines that the prescribed time has elapsed.  
      Preferably, the blood pressure data discriminated as the calculation data by the data discriminating unit is stored in the storing unit in association with the prescribed measurement condition.  
      Preferably, based on a discrimination result of the data discriminating unit, identification information indicating whether the blood pressure data is the calculation data and the measured blood pressure data are stored in the storing unit in association with the prescribed measurement condition.  
      Preferably, the first determining unit determines whether at least the plurality of prescribed number of pieces of blood pressure data, which correspond to the prescribed measurement condition and in which the identification information indicates that the blood pressure data is the calculation data, are present, in the retrieved plurality of pieces of blood pressure data.  
      Preferably, the prescribed period is a period that is an evaluation day including one the after-waking-up time slot.  
      Preferably, the blood pressure monitor further includes: a second retrieving unit retrieving a plurality of blood pressure data measured in a specific period that is longer than the prescribed period, from the blood pressure data stored in the storing unit; a second determining unit determining whether at least the plurality of prescribed number of pieces of blood pressure data corresponding to the prescribed measurement condition for each the prescribed period are present in the plurality of pieces of blood pressure data retrieved by the second retrieving unit; a second average value calculating unit excluding blood pressure data measured in a period determined by the second determining unit that at least the plurality of prescribed number of pieces of blood pressure data are not present, to calculate a second average value for each of a plurality of blood pressure data groups, for the prescribed measurement condition; and a second evaluation quantity calculating unit calculating a second correlated evaluation quantity based on correlation of the second average values for the prescribed measurement condition.  
      According to the present invention, for each measurement condition, an average value of at least a plurality of prescribed number of pieces of blood pressure data is calculated. Based on the calculated average value, the evaluation quantity is calculated. Thus, variation factors of blood pressure data dependent on psychological tension and the like of the subject at the measurement can be absorbed. Accordingly, a highly reliable evaluation quantity can be calculated.  
      The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an overview of an electronic blood pressure monitor according to first and second embodiments and first and second modifications of the second embodiment of the present invention.  
       FIG. 2  shows the internal configuration of the blood pressure monitor according to the first and second embodiments and the first and second modifications of the second embodiment of the present invention.  
       FIGS. 3A and 3B  show exemplary storage contents of measurement results in a memory according to the first and second embodiments and the second modification of the second embodiment of the present invention.  
       FIG. 4  is a flowchart of a main routine executed by a CPU of the electronic blood pressure monitor of the first embodiment of the present invention.  
       FIG. 5  is a flowchart of a subroutine showing the measurement result storing process according to the first embodiment of the present invention.  
       FIGS. 6A-6C  show exemplary screen display when the subject inputs measurement time information.  
       FIGS. 7A and 7B  show exemplary contents of a time association table.  
       FIG. 8  shows a first exemplary display of risk value calculation results.  
       FIG. 9  shows a second exemplary display of risk value calculation results.  
       FIG. 10  shows a third exemplary display of risk value calculation results.  
       FIG. 11  is a flowchart showing an interrupt process started when a risk switch is manipulated in the first embodiment.  
       FIG. 12  is a flowchart of a main routine executed by the CPU of the electronic blood pressure monitor of the second embodiment.  
       FIG. 13  is a flowchart of a subroutine showing a measurement result storing process in the second embodiment of the present invention.  
       FIGS. 14A and 14B  show exemplary configuration of a memory in the first modification of the second embodiment of the present invention.  
       FIG. 15  is a flowchart showing a measurement result storing process in the first modification of the second embodiment of the present invention.  
       FIG. 16  is a flowchart showing the flow of an interrupt process started when a sleep time switch is manipulated in the second modification of the second embodiment of the present invention.  
       FIG. 17  is a flowchart showing a measurement result storing process in the second modification of the second embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same units and components have the same reference characters allotted, and detailed description thereof will not be repeated.  
     First Embodiment  
       FIG. 1  is an overview of an electronic blood pressure monitor  100  according to first and second embodiments of the present invention. Referring to  FIG. 1 , electronic blood pressure monitor  100  of the present embodiment includes a blood pressure monitor main body  1 , a cuff  2  fitted to a blood pressure measurement site of a subject and pressurized by an air pressure, and an air tube  3  connecting blood pressure monitor main body  1  with cuff  2 .  
      Blood pressure monitor main body  1  includes a display unit  4  provided for allowing the subject to check a displayed content, and a power supply switch  5 , a measurement switch  6 , a memory switch  7 , a risk switch  8 , and a sleep time switch  9 , provided for allowing the subject to externally manipulate. It is noted that sleep time switch  9  may not be provided to blood pressure monitor main body  1  of the first embodiment. Sleep time switch  9  will be described in the second embodiment later.  
      Power supply switch  5  is manipulated for turning ON/OFF the power supply of blood pressure monitor main body  1 . Measurement switch  6  is manipulated for instructing start of blood pressure measurement. Memory switch  7  is manipulated for calling stored measurement blood pressure data (as used herein, “calling blood pressure data” means reading blood pressure data from a memory, described later, and displaying the read blood pressure data). Risk switch  8  is manipulated for instructing calculation of a risk value based on the stored blood pressure data.  
       FIG. 2  shows the internal configuration of blood pressure monitor main body  1 . Referring to  FIG. 2 , blood pressure monitor main body  1  includes a pressure sensor  14  the volume of which changes in accordance with the pressure of an air bag  21  contained in cuff  2  (hereinafter referred to as “the cuff pressure”), an oscillator circuit  15  that outputs a signal having the oscillation frequency according to the volume value of pressure sensor  14 , a pump  16  and a valve  18  for adjusting the level of cuff pressure, a pump driving circuit  17  driving pump  16 , and a valve driving circuit  19  for adjusting opening/closing degree of valve  18 . Blood press monitor main body further includes a CPU (Central Processing Unit)  20  for centrally controlling and monitoring respective units, a display unit  4 , a memory  12  storing various data and programs, a manipulation unit  300 , a timer  13  that performs time-measuring operation and outputs the time data, a buzzer  24  and a power supply unit  25  for supplying power. Air bag  21  is connected to pressure sensor  14 , pump  16  and valve  18  via air tube  3 . CPU  20  converts a signal obtained from oscillator circuit  15  to sense the pressure.  
      CPU  20  performs functions of a blood pressure calculating unit  200 , first and second evaluating units  201  and  202 , first and second retrieving units  203  and  204 , first and second determining units  205  and  206 , first and second averaging units  207  and  208 , a condition determining unit  209 , a time point specifying unit  210 , and data discriminating unit  211  having a time determining unit  212 . The functions of these units of CPU  20  are implemented when CPU  20  reads and executes corresponding programs that are stored in advance in memory  12 .  
      Manipulation unit  300  includes power supply switch  5 , measurement switch  6 , memory switch  7 , risk switch  8 , and sleep time switch  9 , shown in  FIG. 1 .  
      In the above-described configuration, at the time of blood pressure measurement, blood pressure calculating unit  200  of CPU  20  applies a prescribed algorithm to the pressure data sensed based on a signal from oscillator circuit  15  to calculate blood pressure values, that is, a systolic blood pressure, a diastolic blood pressure, and a pulse rate. Conventionally available well-known procedures can be used for such measurement, and thus, detailed description thereof is not provided here. Hereinafter, thus calculated blood pressure values, or the blood pressure values and the pulse rate may also be referred to as “the measurement results”. The measurement results are stored in memory  12  in association with the measurement conditions at the time of blood pressure measurement.  
      In the present embodiment, the measurement conditions are, as described above, the information indicative of a physical state of the subject at the time of blood pressure measurement, and in particular, the information indicative of a specific state that can be used for calculating the evaluation quantity. That is, the measurement conditions may refer to, for example, after waking up, before sleeping, after exercise, before exercise, before meal, after meal and the like. The measurement conditions may correspond to periods (for example, time slots) or to timings (for example, time, date, day of the week, month, year, season and the like).  
      Here, first, calculation of the evaluation quantity will be described.  
      As to Calculation of Evaluation Quantity  
      In the first embodiment and the second embodiment, which will be described later, as the evaluation quantity, for example a cardiovascular risk value is calculated. The cardiovascular risk value is considered to be useful in preventing cardiovascular events such as cerebral apoplexy, cardiac failure, cerebral infarction, cerebral hemorrhage, subarachnoid hemorrhage, transient cerebral ischemic attack, fall, syncope, vertigo, dizziness, myocardial infarction, angina pectoris, asymptomatic cardiac ischemia, arrhythmia, sudden death, dissecting aortic aneurysm, and rupture of aortic aneurysm.  
      As above, it is known that the blood pressure greatly varies by numerous physiological and environmental factors. Specifically, there are the variation due to progress of aging or disease, the variation dependent on time called seasonal variation and circadian variation, the variation dependent on psychological tension or physical activities, the variation synchronized with respiration, and the like. As cardiovascular risk evaluation, among such variations, it is necessary to evaluate (measure) the long-term variations of the variation due to progress of aging or disease and the seasonal variation, and the short-term variation of the circadian variation. On the other hand, if the variation dependent on psychological tension or physical activities or the variation synchronized with respiration (hereinafter, they are referred to as “psychological variations”) is included in the evaluation (measurement values), the evaluation becomes less reliable and accurate risk determination becomes difficult. With a conventional electronic blood pressure monitor, such psychological variations have not been taken into account, and whether data sufficient for eliminating the psychological variations is obtained has been unclear.  
      Accordingly, first evaluating unit  201  of electronic blood pressure monitor  100  of the first embodiment of the present invention calculates an evaluation quantity by the following calculation method.  
      First Calculation Example  
      In the first calculation example, an evaluation quantity is calculated based on the correlation between a first blood pressure data group including at least a plurality of prescribed number of pieces of blood pressure data corresponding to an identical measurement condition among blood pressure data measured in a prescribed period and stored in memory  12 , and a second blood pressure data group including at least a plurality of prescribed number of pieces of blood pressure data corresponding to another measurement condition. For example, first, an intra-group average value of blood pressure data included in the first blood pressure data group and an intra-group average value of blood pressure data included in the second blood pressure data group are calculated by first averaging unit  207 . Then, for example an average value and difference value of the calculated intra-group average values are calculated as the evaluation quantities (the risk values).  
      That is, in the first calculation example, only when at least a plurality of prescribed number of pieces of blood pressure data measured in a prescribed period are present for each of the measurement conditions, an average value of the blood pressure data for each of the measurement conditions is calculated to obtain the evaluation quantity. It is noted that it is only necessary for the blood pressure data corresponding to each of the measurement conditions to be present in a plurality of numbers, and the number may be set differently for each of the measurement conditions.  
      Second Calculation Example  
      In the second calculation example, the evaluation quantity is calculated based on a blood pressure data group corresponding to a prescribed (one) measurement condition among blood pressure data measured in a prescribed period and stored in memory  12 . In this case, first, an intra-group average value of at least a plurality of prescribed number of pieces of blood pressure data included in a blood pressure data group corresponding to a prescribed measurement condition is calculated by first averaging unit  207 . Then, for example based on the calculated intra-group average value and a predetermined threshold value or a predetermined calculation formula, the evaluation quantity (the risk value) is calculated.  
      That is, in the second calculation example, only when at least a plurality of prescribed number of pieces of blood pressure data measured in a prescribed period are present for a prescribed measurement condition, an average value of the blood pressure data for the measurement condition is calculated to obtain the evaluation quantity.  
      Here, “a prescribed period” refers to an evaluation day, that is, the period of the smallest unit for calculating the evaluation quantity. In the first calculation example, the evaluation day includes each of at least two measurement conditions to be the target of evaluation quantity calculation, while in the second calculation example, the evaluation day includes one of at least one measurement condition to be the target of evaluation quantity calculation.  
      In the following, in the first embodiment of the present invention, the description is given assuming that the evaluation quantity related to morning hypertension is calculated in accordance with the first calculation example described above.  
      In this case, condition determining unit  209  of CPU  20  refers to information for specifying a measurement condition, for example, time information, to determine to which of a plurality of predetermined measurement conditions the physical status of the subject at the time of blood pressure measurement applies. In the first embodiment, the plurality of measurement conditions include, for example, two measurement conditions of an after-waking-up time slot and a before-sleeping time slot. The after-waking-up time slot and the before-sleeping time slot may be determined in advance, or may be set by the subject. In the present embodiment, it is assumed that, as information for specifying measurement conditions (the after-waking-up time slot and the before-sleeping time slot) by the subject, time information (hereinafter referred to as “measurement time information”) is input and set. Thus, even when the subject is a shift worker and the like, an accurate evaluation quantity can be calculated.  
      As above, in the present embodiment, the evaluation quantity is calculated based on the blood pressure data measured in the after-waking-up time slot and in the before-sleeping time slot, and therefore the evaluation day is a period including one after-waking-up time slot and one before-sleeping time slot. For example, it may be a period from the start of the before-sleeping time slot until the end of the after-waking-up time slot, or may be a period from the start of the before-sleeping time slot until the start of next before-sleeping time slot. In this case, the before-sleeping time slot of the previous day and the after-waking-up time slot of today constitute the evaluation day as one set. While herein description is given assuming that a period from the start of the before-sleeping time slot until the end of the after-waking-up time slot constitutes the evaluation day, the evaluation day may be constituted by a period from the start of the after-waking-up time slot until the end of the before-sleeping time slot. That is, the after-waking-up time slot of today and the before-sleeping time slot of today may constitute the evaluation day as one set. Also, the before-sleeping time slot of today and the after-waking-up time slot of the next day may constitute the evaluation day as one set. Also, for example when the before-sleeping time slot and the after-waking-up time slot are fixed time slots, the evaluation day may correspond to 24 hours.  
      When the evaluation quantity is calculated by the second calculation example, the evaluation day is a period including a prescribed measurement condition, e.g., the after-waking-up time slot. For example, it may be a period from the start of the after-waking-up time slot until the end thereof, or may be a period from the start of the after-waking-up time slot until the start of next after-waking-up time slot. Also, for example when the before sleeping→after-waking-up time slot is a fixed time slot, the evaluation day may correspond to 24 hours.  
      Next, a specific exemplary content of memory  12  in the first embodiment is shown in  FIGS. 3A and 3B .  
      Referring to  FIG. 3A , to memory  12 , division of measurement conditions, that is, storage areas  26  and  27  for the before-sleeping time slot and the after-waking-up time slot, respectively, are provided in advance. To each of areas  26  and  27 , a measurement result is stored on a record R-by-record R basis. Record R includes measurement time point data T, systolic blood pressure data SBP indicative of systolic blood pressure, diastolic blood pressure data DBP indicative of diastolic blood pressure and pulse rate data PLS indicative of pulse rate.  
      As to measurement time point data T, data of measurement time point (the time point of starting or ending measurement) measured by timer  13  is input to CPU  20 , which is then converted into measurement time point data T (year, month, day, hour, minute, day of the week) and stored in record R.  
      It is noted that such data is only necessary to be stored in each area as associated, and it is not limited to the storing format using record R. Also, areas  26  and  27  may be provided for each evaluation day so that measurement results may be stored in each of the applicable areas as record R. In this case, record R may not include measurement time point data T.  
      Referring to  FIG. 3B , in memory  12 , measurement results and measurement condition information are stored in pairs. In  FIG. 3B , record Ri (i=1, 2, 3, . . . , n) in which measurement results and measurement condition information are associated with each other is stored. In record Ri, measurement time point data Ti, systolic blood pressure data SBPi, diastolic blood pressure data DBPi, pulse rate data PSLi, and measurement condition data C 1  or C 2  are stored. Measurement condition data C 1  and C 2  correspond to measurement condition divisions, that is, the before-sleeping time slot and the after-waking-up time slot, respectively. In this example also, an area may be provided for each evaluation day so that measurement results are stored in the applicable area as record R. In this case also, record R may not include measurement time point data T.  
      In the following description, as shown in  FIG. 3A , it is assumed that blood pressure data is grouped for each measurement condition and stored in each memory area. In the present embodiment, only the measurement results determined to be measured in the before-sleeping time slot or the after-waking-up time slot are stored in memory  12 . However, a memory area may separately provided for storing measurement results measured when the state of the subject at the time of blood pressure measurement is not in the specific state (i.e., not applicable to either measurement condition), that is, measured in a time slot other than the before-sleeping time slot and the after-waking-up time slot. In this case, every time the blood pressure is measured, the measurement results are stored in any of the memory areas in memory  12 . Thus, all the measured blood pressure data can be recorded.  
      Next, a specific evaluation quantity calculation process executed by electronic blood pressure monitor  100  of the first embodiment of the present invention is described.  
      CPU  20  calculates a risk value based on a program of cardiovascular risk value calculation stored in advance in an internal memory or memory  12 . In order to calculate the risk value, first, first averaging unit  207  of CPU  20  performs a process of reading blood pressure data stored in memory  12  and calculating the average of a plurality of prescribed number of pieces of (for example, three) blood pressure data for each of areas  26  and  27  as shown in  FIG. 3A . That is, it calculates, for each blood pressure group, an intra-group average of a blood pressure group including a plurality of pieces of blood pressure data measured under the identical measurement condition. Then, first evaluating unit  201  calculates a risk value using the calculated average blood pressure values of intra-blood pressure data group.  
      The average blood pressure values are calculated using the following equations: 
 
average of SBP measured after waking up=(data of systolic blood pressure measured after waking up SBP1+data of systolic blood pressure measured after waking up SBP2+ . . . +data of systolic blood pressure measured after waking up SBPn)/ n −(where  n= 1, 2, 3, . . . ); 
 
average of DBP measured after waking up=(data of diastolic blood pressure measured after waking up DBP1+data of diastolic blood pressure measured after waking up DBP2+ . . . +data of diastolic blood pressure measured after waking up DBPn)/ n  (where  n= 1, 2, 3, . . . ); 
 
average of SBP measured before sleeping=(data of systolic blood pressure measured before sleeping SBP1+data of systolic blood pressure measured before sleeping SBP2+ . . . +data of systolic blood pressure measured before sleeping SBPn)/ n  (where  n= 1, 2, 3, . . . ); and 
 
average of DBP measured before sleeping=(data of diastolic blood pressure measured before sleeping DBP1+data of diastolic blood pressure measured before sleeping DBP2+ . . . +data of diastolic blood pressure measured before sleeping DBPn)/ n  (where  n= 1, 2, 3), . . . ). 
 
      The average of pulse rate is calculated using the following equations: 
 
average of pulse rate PLS measured after waking up=(data of pulse rate measured after waking up PLS1+data of pulse rate measured after waking up PLS2+ . . . +data of pulse rate measured after waking up PLSn)/ n  (where  n= 1, 2, 3, . . . ); and 
 
average of pulse rate PLS measured before sleeping=(data of pulse rate measured before sleeping PLS1+data of pulse rate measured before sleeping PLS2+ . . . +data of pulse rate measured before sleeping PLSn)/ n  (where  n =1, 2, 3, . . . ). 
 
      For calculating the risk values, the average value of blood pressure values respectively measured in the before-sleeping time slot and in the after-waking-up time slot (ME average value) and the difference between them (ME difference), which are calculated by the following equations, are used. 
 
ME difference=average of SBP measured after waking up−average of SBP measured before sleeping 
 
ME average=(average of SBP measured after waking up+average of SBP measured before sleeping)/2 
 
      With electronic blood pressure monitor  100  according to the present invention, blood pressure data groups respectively including a plurality of blood pressure values measured in the before-sleeping time slot and in the after-waking-up time slot (data to be included in before sleeping area  26  and after waking up area  27 ) are obtained, and the average values are calculated respectively for the blood pressure data groups. Thereafter, two cardiovascular disease risk values, namely, the average value (ME average value) and difference (ME difference) between the groups, are calculated and presented (displayed) as the result.  
      It is noted that, not only presenting ME average value and ME difference as above, but also differences between ME average value and a predetermined threshold value (for example, 135 mmHg) and between ME difference and a predetermined threshold value (for example, 20 mmHg) may further be calculated, so that the calculated respective differences can be presented (displayed) as the risk values. Also, the risk determination result may be presented (displayed) in a prescribed displaying manner based on the calculated respective difference values. Such display of the risk determination result allows the subject to easily recognize whether the calculated risk values are higher or lower than reference values. For example, when ME difference &gt;20 mmHg and ME average 135 mmHg, it is determined as morning hypertension. It may also be possible to determine as morning hypertension when ME difference &gt;20 mmHg, as shown in Japanese Patent Laying-Open No. 04-221528. The reference values for the determination are stored in the internal memory (not shown) of CPU  20  in advance.  
      First evaluating unit  201  of CPU  20  may calculate, for example, a difference between the calculated intra-group average values to display the magnitude relation between the two average values as a risk determination result.  
      When the evaluation quantity is calculated according to the second calculation example described above, the evaluation value, that is, the risk value is calculated as follows. CPU  20  calculates the risk value based on a program of cardiovascular risk value calculation stored in advance in an internal memory or memory  12 , as described above. In order to calculate the risk value, first, first averaging unit  207  of CPU  20  performs a process of reading blood pressure data stored in memory  12  and calculating the average of a plurality of prescribed number of pieces of (for example, three) blood pressure data stored in any of areas as shown in  FIG. 3A . That is, it calculates an intra-group average of a blood pressure group including a plurality of pieces of blood pressure data measured under the identical measurement condition for a prescribed measurement condition, e.g., the after-waking-up time slot. Then, first evaluating unit  201  calculates a risk value using the calculated average blood pressure value of intra-blood pressure data group.  
      According to the second calculation example, at least the calculated average of SBP measured after waking up and average of DBP measured after waking up are calculated and presented as the risk values. Preferably, difference values between the calculated average values and respective predetermined threshold values are calculated, and the calculated difference values are presented as the risk values. As to the threshold values herein, for example, the threshold value for average of SBP measured after waking up may be set to 135 mmHg, and the threshold value for average of DBP measured after waking up may be set to 85 mmHg, based on the standard of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure, or based on the hypertension standard of home blood pressure of the Japanese Society of Hypertension. Further, morning hypertension can be determined when average of SBP measured after waking up &gt;135 mmHg and average of DBP measured after waking up &gt;85 mmHg, and the determination result may be displayed.  
      Operation of Electronic Blood Pressure Monitor of First Embodiment  
       FIG. 4  is a flowchart of a main routine executed by CPU  20  of electronic blood pressure monitor  100  of the first embodiment of the present invention. The flowchart of  FIG. 4  is stored in memory  12  in advance as a program, and read and executed by CPU  20 . The process shown in  FIG. 4  is, for example, started when power supply switch  5  is manipulated and power is supplied via power supply unit  25  to CPU  20 .  
      Referring to  FIG. 4 , first, as an initializing process of electronic blood pressure monitor  100 , CPU  20  controls respective units to evacuate the air in air bag  21  to thereby perform a 0 mmHg correction of pressure sensor  14  (step (hereinafter abbreviated as “S”) 1). Next, CPU  20  determines whether measurement time information is stored in a time association table, described later, in memory  12  (S 2 ). When it is stored (YES in S 2 ), subsequently whether there is an instruction of change from the subject (S 3 ). When the instruction of change is sensed (YES in S 3 ), the process goes to S 4 . Otherwise (NO in S 3 ), the process goes to S 6 .  
      On the other hand, if the measurement time information is not stored (NO in S 2 ), the process goes to S 4 . In S 3 , the current measurement time information may be displayed on display unit  4  in order for the subject to determine whether change is necessary. Further, a default value may be stored in the time association table and determination process in S 2  may be omitted. Thus, if the subject is of the normal life pattern, a highly reliable evaluation quantity can be calculated without inputting the measurement time information.  
      In S 4 , time specifying unit  210  of CPU  20  accepts an input of the measurement condition specifying information, that is, measurement time information. Then, CPU  20  records and updates the input measurement time information in the time association table in memory  12  (S 5 ).  
      In S 4 , for example a screen for inputting the measurement time information is displayed on display unit  4 . Specific examples of the screen being displayed are shown in  FIGS. 6A-6C .  
       FIG. 6A  shows an example of accepting an input of the start or end of at least one measurement condition period (measurement time slot) as the measurement time information. On display unit  4 , for example “measurement condition input screen” is displayed, and display for the subject to input wake-up time (for example, 7:00) and sleeping time (for example, 21:00) is provided. Here, it is assumed that the wake-up time is the start of the measurement condition, i.e., the after-waking-up time slot, while sleeping time is the end of the measurement condition, i.e., the before-sleeping time slot. It is assumed that both of them refer to the start, or to the end. Here, it is assumed that time duration is determined in advance separately for each of wake-up time and sleeping time, or determined in advance commonly for wake-up time and sleeping time.  
       FIG. 6B  shows an example of accepting an input of the start and end of at least one measurement condition period as the measurement time information. On display unit  4 , similarly “measurement condition input screen” is displayed, and display for the subject to input the start of wake-up time (for example, 5:30) and the end thereof (for example, 7:00) and the start of sleeping time (for example, 21:00) and the end thereof (for example, 22:00) is provided.  
       FIG. 6C  shows an example of accepting an input of the start or end of at least one measurement condition period and a time duration (a period duration) as the measurement time information. On display unit  4 , similarly “measurement condition input screen” is displayed, and display for the subject to input the wake-up time (for example, 7:00) and the sleeping time (for example, 21:00) and respective time durations (for example, 1:30 and 1:00) is provided. Herein also, it is assumed that the wake-up time is the start of the measurement condition, i.e., the after-waking-up time slot, while sleeping time is the end of the measurement condition, i.e., the before-sleeping time slot. Both may be the start, or the end.  
      In the present embodiment, it is assumed that one or at least two switch(es) included in manipulation unit  300  is/are used for inputting each of the times. For example, the time may be switched by one minute every time memory switch  7  is pressed, and the time being displayed when power supply switch  5  is pressed may be determined as the time where the input is made. It is noted that a not-shown switch for setting time point may be provided, with which each of the times may be input. The screen displayed when inputting the measurement time information is not limited to the manner shown in  FIGS. 6A-6C .  
      Next, exemplary contents of a time association table in which the measurement time information is stored are shown in  FIGS. 7A and 7B .  FIG. 7A  is a first exemplary content of the time association table. In the first example, in the time association table of memory  12 , time data  91  and time duration data  92  are stored in association with and to form pairs with respective measurement conditions of the after-waking-up time slot and before-sleeping time slot. Time duration data  92  may be time duration data being input by the subject, or it may be predetermined time duration data.  
       FIG. 7B  is a second exemplary content of the time association table. In the second example, in the time association table of memory  12 , time slot data  93  is stored to form a pair with each of the measurement conditions of the after-waking-up time slot and before-sleeping time slot.  
      While in the present embodiment the measurement conditions and the measurement time information are associated with each other in the time association table, the storing manner is not limited to such a table format. Further, the time association table may be stored in a prescribed storage area other than memory  12 .  
      Referring to  FIG. 4  again, in S 6 , CPU  20  determines whether measurement switch  6  is manipulated. Until measurement switch  6  is manipulated, determination in S 6  is repeated. When the manipulation of measurement switch  6  is sensed, the process goes to S 8 . It is noted that the order of performing the processes in S 2 -S 5  and the process in S 6  may be reverse.  
      In S 8 , CPU  20  controls respective units to raise the pressure to about the systolic blood pressure of the subject +40 mmHg. Then, it gradually reduces the pressure inside air bag  21  (S 10 ). In this pressure-reducing process, detecting the pressure inside air bag  21  with pressure sensor  14 , blood pressure calculating unit  200  of CPU  20  calculates blood pressure (systolic blood pressure and diastolic blood pressure) values and a pulse rate (S 12 ). Then, the calculated blood pressure values and pulse rate are displayed on display unit  4  (S 14 ). The processes for measuring blood pressure of S 8 -S 12  are the same as those of a conventional electronic blood pressure monitor. While in the present embodiment the blood pressure measurement is performed in the pressure reducing process, it may be performed in the pressure raising process.  
      Next, condition determining unit  209  of CPU  20  obtains time measurement data output from timer  13  to determine the current measurement condition (S 16 ). That is, it refers to the time association table and determines whether the current time point specified by timer  13  belongs to any of the measurement conditions, that is, divisions of measurement time slots.  
      Then, CPU  20  performs a measurement result storing process (S 18 A). The measurement result storing process is described referring to the subroutine of  FIG. 5 .  
       FIG. 5  is a flowchart showing the measurement result storing process in the first embodiment.  
      Referring to  FIG. 5 , data determining unit  211  of CPU  20  determines what the determination result is in S 16  (S 32 ). Then, when the determination result is in the after-waking-up time slot or in the before-sleeping time slot, CPU  20  registers new record R storing the data of pressure value, pulse rate and time point, in an area of memory  12  corresponding to the measurement condition (S 34 ).  
      On the other hand, when the determination result is “other time slot”, that is, when it is determined that there is no applicable measurement condition, the subroutine is ended.  
      Referring to  FIG. 4  again, first retrieving unit  203  of CPU  20  refers to each of areas  26  and  27  of memory  12  to retrieve data of measurement result of the same evaluation day (S 19 ). Then, first determining unit  205  determines whether at least a plurality of prescribed number of pieces of, for example, three, blood pressure data corresponding to each measurement condition are present (S 20 ). While herein the prescribed number is three, the number is not limited thereto so long as the number is at least two.  
      In S 20 , when it is determined that at least three pieces of measurement result data are not recorded for each measurement condition (NO in S 20 ), the series of processes is ended. On the other hand, when it is determined that at least three pieces of measurement result data are recorded for each measurement condition (YES in S 20 ), in accordance with the procedure described above, by first averaging unit  207 , an average value of blood pressure data for each measurement condition is calculated, that is, respective average values of data groups of areas  26  and  27  are calculated (S 22 ). Then, by first evaluating unit  201 , ME average value and ME difference are calculated as the cardiovascular disease risk values (S 24 ). It is noted that, in S 24 , a difference between ME average value and a predetermined reference value as well as a difference between ME difference and a predetermined reference value may further be calculated. Then, the risk value calculation result in S 24  is displayed on display unit  4  (S 26 ).  
      Thus, the series of process is ended.  
      While in the present embodiment the calculation of the average value and the risk value are performed as calculation of the evaluation quantity, at least the average value may be calculated. That is, the average value may be presented (displayed) to the subject as the risk value.  
      Here, an exemplary display of the risk value calculation results in S 26  is shown.  
       FIG. 8  shows a first exemplary display of risk value calculation results (risk determination results). Display areas  53  and  54  of display unit  4  respectively display the calculated ME difference and ME average value as the risk determination results. Each of display areas  53  and  54  displays upper and lower two blocks, between which a line is horizontally displayed. The line indicates a reference value. Therefore, for example when each of the calculated values is higher than the reference value, the block over the line is shown in reversed display (filled display) while the block below the line is shown in non-reversed display (blank display). When it is lower than the reference value, the block below the line is shown in reversed display while the block over the line is shown in non-reversed display. In the example of  FIG. 8 , it is shown that the calculated ME difference is higher than the reference value (20 mmHg) while the calculated ME average is lower than the reference value (135 mmHg).  
      The displaying manner of the risk value calculation results is not limited to the manner of  FIG. 8 . For example, the calculated ME difference value and ME average value may separately be displayed.  
      Also, a difference between respective average values of measurement conditions may be obtained in S 24  and the magnitude relation between them may be displayed in S 26 .  FIG. 9  shows a second exemplary display of the risk value calculation results, showing an exemplary display of correlation between the average values obtained from blood pressure data measured under respective different measurement conditions. In  FIG. 9 , display unit  4  includes display areas  51  and  52  for respectively displaying after-waking-up measurement data and before-sleeping measurement data, as disposed next to each other. On display area  51 , data of average of SBP measured after waking up  61 , data of average of DBP measured after waking up  62 , and data of average of pulse rate PLS measured after waking up  63  obtained by the aforementioned equations are displayed. Next to them, respectively, on display area  52 , data of average of SBP measured before sleeping  71 , data of average of DBP measured before sleeping  72 , and data of average of pulse rate PLS measured before sleeping  73  are displayed. Thus, measurement data of display area  51  and that of display area  52  are displayed in a correlated manner.  
      As to the display of  FIG. 9 , CPU  20  compares the data displayed on display area  51  with that displayed on display area  52 . Based on the comparison result, CPU  20  may implement displaying in a prescribed manner, such as changing the display color for higher blood pressure data to a prescribed color being different from that for lower blood pressure data. For example, CPU  20  may compare data of average of SBP measured after waking up  61  with data of average of SBP measured before sleeping  71  and display data indicative of the higher blood pressure all in a prescribed color.  FIG. 9  is an exemplary display of changing color when data of average of SBP measured after waking up  61  is higher. The displaying manner is not limited to the color changing display, and may be changed to blinking display.  
      As above, in the present embodiment, since the period during which the data of blood pressure of which evaluation quantity is to be calculated is divided by evaluation day basis, the reliability of the evaluation quantity can be improved. Further, the evaluation quantity is calculated only when a plurality of pieces (for example, three) of blood pressure data corresponding to each measurement condition are present, the effect of the psychological variations on the evaluation quantity can be absorbed.  
      Further, since the measurement condition at the pressure measurement is determined based on the time point data from timer  13  and the measurement time information input by the subject, highly accurate evaluation quantity calculation in accordance with the life cycle of the subject is implemented, irrespective of the actual time point.  
      Still further, once the subject sets the measurement time information, it is not necessary for the subject to input the measurement time information from the second time, and therefore the subject of a regular life cycle can be freed from the trouble of operation. From the second time, and when it is not necessary to make a change, time for a series of processes related to the blood pressure measurement can be shortened. Still further, since the time slot corresponding to each measurement condition is fixed (so long as there is no instruction of change) in the first embodiment, the highly reliable evaluation quantity can be presented particularly to the subject of a stable life cycle.  
      It is noted that, information for specifying a measurement condition may be input by the subject every time the measurement is performed. For example, a not-shown switch corresponding to each measurement condition may be provided so that information on the measurement condition corresponding to each switch may be accepted every time the measurement is performed.  
      While in the first embodiment the measurement time information is input before measuring the blood pressure (before calculating the blood pressure), it may be input after measuring the blood pressure (after calculating the blood pressure).  
      While in the present embodiment processes of S 20 -S 26  are performed every time the blood pressure is measured, the main routine may be ended at the process of S 18 A, and the processes of S 20 -S 26  may be performed only in an interrupt process. The processes of S 20 -S 26  may also be performed only when the subject presses a prescribed switch, for example.  
      In the present embodiment, it is assumed that an interrupt process is performed when memory switch  7  is manipulated between prescribed steps. In the interrupt process, for example the measurement results stored in memory  12  are sequentially read and displayed on display unit  4 . The above S 20 -S 26  processes may be performed in the interrupt process also to display the risk values.  
      When risk switch  8  is provided to electronic blood pressure monitor  100 , the manipulation of risk switch  8  may display a risk calculation result of a specific period longer than the evaluation day, for example on a week-by-week basis. Even when risk switch  8  is not provided, this may be performed for example when memory switch  7  is pressed and a prescribed manipulation is performed. A “specific period” is a period that is longer than the evaluation day and that includes a plurality of evaluation days.  
       FIG. 11  is a flowchart showing an interrupt process that is started when risk switch  8  is manipulated.  
      Referring to  FIG. 11 , first determining unit  205  of CPU  20  reads measurement results for the past one week recorded in memory  12  (S 52 ). Then, it determines whether at least three measurement results corresponding to each measurement condition are present, on evaluation day basis (S 54 ), and excludes the evaluation day with less than three measurement results (S 56 ).  
      First averaging unit  207  calculates an average value of blood pressure data for each measurement condition, only for the evaluation day with at least three pieces of blood pressure data for each measurement condition (S 58 ). For example, it may calculate the average value for each evaluation day, and then further average the average values of the evaluation days so that the average value of one week is obtained. It may also possible to collectively calculate, for all the evaluation days other than those excluded in S 56 , the average of blood pressure data of the after-waking-up time slot and the average of blood pressure data of the before-sleeping time slot.  
      Next, first evaluating unit  201  of CPU  20  calculates the risk value on a week-by-week basis based on the average value calculated in S 58  (S 60 ), and displays the risk value (S 62 ). The processes in S 60  and S 62  are the same as in S 24  and S 26  in  FIG. 4 , respectively, and therefore description thereof is not repeated.  
      Thus, when calculating the risk value on a week-by-week basis including a plurality of evaluation days, by increasing the accuracy for each evaluation day, the reliability of the evaluation quantity on a week-by-week basis can consequently be improved.  
      While in the present embodiment the risk value on a week-by-week basis is calculated and displayed when risk switch  8  is manipulated, as described above, the period is not limited to a week so long as it includes a plurality of evaluation days. For example, the risk value may be calculated on a day of the week-by-day of the week basis, a month-by-month basis, a year-by-year basis, a season-by-season basis and the like. Additionally, a plurality of risk switches  8  may be provided respectively corresponding to a week-by-week basis, a month-by-month basis, and a year-by-year basis.  
      When the evaluation quantity is calculated according to the second calculation example also, it can be implemented by the similar procedure as described above. In this case, in S 4 , only the information for specifying a prescribed measuring condition, e.g., the after-waking-up time slot, may be input. In S 20 , whether at least three measuring results corresponding to the prescribed measurement condition are present is determined. In S 22 , the average value for the prescribed measurement condition is calculated.  
      When the evaluation quantity is calculated according to the second calculation example, in S 26 , whether the average value of the blood pressure data corresponding to the prescribed measurement condition is higher or lower than, for example, a prescribed reference value, may be displayed. Determination of the value being higher or lower than the reference value is made by first evaluating unit  201  of CPU  20 . Specifically, when it is determined that the relational expression “systolic blood pressure &gt;135 mmHg or diastolic blood pressure &gt;85 mmHg” or “systolic blood pressure &gt;135 mmHg and diastolic blood pressure &gt;85 mmHg” is satisfied, then it is evaluated that the blood pressure value is higher than a prescribed reference value. When it is determined that the relational expression is not satisfied, then it is evaluated that the blood pressure value is lower than a prescribed reference value. In the relational expression, one of or both of data of average of SBP measured after waking up  61  and data of average of DBP measured after waking up  62  is/are applied as to the measurement condition of the after-waking-up time slot, and one of or both of data of average of SBP measured before sleeping  71  and data of average of DBP measured before sleeping  72  is/are applied as to the measurement condition of the before-sleeping time slot.  
       FIG. 10  shows a display example of the risk calculation result for the blood pressure data in the after-waking-up time slot. In  FIG. 10 , data of average of SBP measured after waking up  64 , data of average of DBP measured after waking up  65 , and average of pulse rate PLS measured after waking up  66  within one evaluation day, as well as an arrow  85 , are shown. CPU  20  compares data of average of SBP measured after waking up  64 , data of average of DBP measured after waking up  65 , and average of pulse rate PLS measured after waking up  66  with respective reference values, and indicates by arrow  85  whether morning hypertension is presumed.  FIG. 10  shows the risk determination result of the case where morning hypertension is presumed, with arrow  85  pointing upwardly. When morning hypertension is not presumed, arrow  85  points downwardly.  
      Further, when the evaluation quantity is calculated according to the second calculation example, in the interrupt process shown in  FIG. 11 , in S 54 , whether at least three measurement results corresponding to a prescribed measurement result are present is determined on an evaluation day-by-evaluation day basis. In S 58 , the average value for the prescribed measurement condition is calculated.  
     Second Embodiment  
      Next, a second embodiment of the present invention is described. The electronic blood pressure monitor according to the second embodiment is similarly structured as in the first embodiment, and therefore description is given using the reference characters for electronic blood pressure monitor  100  in  FIGS. 1 and 2  herein also. In the second embodiment also, description is given assuming that the evaluation quantity is calculated according to the first calculation example described above.  
      In contrast to the first embodiment where all blood pressure data measured under the measurement condition to be the target of evaluation quantity calculation (herein after also referred to as “a specific measurement condition”) is regarded as data for calculating the evaluation quantity (hereinafter referred to as “calculation data”), in the second embodiment, even the blood pressure data measured under the specific measurement condition is not employed as the calculation data, if it does not satisfy a prescribed condition. That is, only when the blood pressure is measured under a specific measurement condition and presumed to satisfy a prescribed condition, the data of the measured blood pressure is used as the calculation data. It is noted that “when it does not satisfy a prescribed condition” is the case where it is presumed that the blood pressure measurement value is affected by psychological variation, e.g., when the subject is deprived of sleep.  
      For example, when an input of information for specifying a measurement condition is accepted every time the blood pressure is measured, it may be applicable to a specified measurement condition irrespective of the measurement time point. However, even when it is determined that the measurement is carried out in the after-waking-up time slot, the reliability of the measurement result itself may be low if the subject is extremely deprived of sleep. In the present embodiment, when sleep deprivation is presumed, the data is not treated as calculation data and whereby a further reliable evaluation quantity can be calculated.  
      In the following, an operation of electronic blood pressure monitor  100  of the second embodiment is described.  
       FIG. 12  is a flowchart of a main routine executed by CPU  20  of electronic blood pressure monitor  100  of the second embodiment. The flowchart of  FIG. 12  is stored in memory  12  as a program in advance, and read and executed by CPU  20 . The processes similar to those in the flowchart of  FIG. 4  have the same reference characters allotted and description thereof is not repeated.  
      Referring to  FIG. 12 , after an initialization process in S 1  is ended, CPU  20  accepts an input of measurement condition specifying information, i.e., measurement time information (S 4 ). In the second embodiment, in S 4 , CPU  20  temporarily records the accepted measurement time information in the internal memory. Then, after the process of S 4  is ended, the processes of S 6 -S 14  described above are sequentially performed. In S 14 , a blood pressure value and a pulse rate are displayed on display unit  4 . In S 16 , based on time point data output from timer  13  and the measurement time information input in S 4 , a present measurement condition is determined by condition determining unit  209 .  
      After the process in S 16  is ended, a measurement result storing process is executed (S 18 B). The measurement result storing process will be described using a subroutine of  FIG. 13 .  
       FIG. 13  is a flowchart showing the measurement result storing process in the second embodiment. Referring to  FIG. 13 , first, condition determining unit  209  of CPU  20  determines what a determination result is in S 16  (S 102 ). When the determination result is the before-sleeping time slot, the process goes to S 110 A. When the determination result is the after-waking-up time slot, the process goes to S 104 A. On the other hand, when the determination result is “other time slot”, the subroutine is ended. The processes shown in S 102  and S 110 A correspond to those in S 32  and S 34  in  FIG. 5 , respectively.  
      In S 104 A, time point specifing unit  210  and time determining unit  212  of CPU  20  retrieve, for example, the latest (last) measurement time point data in the before-sleeping time slot in the same evaluation day stored in memory  12 . Based on the time point data output from timer  13 , an elapsed time is calculated (S 106 ). That is, how many hours have passed since the last measurement time point in the before-sleeping time slot in the same evaluation day is calculated. Then, whether the elapsed time is at least a prescribed time (for example, four hours) is determined (S 108 ). When it is at least a prescribed time (YES in S 108 ), the process goes to S 110 A.  
      In S 110 A, CPU  20  stores in memory  12  data of pressure value, pulse rate and time point in association with the measurement condition.  
      On the other hand, when the elapsed time is less than the prescribed time (NO in S 108 ), the subroutine is ended without recording the measurement result.  
      Referring again to  FIG. 12 , when the measurement result storing process of S 18 B is ended, the processes of S 19 -S 26  as described above are performed, and the series of processes is ended.  
      Thus, in the second embodiment, presuming the last measurement time point in the before-sleeping time slot of the previous day as the sleep time point, whether the subject is deprived of sleep is determined. Then, when the subject is determined to be deprived of sleep, the measurement result is not stored in memory  12  and thus can be excluded from the target of evaluation quantity calculation. This can further eliminate variation in the blood pressure value due to sleep deprivation or the like.  
      In the flowchart shown in  FIG. 13 , while the description have been given assuming that the measurement result in the before-sleeping time slot in the same evaluation day is stored, when the measurement result in the before-sleeping time slot in the same evaluation day is not stored, for example the processes of S 106  and S 108  may be skipped and the process of S 110 A may be performed. Alternatively, since the physical state of the subject at the measurement is unknown if the measurement result in the before-sleeping time slot in the same evaluation day is not stored, the routine may be ended without performing the processes of S 106 -S 110 A.  
      Further, when an evaluation quantity as to the after-waking-up time slot is calculated according to the second calculation example also, the process similar to that described above can be performed by providing the after-waking-up time slot that is a specific measurement condition and the before-sleeping time slot that is not a specific measurement condition, and storing blood pressure data measured in the sleeping time slot. In this case, similarly to the case where the evaluation quantity is calculated according to the first calculation example, it is assumed that the evaluation day includes one before-sleeping time slot and one after-waking-up time slot.  
      In the second embodiment also, the process similar to the interrupt process shown in  FIG. 11  in the first embodiment may be performed. Thus, also on a specific period-by-period basis, such as on a week-by-week basis, further reliable evaluation quantity can be calculated.  
      The measurement result storing process shown in  FIG. 13  may be performed in S 18 A in  FIG. 4  of the first embodiment.  
      While in the foregoing description the measurement result itself is not stored if it does not satisfy a prescribed condition, it may also be possible to perform the following process.  
      First Modification  
      In a first modification of the second embodiment, identification information indicative of whether a prescribed condition is satisfied is recorded in association with measurement result data. In the first modification, electronic blood pressure monitor  100  of the second embodiment has a memory  122  (see  FIGS. 14A and 14B ) in place of memory  12 .  
      The electronic blood pressure of the first modification of the second embodiment is similarly structured as the first embodiment, except for memory  122 , and therefore the reference characters for electronic blood pressure  100  in  FIGS. 1 and 2  are also used for description herein.  
       FIGS. 14A and 14B  show exemplary configuration of memory  122  in the first modification of the second embodiment. Referring to  FIG. 14A , in memory  12 , similarly to the exemplary configuration shown in  FIG. 3 , division of measurement conditions, that is, storage areas  26  and  27  for the before-sleeping time slot and the after-waking-up time slot, respectively, are provided in advance. To each of areas  26  and  27 , a measurement result is stored on a record RR-by-record RR basis. Record RR includes measurement time point data T, systolic blood pressure data SBP, diastolic blood pressure data DBP, pulse rate data PLS, and a calculation flag F that is identification data indicative of whether it is risk calculation data.  
      In the first modification of the second embodiment also, it is not limited to the exemplary configuration of  FIG. 14A  and it may be the configuration as in  FIG. 14B .  
      Referring to  FIG. 14B , in memory  122 , measurement results and measurement condition information are stored in pairs. That is, in  FIG. 14B , record RRi (i=1, 2, 3, . . . , n) in which measurement results and measurement condition information are associated with each other is stored for every blood pressure measurement. In record RRi, measurement time point data Ti, systolic blood pressure data SBPi, diastolic blood pressure data DBPi, pulse rate data PSLi, measurement condition data C 1  or C 2 , and calculation flag F are stored.  
      In the first modification of the second embodiment also, the processes basically similar to those shown in the flowchart of  FIG. 12  are performed by CPU  20 . It is different from the second embodiment in the processes of S 18 B, S 20 B and S 22 . Accordingly, only those processes different from the second embodiment are described in the following.  
       FIG. 15  is a flowchart showing a measurement result storing process in the first modification of the second embodiment. The processes similar to those shown in the flowchart of  FIG. 13  have allotted the same step numbers, and detailed description thereof is not repeated.  
      Referring to  FIG. 15 , similarly to the second embodiment, first, condition determining unit  209  of CPU  20  determines what a determination result is in S 16  (S 102 ). When the measurement condition is the before-sleeping time slot, the process goes to S 204 . On the other hand, when the measurement condition is “other time slot”, that is, when it is determined that there is no applicable measurement condition, the subroutine is ended.  
      When the measurement condition is the after-waking-up time slot, the processes of S 104 A-S 108  described above are performed. In S 108 , when the elapsed time is at least a prescribed time (YES in S 108 ), the process goes to S 204 . On the other hand, if the elapsed time is less than the prescribed time (NO in S 108 ), the process goes to S 202 .  
      In S 202 , CPU  20  sets the value of calculation flag F to 0, and temporarily records the calculation flag F being set to 0. On the other hand, in S 204 , CPU  20  sets the value of calculation flag to  1 , and temporarily records the calculation flag F being set to 1.  
      After the process of S 202  or S 204  is ended, CPU  20  stores in memory  122  data of pressure value, pulse rate, calculation flag value and time point in association with the measurement condition (S 110 B). Thus, the subroutine is ended.  
      As above, in the first modification, all the blood pressure data measured under one of the predetermined measurement conditions is stored. This makes it possible to use the measurement results for a purpose other than the risk value calculation. For example, the measurement results may be sequentially read and displayed.  
      Next, description is given on processes performed in S 20  and S 22  in  FIG. 12  in a second modification of the second embodiment, in place of the processes described in the second embodiment.  
      In the second modification, in S 20 , second retrieving unit  204  and second determining unit  206  determines whether at least three measurement results wherein calculation flag F=1 corresponding to each measurement condition are present. In the following, such a measurement result wherein calculation flag F=1 is referred to as “a calculable measurement result”. That is, whether at least three calculable measurement results are stored for each of the before-sleeping time slot and the after-waking-up time slot is determined. If one of the time slots fails to store the at least three calculable measurement results, then the series of processes is ended. On the other hand, when at least three calculable measurement results for each of the measurement conditions are stored, the process goes to S 22 .  
      In the second modification, in S 22 , second averaging unit  208  of CPU  20  calculates the average value for the calculable measurement results for each measurement condition. Then, based on the average values thus calculated, the processes of S 24 -S 26  including calculation of the evaluation quantity using second evaluation unit  202  are performed.  
      While in the first modification the calculation flag value (0 or 1) is stored in association with the measurement result even when the measured condition is the before-sleeping time slot, the calculation flag value may not be stored.  
      When the evaluation quantity is calculated according to the second calculation example, in S 20 , whether at least three calculable measurement results corresponding to the after-waking-up time slot in the same evaluation day are stored is determined. If at least three calculable measurement results are not stored, the series of processes are ended. If at least three calculable measurement results are stored, the process goes to S 22 . It is noted that, when the evaluation quantity is calculated according to the second calculation example, if the measurement condition is the before-sleeping time slot, the calculation flag value may be set to 0 in S 204 .  
      In the first modification of the second embodiment also, the process similar to the interrupt process shown in  FIG. 11  in the first embodiment may be performed. That is, in S 54 , CPU  20  determines whether at least three measurement results wherein calculation flag F=1 are present. Thus, as to the evaluation quantity of the week-by-week basis also, further reliable evaluation quantity can be calculated.  
      The measurement result storing process shown in  FIG. 15  may be performed in S 18 A shown in  FIG. 4  of the first embodiment.  
      Second Modification  
      In the second embodiment and its first modification, by assuming the time of the latest time point data in the before-sleeping time slot stored in the same evaluation day is assumed to be the sleep time point, whether a prescribed condition is satisfied is determined. In the second modification of the second embodiment, by accepting an input of information for specifying the sleep time point, whether a prescribed condition is satisfied is determined. The “sleep time point” herein refers to the time point at which the subject is assumed to fall asleep.  
      The electronic blood pressure monitor of the second modification of the second embodiment is similarly structured as that of the first embodiment, description is given using the reference characters for electronic blood pressure monitor  100  in  FIGS. 1 and 2  herein also.  
      Electronic blood pressure monitor  100  in the second modification of the second embodiment includes, for example, a sleep time switch  9 . Time point specifying unit  210  of CPU  20  specifies the time point at which sleep time switch  9  is manipulated as the sleep time point. In the second modification, it is assumed that an interrupt process to the main routine shown in  FIG. 4  is performed.  
       FIG. 16  is the flowchart showing the flow of an interrupt process started when sleep time switch  9  is manipulated.  
      Referring to  FIG. 16 , CPU  20  acquires time point data from timer  13  (S 302 ). Based on the acquired time point data, it stores sleep time point data in a prescribed area in memory  12 , for example (S 304 ). Thus, the interrupt process is ended. It is noted that in S 304  data of year, month, day, and time point is stored as the sleep time point data.  
       FIG. 17  is a flowchart showing a measurement result storing process in the second modification of the second embodiment. The processes similar to those in  FIG. 13  used in the second embodiment have allotted the same step numbers, and description thereof is not repeated. The measurement result storing process shown in the following may be performed in SI  8 A in  FIG. 4  of the first embodiment.  
      Referring to  FIG. 17 , in the second modification, the process of SI  04 B is performed in place of the process of S 104 A in  FIG. 13 . That is, in S 104 B, time determining unit  212  of CPU  20  reads sleep time point data of the same evaluation day recorded in memory  12 . Then in S 106 , the elapsed time from the sleep time point is calculated.  
      In the second modification of the second embodiment also, in S 110 A, while data of blood pressure value, pulse rate, and time point is stored in memory, only the blood pressure value and the pulse rate may be stored herein.  
      In the flowchart of  FIG. 17 , while the description has been given assuming that the sleep time point of the same evaluation day is stored, when the sleep time point of the same evaluation day is not stored, for example processes of S 106  and S 108  may be skipped and the process of S 110 A may be performed. Alternatively, since whether the prescribed condition is satisfied cannot be determined if the sleep time point of the same evaluation day is not stored, the routine may be ended without performing the processes of S 106 -S 110 A.  
      Further, as a still another modification, the first modification of the second embodiment and the second modification of the second embodiment may be combined. In this case, in S 108 , when it is determined by time determining unit  212  that the elapsed time from the sleeping time is at least a prescribed time, the value of calculation flag F is set to 0 (S 202 ), similarly to the first modification. In S 108 , if it is determined that the elapsed time from the sleeping time is less than a prescribed time, the value of calculation flag F is set to  1  similarly to the first modification (S 202 ). When the process of S 202  or S 204  is ended, in place of the process of S 110 C, CPU  20  stores in memory  12  the blood pressure value, pulse rate and calculation flag value in association with the measurement conditions.  
      In the second embodiment and its first and second modifications, in storing the measurement results in memory  12 , they are classified based on whether they are used for calculating the evaluation quantity. The measurement results similar to the first embodiment may be stored in record R and classified when calculating the risk value. That is, whether a prescribed condition is satisfied may be determined based on measurement time point data T stored in association with the measurement results in each area of memory  12 . In this case also, a process similar to the interrupt process shown in  FIG. 11  in the first embodiment may be performed. That is, in S 54 , CPU  20  determines whether there are at least three pieces of blood pressure data determined to satisfy a prescribed condition. Thus, a further reliable evaluation quantity can be calculated.  
      The risk value calculation method performed by the electronic blood pressure monitor of the present invention can be provided as a program. The program can be provided as a program product by recording in an optical medium such as a CD-ROM (Compact Disc-ROM) or a computer readable recording medium such as a memory card. Also, the program can be provided by downloading through a network.  
      The provided program product is installed in a program storing unit such as hard disk and executed. It is noted that the program product includes the program itself and the recording medium recording the program.  
      Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.