30

Journal of Health Science, 54(1) 30–36 (2008)

Headache, Mental Health, and Use of Medical Resources:
Health Diary Study in Japan
Shin Yamazaki,∗,a Shunichi Fukuhara, a Joseph Green, b Osamu Takahashi, cTakuro Shimbo, d Hiroyoshi Endo,e Shigeaki Hinohara, f and Tsuguya Fukui faGraduate School of Medicine and Public Health, Kyoto University, Yoshida-konoe-cho, Sakyo-ku, Kyoto 606–8501, Japan, b Graduate
School of Medicine, University of Tokyo, 7–3–1 Hongo, Bunkyo-ku, Tokyo 113–0033, Japan, c St. Luke’s Life Science Institute, 9–1
Akashi-cho, Chuo-ku, Tokyo 104–8560, Japan, d Research Institute, International Medical Center of Japan, 1–21–1 Toyama, Shinjukuku, Tokyo 162–8655, Japan, e National Institute of Public Health, 2–3–6 Minami, Wako 351–0197, Japan, and f St. Luke’s International
Hospital, 9–1 Akashi-cho, Chuo-ku, Tokyo 104–8560, Japan(Received August 31, 2007; Accepted November 6, 2007; Published online November 12, 2007)

To examine the association between poor mental health state and having headache in the Japanese general
population, and the association between demographic characteristics and use of medical resources among subjects
with headache. The subjects aged 18 through 75 years were chosen from the Japanese general population. We
administered a questionnaire to obtain baseline data, and asked the participants to keep a personal health-diaryduring October 1–31, 2003. The state of mental health (MH) was examined using the SF-8 Health Survey in thebaseline questionnaire. Of the 2371 subjects, 716 had a headache on at least one day during the study period. Of the716, 52 consulted a physician, 475 used other medical resources, and 189 did nothing about the headache. There
was an association between MH score and headache [adjusted odds ratio (OR) = 1.166 (95% confidence interval(CI): 1.010–1.346) for 10-point increment of MH score]. There was also an association between use of medical
resources and having a family physician. Poor mental health was associated with headache in the Japanese general
population, and one of the predictors of consulting a physician among the headache sufferers was having a family
physician whom the subject greatly trusts.
Key words —— headache, health diary, medical resource, mental health, SF-8 Health Survey

INTRODUCTION
Headache is a very common complaint.1–4)
Previous studies showed that headache is associated with depression, stress and anxiety.4–6)
Drugs with antidepressant actions are also effective in the prophylactic treatment of both tensiontype headache and migraine.1) Recent studies also
examined the impact of migraine on functional
health that included mental health (MH) and wellbeing.7–10) However, the association between MH
and headache in Japan is not clear. Moreover, little
is known about the use of medical resources amongindividuals with headache. To find which groups
are at high risk for headache in the Japanese general∗

To whom correspondence should be addressed: Graduate
School of Medicine and Public Health, Kyoto University,
Yoshida-konoe-cho, Sakyo-ku, Kyoto 606–8501, Japan.
Tel.: +81-75-753-4645; Fax: +81-75-753-4644; E-mail:syam@pbh.med.kyoto-u.ac.jp

population, we examined the association between
MH and headache. We also examined the associations between demographic characteristics and theuse of a medical resource for treatment of headache
among the subjects with headache.

MATERIALS AND METHODS
Subjects and Questionnaire —— This study waspart of the prospective health diary study conductedin Japan.11) Ethical approval was obtained from the
Research Ethics Committee of Kyoto University
Graduate School of Medicine, Japan. The method
used for data collection was described by Fukui
et al.11) In brief, a nationally representative panel
comprised of 210000 households, and belonging to
the Japan Statistics & Research Co. Ltd. (Tokyo,
Japan), was used. Taking into consideration thesize of the cities, towns and villages, a population-

No. 1weighted, random sample of 5387 households waschosen. A letter describing this study and requesting the participation of families in the study was
mailed to the 5387 households with a return envelope. Among them, 1867 households agreed to participate in the study. The sample size was adjusted
to 1464 households to make the sample nationally
representative in terms of co-habitation with a family member.
Data were collected from a baseline questionnaire and health diary. The written baseline questionnaire was administered to 3852 individuals in
the 1464 households. The baseline questionnaire included the SF-8 Health Survey (SF-8), age, sex, cohabitants, co-habitation with a family member, morbid conditions, annual household income, employment, and number of working hours. This questionnaire also asked whether the individual had a family
physician and if so, whether the individual highly
trusted the physician or not. A subject was considered to have a family physician whom the subject
greatly trusts if the subject assigned a score of 9
or 10 for the family physician on the 0–10 visual
analogue scale (in which 10 corresponded to having
a physician whom the subject greatly trusts). Information about the location of residence (urban orrural) was obtained from the random sampling process.
We mailed blank health-diary notebooks to
the households. Participants in the households
were asked to fill out baseline questionnaire from
September 18, 2003 until October 3, 2003, and theirown health diary daily from October 1, 2003 until
October 31, 2003. The health diary included the following questions: Did you have any pain or healthsymptoms that made you feel uncomfortable today?
If so, write down your specific symptoms. If you
did have a symptom, did you (i) do nothing aboutit? (ii) consult a person(s) who was not a physician?
(iii) take an over-the-counter (OTC) drug? (iv) takea vitamin or other supplement? (v) use a resourceof oriental medicine? (vi) consult a physician? (vii)
use another medical resource(s)?
We divided the subjects into the following two
groups: the headache group consisted of those whoreported that they had headache symptoms on 1
or more days during the study period, and the noheadache group consisted of the remaining subjects
who did not have a headache during the study period.
We also divided the subjects who had aheadache on one or more days during the 31-day

31

study period into five groups according to the use of
medical resources as follows: (a) consulting physician group: subjects who had a headache for one
or more days during the study period and consulted a physician on one or more days; (b) oriental medicine resources group: subjects who had aheadache on one or more days during the study period, who did not consult a physician, and who useda resource of oriental medicine on one or more days;(c) OTC drug group: subjects who had a headacheon one or more days during the study period, who
did not consult a physician nor use any resource oforiental medicine, and who used an OTC drug on
one or more days; (d) other medical resource group:
subjects who had a headache on one or more days
during the study period, and who did not consult aphysician, did not use an oriental medicine resource,
did not use an OTC drug, but used another medical
resource; (e) doing nothing group: subjects who hada headache on one or more days during the study
period and who did nothing about it. We also defined the ‘using medical resource but not consulting a physician’ (MNP) group as subjects who used
a medical resource but did not consult a physician;this group included the (b), (c) and (d).
The SF-8 Health Survey —— Several instrumentsthat score the mental health state, which were validated scientifically, can detect depressive state. One
such questionnaire is the five-item version of the
Mental Health Inventory (MHI-5).12) The MHI-5
serves as the MH domain of the SF-36 Health
Survey (SF-36), which is one of the widely used,generic, health-related quality of life (HRQOL) instruments and has been translated into Japanese.
13, 14) The SF-8, which is a new, generic, eight-item
assessment, is an alternative form of the SF-36 andgenerates a health profile consisting of eight scales
and two summary measures describing the HRQOL.
The SF-8 relies on a single item to measure each of
the eight domains of health in the SF-36, which arephysical functioning, role limitation due to physical health problems, bodily pain, general health, energy/fatigue, social functioning, role limitation due
to emotional problems, and MH. The SF-8 had been
constructed to provide an even shorter alternative to
the SF-36 for use in large, population-based surveys
of general and specific populations, in which precision is achieved more from sample size than by increasing measurement reliability. By administering
a questionnaire of only eight items, the SF-8 reproduces the eight scales and two summary measuresfrom the SF-36. The SF-8 is the first short-form sur-

32

Vol. 54 (2008)

Table 1. Subjects with or without Headache and Their Use of Medical Resources in October 2003

No headache(a) Headache / Consulting Physician group(b) Headache / OTC Drug groupa)(c) Headache / Oriental Medicine Resources groupa)(d) Headache / Other Medical Resource groupa)(e) Headache / Doing Nothing groupb)

N
2371
1655
52
409
13
53
189

(%)
(100)
(70)
(2)
(17)
(1)
(2)
(8)

a) The MNP group consisted of subjects in (b), (c), and (d) as the group who used a medical resource but
did not consult a physician (n = 475). b) No use of medical resource.

vey to be constructed on the basis of empirical studies linking each item to a comprehensive ‘pool’ of
widely-used questionnaire items proven to measure
the same concept. Because the item pool included
the SF-36 survey, each SF-8 single-item scale andSF-8 summary measures are scored on the same
metrics as the SF-36 scales and summary measures.
The SF-8 was scored using a published algorithm,
i.e., by assigning the mean SF-36 scale score fromthe general Japanese population in 2002 to each response category of the SF-8 measuring the same
concept.15) The score have a mean of 50 and a standard deviation of 10 in the general 2002 Japanese
population. A lower score indicates poorer healthstatus, that is, a lower MH score indicates poorer
MH, and higher tendency for psychological distressand poor well-being.
Statistical Methods —— The subjects were limited
to adults aged 18 through 75 years who filled out
the baseline questionnaire and the diary completely.
In each subject, we determined the number of days
that the subject had a headache or migraine during
the month of October 2003 based on the personal
health diary. We studied the associations between
demographic characteristics and having a headache
using the chi-square test. Next, we used a logistic
regression model to calculate the odds ratio (OR)for poor MH for the headache group compared to
the no-headache group. Adjustments were made forage, sex, co-habitants, co-morbid conditions, household income, number of working hours, and location of residence.
In the second analysis, we investigated factors
associated with using a medical resource for theirheadache among those subjects who had a headacheon one or more days. That is, using multivariate logistic regression analysis, we estimated the ORs of
having a co-habitant(s), having a co-morbid condition(s), level of household income, number of working hours, location of residence, MH score, andthe number of days of having a headache in the

Table 2. Number of Days with Headache Symptoms during
the 31-day Period

None
1 day
2 days3 days
4–6 days
7 days or over

N
2371
1655
325
157
82
108
44

(%)
(100)
(70)
(14)
(7)
(3)
(5)
(2)

consulting-physicians group, and in the MNP groupcompared with the doing-nothing group.

RESULTSThe baseline questionnaire was administered to3852 individuals in 1464 households. Among them,3477 individuals in 1286 households filled out thequestionnaire completely. After excluding individuals aged less than 18 years (N = 1026) or forother reasons (N = 80), there were 2371 eligible
subjects. Among the 2371 individuals, 716 (30%)
had a headache on one or more days during thestudy period. With respect to utilization of healthservices, among the 716 subjects, 52 consulted aphysician for their headache on one or more days,
475 used a medical resource but did not consult aphysician, and 189 did nothing (Table 1). Table 2
shows the distribution of the number of days that the
subjects had a headache. Of the 716 subjects who
had a headache, 234 had a headache on 3 or moredays during the study period. The demographic
characteristics of the 2371 subjects are summarizedin Table 3. The headache group was significantly
younger than the no-headache group [41 [standard
deviation (S.D.)= 14] years vs. 47 (S.D. = 16) years;
p < 0.0001]. The MH score of the headache groupwas significantly lower than that of the no-headachegroup [47 (S.D. = 7) vs. 49 (S.D. = 7); p < 0.0001].

33

No. 1

Table 3. Demographic Characteristics of the Subjects
Total
N
(%)
2371 (100)No-headache groupa)
N
(%)
1655
(100)

Headache groupa)
N
(%)
716
(100)

1065
1306

(45)
(55)

870
785

(53)
(47)

195
521

(27)
(73)

480
483
506
362
540

(20)
(20)
(21)
(15)
(23)

296
312
338
261
448

(18)
(19)
(20)
(16)
(27)

184
171
168
101
92

(26)
(24)
(23)
(14)
(13)

385
1986

(16)
(84)

246
1409

(15)
(85)

139
577

(19)
(81)

1635
736

(69)
(31)

1110
545

(67)
(33)

525
191

(73)
(27)

857
393
571
467
83

(36)
(17)
(24)
(20)
(4)

600
245
409
345
56

(36)
(15)
(25)
(21)
(3)

257
148
162
122
27

(36)
(21)
(23)
(17)
(4)

367
1669
261
74

(15)
(70)
(11)
(3)

241
1178
177
59

(15)
(71)
(11)
(4)

126
491
84
15

(18)
(69)
(12)
(2)

1915
456

(81)
(19)

1331
324

(80)
(20)

584
132

(82)
(18)

< 0.001

Sex
Male
FemaleAge (years old)
18–29
30–39
40–49
50–59
60–75
Co-habitation with family member
Living alone
Other
Diagnosed medical conditions
No
Yes
Number of working hours
Does not work
1–24 hr/week
25–48 hr/week
49 hr or more/week
Missing data
Annual household income (million yen)
< 300
300–999
 1000Missing data
Location of residence
Urban
Rural

p

< 0.001

0.006

0.003

0.004

0.060

0.517

a) The headache group included subjects who had a headache on one or more days, and the no-headache group included theremaining subjects.

The associations between demographic characteristics and having headaches on crude analysis are also
shown in Table 3.
Table 4 shows the results of adjusted analysis.
The significant associations between headache andsex, age, and co-habitation status remained after
the adjustments. We also observed a significant association between the MH score on the SF-8 andheadaches [OR = 1.166 (95% confidence interval(CI): 1.010, 1.346) for 10-point increment of MHscore].
In the second analysis, we examined the associations between demographic characteristics andthe use of a medical resource among the subjects
who had a headache on one or more days during thestudy period. We observed significant associations
between the number of days of headache and using
an OTC drug or other medical resource [adjusted

ORs of one-day increment of headache were 1.305(95% CI: 1.146, 1.486), and 1.640 (95% CI: 1.320,
2.037) for consulting a physician] (Table 5). Moreover, we observed an association between consulting a physician and having a family physician. The
OR for having a family physician whom the subject
does not greatly trust (score > 9) was 2.648 (95%
CI: 1.059, 6.618), and the OR for having a family
physician whom the subject greatly trusts (score >9) was 3.901(95% CI: 1.213, 12.54) compared withthe group who did not have a family physician (Table 5).

DISCUSSION
In this study, we observed significant associations between having headaches and sex, age, co-34Vol. 54 (2008)

Table 4. Results of Adjusted Analysis of the Associations between Risk Factors andHaving Headaches
ORsa)(95% CI)

1.000
3.400∗(Ref.)(2.646, 4.369)

2.851∗
3.084∗
2.754∗
1.885∗
1.000(2.012, 4.040)(2.146, 4.434)(1.916, 3.958)(1.296, 2.740)(Ref.)

1.393∗
1.000(1.045, 1.858)(Ref.)

1.000
0.890

(Ref.)(0.704, 1.125)

0.872
1.000
0.876
1.090

(0.661, 1.150)(Ref.)(0.641, 1.197)(0.762, 1.561)

0.955
0.782
1.000

(0.644, 1.417)(0.575, 1.063)(Ref.)

1.000
0.919
1.166∗(Ref.)(0.719, 1.176)(1.010, 1.346)

Sex
Male
FemaleAge (years old)
18–29
30–39
40–49
50–59
60–75
Co-habitation with a family member
Living alone
Other
Diagnosed medical conditions
No
Yes
Number of working hours
No work with wages
1–24 hr/week
25–48 hr/week
49 hr/week or overAnnual household income (million yen)
< 300
300–999
 1000Location of residence
Urban
Rural
MH (10-point decrease)a) Odds ratios of each risk factor for having headaches on one or more days during the 31day period (headache group vs. no-headache group) using multivariate logistic regression analysis.
Independent variables in the logistic regression model were sex, age, co-habitation with a family
member, diagnosed medical conditions, number of working hours, annual household income, location of residence, and MH score on the SF-8. ∗ p < 0.05.

habitation status, and MH in both crude analysis andadjusted analysis. With respect to factors related tousing medical resources among the headache sufferers, we showed that one of the predictors of consulting a physician among the headache patients washaving a family physician whom the subject greatly
trusts.
Thirty percent of the subjects in our study had aheadache on one or more days during a 31-day period (Table 2). With respect to utilization of healthservices by the headache sufferers in this study (N =716), 57% used an OTC medicine and 7% visited a
primary care physician’s office or the hospital (Table 1). Sakai and Igarashi2) reported that 56% of
their subjects had a recurrent headache in the past
one year in a population-based, nationwide survey
in Japan. The prevalence of migraine was 8%. They

also studied health service utilization by the migraine sufferers. Among the respondents, 57% used
an OTC medicine, 3% visited a primary care physician’s office or hospital regularly, and 12% visiteda primary care physician’s office or hospital once or
twice in the past year. The previous survey asked individuals about their symptoms of headache in thepast one year. Therefore, we cannot directly compare the prevalence of headache among our study
subjects with the prevalence of headache among the
subjects in the study of Sakai and Igarashi2) because
they studied the prevalence over one year, while westudied the prevalence over a month. The method
used in our study, i.e., a prospective health diarystudy, has been shown to increase the likelihoodthat respondents will report most of their symptoms.16, 17) Another advantage of health diary sur-

35

No. 1

Table 5. Results of Multivariate Logistic Regression Analysis to Examine the Associations between the Use of Resources for Headacheand Factors among the Subjects with Headache (N = 716)a)
MNP groupb) (N = 475)
compared with doing nothingc)(N = 189)
OR(95% CI)

Consulting a physician (N = 52)
compared with doing nothingc)(N = 189)
OR(95% CI)

1.000
1.349

(Ref.)(0.819, 2.220)

1.000
0.656

(Ref.)(0.218, 1.976)

1.075
1.157
1.703
0.931
1.000

(0.546, 2.116)(0.567, 2.361)(0.829, 3.495)(0.448, 1.933)(Ref.)

1.069
1.011
0.714
0.419
1.000

(0.300, 3.808)(0.259, 3.951)(0.165, 3.088)(0.085, 2.059)(Ref.)

0.847
1.000

(0.500, 1.435)(Ref.)

1.639
1.000

(0.562, 4.782)(Ref.)

1.000
1.092

(Ref.)(0.679, 1.757)

1.000
1.483

(Ref.)(0.600, 3.662)

1.011
1.000
1.217
1.242

(0.613, 1.669)(Ref.)(0.685, 2.160)(0.631, 2.442)

0.857
1.000
0.614
0.942

(0.306, 2.402)(Ref.)(0.178, 2.121)(0.212, 4.183)

1.514
1.490
1.000

(0.748, 3.065)(0.858, 2.585)(Ref.)

0.689
0.969
1.000

(0.158, 3.001)(0.317, 2.965)(Ref.)

1.000
0.926
0.808
1.305∗(Ref.)(0.581, 1.477)(0.605, 1.077)(1.146, 1.486)

1.000
1.174
0.934
1.640∗(Ref.)(0.455, 3.030)(0.543, 1.607)(1.320, 2.037)

1.000
1.080

(Ref.)(0.680, 1.716)

1.000
2.648∗(Ref.)(1.059, 6.618)

1.349(0.714, 2.546)

3.901∗(1.213, 12.542)

Sex
Male
FemaleAge (years old)
18–29
30–39
40–49
50–59
60–75
Co-habitation with a family member
Living alone
Other
Diagnosed medical conditions
No
Yes
Number of working hours
No work with wages
1–24 hr/week
25–48 hr/week
49 hr or more/week
Annual household income (million yen)
< 300
300–999
 1000Location of residence
Urban
Rural
MH (10-point decrease)
No. of days with headache (1-day increase)
Having a family physicianNo
Yes, a family physician whom
the subject does not greatly trustd)
Yes, a family physician whom
the subject greatly trustsd)a) The independent variables in the logistic regression model were sex, age, co-habitation with a family member, diagnosed medical conditions,
number of working hours, annual household income, location of residence, MH score on the SF-8, number of days of having headache in October
2003, and having a family physician. b) MNP group: using a medical resource but not consulting a physician. c) Doing nothing: no medical resourceuse. d) A subject was considered to have a family physician whom the subject greatly trusts if the subject assigned a score of 9 or 10 for the family
physician on the 0–10 visual analogue scale (10 for having a physician whom the subject greatly trusts). ∗ p < 0.05.

veys is that it minimizes recall bias compared witha questionnaire that requires subjects to remember
his/her symptoms over the past 1 year or past 1
month. These evidences suggest that there are many
headache sufferers in Japan and that many headache
sufferers use OTC medicines and are not given adequate medical information from physicians.
We clarified the major risk factors for headache(female, aged 18 years through 59 years, living

alone, and lower mental health). Providing appropriate health instructions at the time of healthcheckup or when an occupational health survey
is performed, might be effective in improving thehealth of individuals.
There were some limitations in this study. We
used a health diary, headache was self-reported, andwe could not classify the type of headache. That is,
the health diary we used in this study was not a spe-

36Vol. 54 (2008)

cific headache diary and did not include information
about headache intensity and associated symptoms.
Therefore, it was not possible to establish a more
specific headache diagnosis. Furthermore, the information in the diary about headache was not validated. Second, although the demographic characteristics of the subjects were similar to those obtainedin the national census in Japan, the participation ratein this study was very low. We could not rule outthat selection bias did not affect our results. Third,
we are unable to discuss cause-effect relationships
between MH and headache because we analyzed thedata of this prospective health diary study as a crosssectional survey. Despite these limitations, the results of this study are still valuable because there
have been only a few studies that examined the association between MH and headache in the Japanesegeneral population and the association between demographic characteristics and the use of medical resources by headache sufferers.
In conclusion, poor mental health was associated with headache in the Japanese general population, and one of the predictors of consulting aphysician among the headache sufferers was having
a family physician whom the subject greatly trusts.
Acknowledgement The research reported in thisarticle was supported, in part, by grants from the St.
Luke’s Life Science Institute, Tokyo, Japan.

REFERENCES
1) Raskin, N. H. (2005) Headache. In Harrison’s Principles of Internal Medicine, 16th ed. (Kasper, D.
L., Braunwald, E., Fauci, A. S., Hauser, S. L.,
Longo, D. L. and Jameson, J. L., Eds.), McGrawHill, New York, pp. 85–94.
2) Sakai, F. and Igarashi, H. (1997) Prevalence of migraine in Japan: a nationwide survey. Cephalalgia,
17, 15–22.
3) Takeshima, T., Ishizaki, K., Fukuhara, Y.,
Ijiri, T., Kusumi, M., Wakutani, Y., Mori, M.,
Kawashima, M., Kowa, H., Adachi, Y., Urakami,
K. and Nakashima, K. (2004) Population-based
door-to-door survey of migraine in Japan: theDaisen study. Headache, 44, 8–19.
4) Henry, P., Auray, J. P., Gaudin, A. F.,
Dartigues, J. F., Duru, G., Lanteri-Minet, M.,
Lucas, C., Pradalier, A., Chazot, G. andEl Hasnaoui, A. (2002) Prevalence and clinicalcharacteristics of migraine in France. Neurology,

59, 232–237.
5) Zwart, J. A., Dyb, G., Hagen, K., Odegard, K. J.,
Dahl, A. A., Bovim, G. and Stovner, L. J. (2003)
Depression and anxiety disorders associated withheadache frequency. The Nord-Trondelag HealthStudy. Eur. J. Neurol., 10, 147–152.
6) Wacogne, C., Lacoste, J. P., Guillibert, E.,
Hugues, F. C. and Le Jeunne, C. (2003) Stress, anxiety, depression and migraine. Cephalalgia, 23, 451–
455.
7) Turner-Bowker, D. M., Bayliss, M. S., Ware, J. E.
and Kosinski, M. (2003) Usefulness of the SF-8
Health Survey for comparing the impact of migraine
and other conditions. Qual. Life Res., 12, 1003–
1012.
8) Meletiche, D. M., Lofland, J. H. and Young, W. B.
(2001) Quality-of-life differences between patientswith episodic and transformed migraine. Headache,41, 573–578.
9) Monzon, M. J. and Lainez, M. J. (1998) Quality oflife in migraine and chronic daily headache patients.
Cephalalgia, 18, 638–643.
10) Osterhaus, J. T., Townsend, R. J., Gandek, B. andWare, J. E. (1994) Measuring the functional status
and well-being of patients with migraine headache.
Headache, 34, 337–343.
11) Fukui, T., Rhaman, M., Takahashi, O., Saito, M.,
Shimbo, T., Endo, H., Misao, H., Fukuhara, S. andHinohara, S. (2005) The ecology of medical care in
Japan. Jpn. Med. Assoc. J., 48, 163–167.
12) Berwick, D. M., Murphy, J. M., Goldman, P. A.,
Ware, J. E., Barsky, A. J. and Weinstein, M. C.
(1991) Performance of a five-item mental healthscreening test. Med. Care, 29, 169–176.
13) Fukuhara, S., Bito, S., Green, J., Hsiao, A. andKurokawa, K. (1998) Translation, adaptation, andvalidation of the SF-36 Health Survey for use inJapan. J. Clin. Epidemiol., 51, 1037–1044.
14) Fukuhara, S., Ware, J. E., Kosinski, M., Wada, S.
and Gandek, B. (1998) Psychometric and clinicaltests of validity of the Japanese SF-36 Health Survey. J. Clin. Epidemiol., 51, 1045–1053.
15) Fukuhara, S. and Suzukamo, Y. (2004) Manual of
the SF-8 Japanese version (in Japanese), Institutefor Health Outcomes and Process Evaluation Research, Kyoto.
16) Kooiker, S. E. (1995) Exploring the iceberg of morbidity: a comparison of different survey methods forassessing the occurrence of everyday illness. Soc.
Sci. Med., 41, 317–332.
17) Verbrugge, L. M. (1980) Health diaries. Med. Care,18, 73–95.