Relationship of Methods of Admission to Length of Stay in State Hospitals (1963)

D URING the last 15 years considerable interest has developed in statistical analysis of mental hospital population movement for better understandilng of patterns of hospitalization and, less frequently, for assessing local administrative practices and methods of treatment. Among the various biostatistical techniques which have been applied to this problem, life-table methodology, in the form of cohiort followup analysis, has proved especially useful ini studies such as the analysis of 40 years of population movemelnt in a State hospital for the mentally ill (1), the analysis and comparison of population movemenit for 11 different State hospital systems (2), the measurement of longterm trends in the release rate of schizophrenic patients (3), anid the alnalysis; of population movement in a hospital fofr the mentally retarided (4), to mention only a feiw of the large number olf such investigations which have been publislhed. Specific techniiques vary, depending on the question under investigation; some of these were described and evaluated in a recent paper on cohort follow-up methodology (5). The typical cohort followup study analyzes the population movement of a large group of patients admitted for the first time over a fixed calendar period ranging from a few months to several years. The group is first stratified into relatively homogeneous subgroups or cohorts by such omnipresent criteria as age, sex, and clinical diagnosis. Each patient in each cohort is then classified according to the length of time elapsing from date of admission to the date of each significant clhange in his hospitalization status, such as placement on convalescent leave, return from leave, direct discharge, readmission, or death. With this information the different cohorts can be compared with respect to the percentage of each starting cohort still in the hospital or, alternatively, the percentage released at stated intervals after the first admission. The usual practice has been to follow each first admission only to the point of his first significant release from the hospital. This paper differs from the typical study ill two important respects. First, stratification of each sex group of first admissions is based on legal classification, the method of admission unider wlich the patient first entered the California State mental hospital system, rather than on some of the more customary parameters. Second, each patient is followed as an individual for a period of 24 months from date of first admission, irrespective of the number of movements in and out of the hospital whicl lhave occurred during that time and irrespective of changes in his case number. (In the California State mental hospital system as in many other State systems, each readmission is assigned a new case number, a practice which complicates the followup of an individual through one or more readmissions.) Within this framework there are many possible lines of investigation. For example, for a colhort of patients first admitted on a volunMr. Morgan is statistical research officer an,d Mr. Cook is data processing analyst, California State Department of Mental Hygiene, Sacramento. The investigation was supported in part by research grants from the National Institute of Mental Health (MY-1950) and the California State Department of Mental Hygiene (R-59-17, No. 5).