This analysis employs data from the Longitudinal Study on Aging (LSOA) an offshoot of the National Health Interview survey (NHIS) jointly sponsored by the National Center for Health Statistics (NCHS) and the National Institute on Aging (NIA). The LSOA is an extended follow-up of elderly persons originally sampled in 1984. For the present analysis, we are using data on outcomes from the follow-up wave of 1986 and baseline data from the first wave. We have constructed two working data files: one for the analysis of mortality (N=4571) and one for the analysis of institutionalization in nursing homes (N=4184). Each data set contains information on the outcome plus baseline data on caregiving arrangements, social and demographic characteristics, and health status.
The baseline data constitute the 1984 Supplement on Aging (SOA) to the NHIS. Investigators at NCHS designed this supplement to answer some of the concerns among policy makers and researchers regarding the increasing proportion of older people in the U.S. population and the need for alternatives to institutionalization.
The sample is based on NHIS procedures. The NHIS employs a multistage probability sample design that permits a continuous sampling of the civilian non-institutionalized population of the United States. Geographical areas of the country are clustered into strata having similar characteristics. From each strata one small area is sampled and a small cluster of housing units is selected to be contacted. In a selected household, all family members are included in the sample. In 1984, 41,471 eligible households were in the NHIS sample. Interviews were conducted in 39,996 of these households, yielding data on 105,290 persons of all ages who resided in them at the time of the interview (Kovar and Poe, 1985). The SOA sampled all persons aged 65 years and over (as well as half those aged 55-64). The final results of the sampling produced 11,497 interviews with persons aged 65 and over.
In general, the survey sought information about each person that would be reported most reliably by the sample person. Self-response is the rule in the SOA. However, for cases in which the sample person was physically or mentally unable to respond, the field staff accepted as a proxy an adult, preferably living in the household (Fitti and Kovar, 1987).
The LSOA design proposes to follow persons in the SOA through 1992, with NCHS conducting re-interviews at two-year intervals, ascertaining mortality, and linking data to Medicare utilization files. In 1986, the re-interview sample consisted of all black elderly over 70 years of age, half of all white elderly aged 70-79, and all white elderly aged 80 years or older. The 1986 follow-up interview used computer-assisted telephone interviewing (CATI). During the baseline contact, interviewers had asked respondents for a telephone number and address for themselves and a contact person. A letter explaining the study preceded the telephone call. This allowed persons who could not answer for themselves to discuss the information with proxy respondents. The field staff sent a self-administered mail questionnaire to respondents who could not be reached by telephone. The staff also administered a decedent follow-up questionnaire to the contact person or next-of-kin of respondents who had died. This interview ascertained date and place of death, hospitalization or nursing home use in the last year of life.
The eligible population for follow-up was 5151, of which the field staff ascertained the vital status of 4734 (91.9%). Among these, 604 people, or 11.7% of eligible respondents, were deceased. The field staff completed interviews with 99.6 percent of living eligible respondents or their proxies, and with 90.7 percent of the contacts for deceased eligible people.