Longitudinal patterns of formal and informal social support in an urban elderly population.

Stability and change in the use of formal and informal social support was assessed over a three year period among a representative sample of 1855 elderly urban participants in a longitudinal study of aging and health. Whether people received informal, formal, both types of support or no support was determined in baseline, 12 and 24 month personal interviews. Most respondents retained the same form of support across all three interviews. The extent of stability or change varied according to the form of support reported at baseline. Two-thirds of those with no social support continued without support and 40% of those using both informal and formal support continued to do so at subsequent assessments. The substitution of formal for informal support was infrequent and not statistically significant. Pair wise discriminant function analyses of groups of respondents with the most frequent longitudinal support patterns were performed to identify baseline health and social characteristics associated with stable use, the addition of another form of support or change to nonuse, over time. Changes in the use of support were influenced more by initial levels of health and functional status than by social and economic circumstances. Larger proportions of respondents dropped use of support then added an additional form of support. Respondents using both formal and informal support at baseline died across time in higher proportions than those in other support categories. The extent of stability in support use and nonuse, the character of changes in support use across time and greater attrition among those who were the heaviest users of support, serve to create a relative balance in the use of informal and formal support in this aging cohort, at least over the time frame over which respondents were followed in this study.