Challenges in Research on the Oldest Old: The Example of Inequalities in Functional Health

Abstract

The general relevance of health in old age is in stark contrast to the low number of population-based surveys that include the oldest old. The exclusion of older people with health impairments from population-based surveys has consequences for evidence on health inequalities among the oldest old. This article aims (1) to analyse socioeconomic inequalities in functional health in the oldest old, and (2) to discuss methodological challenges related to surveys in this age group. We used data from the population-based study “Old Age in Germany” (D80+), explicitly including persons living in private households and nursing homes and those experiencing health impairments. In total, 10,578 persons aged 80 years and older participated in the study. We initially focused on the association between educational level and functional health (instrumental activities of daily living). Subsequently, we explored in a set of sensitive analyses (different regression models) how methodological and design decisions impact these results. The results showed inequalities in functional health among the oldest old. Functional limitations were higher in persons with lower education. Sensitivity analyses revealed that when persons who participated via proxy due to health impairments were excluded, no health inequalities were observed anymore. However, they could be observed when persons living in nursing homes were excluded or when different indicators of functional health or socioeconomic resources were used. A high item nonresponse rate constituted a major challenge of the analyses. Our results stress the importance of implementing a methodological approach that explicitly includes the oldest old with health impairments in surveys when analysing health inequalities in this age group.