Does subjective health matter? Predicting overall and specific ADL disability incidence

The aims of this study were to examine the incidence of activities of daily living (ADL) and instrumental activities of daily living (IADL) disability in a national sample of community-living older adults, and to evaluate the value of baseline self-rated health (SRH) in predicting these outcomes. Additionally, we investigated whether SRH's prognostic ability extended to individual ADL/IADL components (e.g. bathing, managing money).

Data were obtained from the 2014 and 2016 Korean Longitudinal Study of Aging (N = 3431). Respondents were aged 65+ and non-disabled at baseline. Setting the respondents with "very good" or "good" baseline SRH as the reference group, logistic regression models were applied to analyze the association between SRH and disability risk.

The overall incidence rates for ADL and IADL were 25.6 and 53.4/1000 person-years, respectively. Disability incidence increased significantly with poorer SRH. In multivariable regressions, subsequent 1 + ADL disability was significantly associated with "bad" (OR 2.86) and "very bad" SRH (OR 4.28). SRH also predicted 1 + IADL disability for respondents who reported "moderate", "bad", or "very bad" health (OR 2.01-3.39). SRH was predictive of three out of five ADL components, and seven out of 10 IADL components.

SRH predicted functional decline after two years in older adults without baseline disabilities, and its prognostic ability extended to individual ADL/IADL components. Patterns of SRH-morbidity associations can help health administrators identify those at risk of subsequent functional decline. Early interventions targeted at those with poor SRH can help alleviate the strain on long-term care support systems.