Self-reported activities of daily living and performance-based functional ability: a study of congruence among the oldest old

Although researchers and clinicians tend to use subjective evaluations of functioning and objective assessments interchangeably, there may be important differences between how people view their own abilities and objective indicators. This study aims to examine the relation between self-reported evaluations of function and health and performance-based (PB) measures of functional ability and objective health indicators in a sample of the oldest old. The study is based on data from a sample of 349 individuals aged 80 and older from the OCTO-Twin Study. One member of each twin pair was randomly selected for this study. The result demonstrates that subjective evaluations of functional ability are significantly associated with objective measures of health and PB measures of function although considerable variance remained unexplained. The association of PB measures to the self-report evaluations differed by measure. PB measures had stronger associations with self-reported functioning than objective health indicators such as diseases and medications. PB balance was related to self-reported function in instrumental activities in daily life (IADL) and self-reported mobility, whereas PB upper body strength and flexibility was associated with all three self-reports of function but not to perceived health. The strength of these associations did not differ from one another suggesting that PB balance and upper body strength and flexibility have comparable effects on self-reports of daily life function. From a practical perspective, our findings confirm that self-reported ADL reflects objective measures of functioning, but probably also has subjective components that need further exploration. The result also indicates a need for multiple measures in evaluating functional ability in the oldest old.