Cognitive impairment as a strong predictor of incident disability in specific ADL-IADL tasks among community-dwelling elders: the Azuchi Study.

PURPOSE

We examined differential effects of cognitive impairment on each of the activities of daily living (ADL) and instrumental activities of daily living (IADL) tasks.

DESIGN AND METHODS

In a 3-year follow-up of community-dwelling elderly persons in Azuchi, Japan, we assessed cognition by using the Hasegawa Dementia Scale. We examined (a) the cross-sectional association between cognitive impairment and functional disability in each ADL-IADL item; (b) cognitive impairment as a risk factor for incident disability in each ADL-IADL item, through logistic regression models; and (c) probabilities of incident loss of ADL-IADL abilities or death in 3 years, using multinomial logistic regression models. We also calculated the population attributable risk (PAR%) of cognitive impairment on incident loss of task-specific ADL-IADL abilities.

RESULTS

Cross-sectionally, the severity of cognitive impairment was associated with disability in each ADL-IADL task, with larger effects shown for ADL items. Longitudinally, minimally or mildly cognitively impaired individuals had a significantly higher risk of losing functional abilities compared with those with intact cognition. The PAR% indicated that cognitive impairment accounts for 11% to 36% of incident disability in ADL-IADL tasks, with the highest PAR% shown for the ability to feed oneself.

IMPLICATIONS

Cognitively impaired subjects are heterogeneous; the severity of cognitive impairment has a different impact on incident loss of task-specific ADL-IADL abilities, and comorbidities could affect disabilities differently. Consideration of these heterogeneities will enrich future studies on the impact of cognitive impairment on ADL-IADL abilities.