Low cognitive performance, comorbid disease, and task-specific disability: findings from a nationally representative survey

Abstract

Background: This research evaluated the association of low cognitive performance with both chronic diseases and conditions, and with difficulties in a broad array of task-specific functioning and disability measures in older adults living in the community.

Methods: Data were from the first wave of the Assets and Health Dynamics Among the Oldest-Old Study, a national panel survey of individuals age 70 and older (n = 6600 age-eligible self-respondents). Low cognitive performance (LCP) was defined as scores in the lowest (poorest performing) 25th percentile of a cognitive performance scale. The associations of LCP with prevalent chronic diseases and conditions and with limitations in 14 tasks (strength and mobility, instrumental activities of daily living, and activities of daily living) were evaluated. Associations of LCP and task limitations were adjusted for potential modifiers and confounders, including demographic characteristics (age, gender, race), educational attainment, chronic diseases, depressive symptoms, and sensory impairments. Data were weighted to account for complex sample design and nonresponse.

Results: More than one third of people with LCP had three or more coexisting diseases and conditions. The unadjusted associations of LCP with task functioning were attenuated after covariate adjustment, but even after adjustment, LCP remained significantly and independently associated with functioning problems in 9 of 14 tasks (borderline with four more), including mobility tasks.

Conclusions: Low cognitive performance, regardless of its relationship to clinical dementia, coexists with multiple chronic diseases and conditions. It is independently associated with a broad array of functioning difficulties, even after controlling for demographic characteristics, educational attainment, and chronic conditions. Chronic diseases and conditions, however, attenuate the relationship between LCP and some task difficulties. LCP should be considered an important comorbid condition associated with both chronic diseases and disability that substantially increases the health burden of many older adults who are poorly equipped to handle it.