Multimorbidity groups based on numbers of chronic conditions are associated with daily activity.

Objective: Instrumental activities of daily living (IADL) are important for managing multiple chronic conditions (MCC) and maintaining independence while aging. Using data from the National Health and Aging Trends Study (NHATS), we answered the question: are there differences in ability and performance of IADL among groups of older adults with 0-1 (no MCC), 2-4 (low MCC), and 5+ chronic conditions (multisystem morbidity: MM)?

Methods: Cross-sectional study using Poisson regression and incidence rate ratios. Participants were 6,019 community-dwelling older adults who regularly take medications. We derived composite variables for ability and performance of IADL; MCC groups were based on count of 11 chronic conditions.

Results: Older adults with MM had lower IADL count for ability (IRR = .81) and performance (IRR = .77), and MM group significantly predicted both ability and performance of IADL (p < .001); 'low MCC' group was not significantly different than 'no MCC' regarding disability.

Discussion: Having MM is statistically and clinically different than having low MCC or no MCC; 5+ chronic conditions may be a meaningful inclusion criterion for interventions to decrease disability and 2-4 chronic conditions may be better for trials to prevent disability. Researchers should measure both ability and performance of daily activity.