Cognitive Function Is Associated With the Development of Mobility Impairments in Community-Dwelling Elders

Objective: To examine the association of cognitive function with the risk of incident mobility impairments and the rate of declining mobility in older adults. Design: Prospective, observational cohort study. Setting: Retirement communities across metropolitan Chicago. Participants: A total of 1,154 ambulatory elders from two longitudinal studies without baseline clinical dementia or history of stroke or Parkinson disease. Measurements: All participants underwent baseline cognitive testing and annual mobility examinations. Mobility impairments were based on annual timed walking performance. A composite mobility measure, which summarized gait and balance measures, was used to examine the annual rate of mobility change. Results: During follow-up of 4.5 years, 423 of 836 (50.6%) participants developed impaired mobility. In a proportional hazards model controlled for age, sex, education, and race, each 1-unit higher level of baseline global cognition was associated with a reduction to about half in the risk of mobility impairments (hazard ratio = 0.51, 95% confidence interval: 0.40-0.66) and was similar to a participant being about 13 years younger at baseline. These results did not vary by sex or race and were unchanged in analyses controlling for body mass index, physical activity, vascular diseases, and risk factors. The level of cognition in five different cognitive abilities was also related to incident mobility impairment. Cognition showed similar associations with incident loss of the ability to ambulate. Linear mixed-effects models showed that global cognition at baseline was associated with the rate of declining mobility. Conclusions: Among ambulatory elders, cognition is associated with incident mobility impairment and mobility decline. (Am J Geriatr Psychiatry 2011; 19: 571-580)