Performance-based physical function and future dementia in older people

Background: The association of physical function with progression to dementia has not been well investigated. We aimed to determine whether physical function is associated with incident dementia and Alzheimer disease (AD). Methods: We performed a prospective cohort study of 2288 persons 65 years and older without dementia. Patients were enrolled from 1994 to 1996 and followed up through October 2003. Main outcome measures included incident dementia and AD. Results: During follow-up 319 participants developed dementia (221 had AD). The age-specific incidence rate of dementia was 53.1 per 1000 person-years for participants who scored lower on a performance-based physical function test at baseline (<= 10 points) compared with 17.4 per 1000 person-years for those who scored higher (< 10 points). A 1-point lower performance-based physical function score was associated with an increased risk of dementia (hazard ratio, 1.08; 95% confidence interval, 1.03-1.13; P <.001), an increased risk of AD (hazard ratio, 1.06; 95% confidence interval, 1.01-1.12; P=.01), and an increased rate of decline in the Cognitive Ability Screening Instrument scores (0.11 point per year; 95% confidence interval, 0.08-0.14; P <.001) after adjusting for age, sex, years of education, baseline cognitive function, APOE epsilon 4 allele, family history of AD, depression, coronary heart disease, and cerebrovascular disease. Conclusions: Lower levels of physical performance were associated with an increased risk of dementia and AD. The study suggests that poor physical function may precede the onset of dementia and AD and higher levels of physical function may be associated with a delayed onset.