Proxy reports of physical activity were valid in older people with and without cognitive impairment.
OBJECTIVE
To determine the validity of proxy reports of physical activity in people with symptoms of cognitive impairment.


METHODS
In the Canadian Study of Health and Aging, a multicenter prospective cohort study, someone close to the participant (proxy) reported exercise levels for people who screened positive for cognitive impairment or were institutionalized (n=2421), some of whom were subsequently diagnosed with cognitive impairment (n=1612) and some of whom were diagnosed as having no cognitive impairment (n=809). The reliability and validity of proxy reports of physical activity were examined by agreement with self-reports of physical activity (intraclass correlation coefficient) and by association with adverse health markers (Mantel-Haenzel chi(2)) and survival time (Cox proportional hazards).


RESULTS
Proxy reports of physical activity had moderate interrater reliability (0.55, 95% confidence interval: 0.49-0.61, P<0.001). People in higher physical activity group had fewer adverse health outcomes than those in lower physical activity groups. Predictive validity was confirmed as people who had higher proxy-reported physical activity survived longer that those with lower physical activity.


CONCLUSIONS
Proxy-reported physical activity appears to be a valid estimate of physical activity in people with symptoms or a diagnosis of cognitive impairment.
Middleton
Laura E
LE
Department of Psychiatry, University of California - San Francisco, San Francisco, CA, USA.
Kirkland
Susan A
SA
Mitnitski
Arnold
A
Rockwood
Kenneth
K
D000368:Aged; D002170:Canada / Q000453:epidemiology; D003072:Cognition Disorders / Q000453:epidemiology*; D016001:Confidence Intervals; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D008297:Male; D005082:Physical Exertion; D016016:Proportional Hazards Models; D019727:Proxy; D015203:Reproducibility of Results