Reliability and validity of questions about exercise in the Canadian Study of Health and Aging.

Regular exercise in elderly people has beneficial health effects. We examined exercise frequency and intensity from the Canadian Study of Health and Aging Risk Factor Questionnaire (RFQ). The reliability and validity of these two questions individually, and when combined to form a scale, are reported. Agreement between the self-administered RFQ and an interviewer-administered Add-on Study was examined using intraclass correlations, which were 0.80 for frequency (95% CI 0.77-0.82, p < .001) and 0.75 for intensity (95% CI 0.71-0.78, p = .012). Individuals reporting high levels of exercise frequency, intensity, and a combination of the two showed a smaller proportion of adverse health markers than those reporting no regular exercise. Predictive validity assessed by Cox proportional hazards modeling of mortality showed that the high and moderate levels of frequency, intensity, and combined exercise groups differed significantly (all p < .001) from the no exercise group. We have found that these exercise questions, though simple, appear reliable and valid. The finding that even comparatively crude exercise questions can demonstrate an important relationship to death suggests that the signal for exercise is a strong one, and future studies should seek to better examine mechanisms by which exercise benefit is conferred.