Physical functioning and mortality in older women: an assessment of energy costs and level of difficulty

We tested the hypothesis that the types of activity and the energy equivalent assigned to each activity affect the relationship between self-reported physical functioning and mortality.

We analyzed the relationship between physical functioning and cardiovascular and noncardiovascular mortality in 1230 women (median age 70 years) observed for 7.5 years. We evaluated five separate scores of physical functioning that differed in the method of scoring the responses. Cox proportional hazard models included baseline age, self-reported physical functioning, medical morbidity, and assessment of health.

For cardiac and noncardiovascular mortality, greater self-reported functioning was associated independently with a decreased hazard of death. The effects of physical functioning were sensitive to the form of the score used; that is, a score based on ordinal responses was associated with a greater reduction in hazard of death difference in survival between high and low function score: Ordinal: -15.2% (95% confidence interval [CI] -25.2--4.0); dichotomous: -11.6% (95%CI -18.9--3.9).

There is a consistent relationship between functional limitation and all causes of mortality. The association is sensitive to the form of the score. Future physical function scores should be based on ordinal responses to individual items used in the scores.