Although studies have shown that exercise in older men decreases the risk of cardiovascular disease and all-cause mortality, only one study examined the effect of physical activity on older women, and no mortality benefit was found. Gregg and colleagues conducted a study of community-dwelling older women to determine whether exercise influences mortality in this population.
Participants in the Study of Osteoporotic Fractures served as the study sample, with baseline and follow-up data on physical activity. Physical activity was assessed by questionnaire and categorized according to activity at baseline and at follow-up, yielding four groups: those sedentary at baseline and follow-up, those active at baseline who became sedentary, those who were sedentary and became active, and those who were physically active at baseline and follow-up.
In the analysis, 7,553 participants in the effects of change in physical activity study were followed over 6.7 years, with 1,029 deaths. Higher levels of total physical activity and walking at baseline were associated with lower all-cause and cardiovascular disease mortality rates. Compared with always-sedentary women, sedentary women who became active had significantly reduced all-cause mortality rates, with hazard rate ratios increasing in the middle and later years of the study. Cardiovascular disease mortality tended to be lowest in women with the greatest increases in physical activity. Women who were always active had significant reductions of mortality related to all causes and cardiovascular disease. Women who became sedentary had similar mortality rates to those who were always sedentary. Although the association between physical activity changes were similar regardless of risk status, when the first two years of follow-up were excluded, the mortality benefit of physical activity was attenuated in the highest risk women. Exclusion of the first two years of follow-up also attenuated apparent benefit in women younger than 75 years.
Recent physical activity was a more reliable predictor of longevity than past activity, with women who became active having similar mortality rates to those who were always active, and those who became sedentary similar to those who were always sedentary. The authors speculate that cardiovascular disease risk factor reduction, reduced fall risk, improved cardiorespiratory fitness, among other factors, could contribute to improved mortality. The improvements appear to be greatest among women younger than 75 years. Selection bias, confounding, and other limitations leading to overestimation of effect could account for the authors' secondary analysis of data from a cohort study. While these data suggest that modest increases in physical activity could have a large mortality benefit in the aging population, randomized controlled trials are needed to rule out the influence of self-selection factors.