The effect of physical activity and cardiorespiratory fitness on all-cause mortality in Hong Kong Chinese older adults

Background: It is unclear whether physical activity (PA) could predict all-cause mortality independently of cardiorespiratory fitness, and there are relatively few studies evaluating the combined effect of PA and cardiorespiratory fitness on mortality. Methods: We invited 1,242 Chinese older adults aged 69-94 years from the MrOs and MsOs cohort (Hong Kong) study for a 7-year followup. PA was measured by the Physical Activity Scale of the Elderly (PASE). Cardiorespiratory fitness, expressed as maximal oxygen uptake (VO2max), was assessed by performing symptom-limited maximal exercise testing on an electrically braked bicycle ergometer and 6-m walk test. We aimed to examine the independent and combined effect of PA and VO2max with all-cause mortality by cox proportional hazards models. Results: Ninety-nine deaths occurred over a mean follow-up of 5.3 } 0.8 years. PA was inversely associated with all-cause mortality in unadjusted and fully-adjusted models, and the association was still significant after further adjusted for VO2max. In stratified analysis, PA was significantly related to all-cause mortality within both unfit and fit strata. As compared with those being active and fit, physically inactive and cardiorespiratory unfit individuals had the highest all-cause mortality risk. Physically active but unfit individuals and inactive but fit individuals had similar all-cause mortality risk. Conclusions: Among older adults, PA was an important predictor of all-cause mortality independently of VO2max. High cardiorespiratory fitness does not necessarily confer low mortality risk in physically inactive older adults.