Abstract P298: Associations Between Time-varying Physical Activity and Physical Performance Measures in Postmenopausal Women: the Women’s Health Initiative

Abstract

Introduction: Maintaining regular physical activity (PA) may delay the onset of functional disability and preserve mobility later in life. Whereas many population-based studies have reported the prospective relationship of initial PA levels to later-life functional status, few studies have examined the longitudinal relationships between changes in PA to changes in physical functioning. This study examined associations between changes in PA and changes in standard physical performance measures (PPM) over 6-years in older women. Methods: Recreational PA was reported using the WHI questionnaire; gait speed, timed chair stand, and grip strength were assessed in clinic using standardized protocols. Exposures were assessed at baseline, years 1, 3 and 6 of the Women’s Health Initiative Clinical Trials (n=5092 women; mean age = 69.8 y). Mixed effects linear regression models were used to evaluate the association between time-varying PA and change in each PPM. Potential interactions between time-varying PA and race and age (<70 y; ≥70 y) were also tested. Results: At baseline, 23.0% women were categorized as sedentary (SED; <100 MET-min/wk), 30.4% as light PA level (100- <500 MET-min/wk), 27.5% as moderate (500- <1200 MET-min/wk); and 19.1% as high PA (≥ 1200 MET-min/wk). Significant, dose-response associations between PA and improvements in all PPMs were observed over the 6 y follow-up after adjusting for demographic, lifestyle, and clinical factors. Compared to SED, women in the high PA groups showed better grip strength (0.48 kg higher; P <0.01), more chair stands (0.35 more; P <0.001), and faster gait speeds (0.06 m/s faster ; P <0.001). Older women (≥70 y) benefited more from higher levels of PA than the younger women (P interaction for age =0.014), as reflected by their greater increase in chair stands ( P <0.001); however, interactions between PA and race were not significant. Conclusions: These findings provide evidence that, in post-menopausal women, maintaining higher PA levels over time is associated with benefits in lower extremity function, as compared to being sedentary. These data are consistent with the view that regular PA plays an important role in maintaining functional status during aging, particularly in older women.