Association of Objectively Measured Physical Activity With Cardiovascular Risk in Mobility‐limited Older Adults

BACKGROUND: Data are sparse regarding the impacts of habitual physical activity (PA) and sedentary behavior on cardiovascular (CV) risk in older adults with mobility limitations. METHODS AND RESULTS: This study examined the baseline, cross‐sectional association between CV risk and objectively measured PA among participants in the Lifestyle Interventions and Independence for Elders (LIFE) study. The relationship between accelerometry measures and predicted 10‐year Hard Coronary Heart Disease (HCHD) risk was modeled by using linear regression, stratified according to CVD history. Participants (n=1170, 79±5 years) spent 642±111 min/day in sedentary behavior (ie, <100 accelerometry counts/min). They also spent 138±43 min/day engaging in PA registering 100 to 499 accelerometry counts/min and 54±37 min/day engaging in PA ≥500 counts/min. Each minute per day spent being sedentary was associated with increased HCHD risk among both those with (0.04%, 95% CI 0.02% to 0.05%) and those without (0.03%, 95% CI 0.02% to 0.03%) CVD. The time spent engaging in activities 100 to 499 as well as ≥500 counts/min was associated with decreased risk among both those with and without CVD (P<0.05). The mean number of counts per minute of daily PA was not significantly associated with HCHD risk in any model (P>0.05). However, a significant interaction was observed between sex and count frequency (P=0.036) for those without CVD, as counts per minute was related to HCHD risk in women (β=−0.94, −1.48 to −0.41; P<0.001) but not in men (β=−0.14, −0.59 to 0.88; P=0.704). CONCLUSIONS: Daily time spent being sedentary is positively associated with predicted 10‐year HCHD risk among mobility‐limited older adults. Duration, but not intensity (ie, mean counts/min), of daily PA is inversely associated with HCHD risk score in this population—although the association for intensity may be sex specific among persons without CVD. CLINICAL TRIAL REGISTRATION: URL: www.clinicaltrials.gov Unique identifier: NCT01072500