All-cause mortality risk as a function of sedentary behavior, moderate-to-vigorous physical activity and cardiorespiratory fitness

Objective: Emerging work demonstrates individual associations of sedentary behavior, moderate-to-vigorous physical activity (MVPA) and cardiorespiratory fitness (CRF) on mortality risk. Limited research has evaluated all three of these parameters in a model when considering mortality risk, and their potential additive association on mortality risk has not been fully evaluated, which was the purpose of this study. Methods: Data from the 2003-2006 National Health and Nutrition Examination Survey were used (N=2,295 adults 20-85yrs), with follow-up through 2011. Sedentary behavior and MVPA were objectively assessed (accelerometry) with cardiorespiratory estimated from a prediction equation taking into consideration participant demographic, anthropometric and behavioral characteristics. Using the median values, a PACS (Physical Activity Cardiorespiratory Sedentary) score was created that ranged from 0-3, indicating the number of these three positive characteristics. Results: Those with below median sedentary behavior did not have a reduced all-cause mortality risk (HR=0.59; 95% CI: 0.34-1.04; P=0.07), but those with above median MVPA (HR=0.35; 95% CI: 0.15-0.82; P=0.02) and above median CRF did (HR=0.20; 95% CI: 0.09-0.43; P < 0.001). Compared to those with a PACS score of 0, those with a PACS score of 1, 2, and 3, respectively, had a 67% (HR=0.33; 95% CI: 0.17-0.63, P=0.002), 82% (HR=0.12; 95% CI: 0.05-0.30; P < 0.001) and 96% (HR=0.04; 95% CI: 0.02-0.11; P < 0.001) reduced risk of all-cause mortality. Conclusion: Cardiorespiratory fitness and MVPA, but not sedentary behavior, were independently associated with reduced mortality risk. Adults with all three characteristics (below median sedentary and above median MVPA and CRF), however, had the lowest mortality risk.