Replacing sedentary time with physical activity may lower risk of all-cause mortality

1. In this prospective cohort, individuals with greater periods of sedentary time have increased risks of all-cause mortality and mortality from cancer, cardiovascular disease, and respiratory disease. 

2. Replacing sedentary behaviour with physical activity substantially lowers these risks. 

Evidence Rating Level: 1 (Excellent) 

Sedentary behaviour (SB), defined as low-energy acivities have become increasingly common and is strongly associated with a higher risk of chronic disease and premature death. Previous studies have shown that sitting more than 6-8 hours per day raises all‑cause and cardiovascular mortality, while greater physical activity can offset part of this risk. Also suggested was that swapping sedentary time for moderate‑to‑vigorous activity lowers risks of sarcopenia and mortality, but far less is known about which specific, everyday activities offer the greatest benefit. This study examined how sedentary time relates to all-cause and cause‑specific mortality and to identify which types of physical activity most effectively reduce these risks. The cohort included eligible individuals from the UK Biobank and the National Health and Nutrition Examination Survey (NHANES). Sedentary time was assessed through participant surveys, providing an average amount of hours they spent each week watching TV, using a computer, or driving. During the follow-up period, more time spent sitting daily was associated with higher risks of all-cause mortality, as well as mortality from cancer, cardiovascular disease, and respiratory disease, compared with sitting less than 5 hours per day. In the UK Biobank, 36,109 deaths occurred over 13.5 years, while in NHANES, 3,057 deaths occurred over 6.7 years. Replacing sedentary time with physical activity lowered all-cause mortality risk by 3.5% (hazard ratio [HR] 0.965, 95% CI 0.954-0.977). Cause‑specific mortality also fell: 1.6% for cancer (HR 0.984, 95% CI 0.968–1.000), 4.4% for cardiovascular disease (HR 0.956, 95% CI 0.930–0.982), and 15.5% for respiratory disease (HR 0.845, 95% CI 0.795–0.899). The benefits increased with more intense activity or longer replacement periods. These findings indicate that prolonged SBis significantly associated with higher all-cause and cause-specific mortality, and even modest everyday physical activity can meaningfully counteract this. 

Click here to read this study in BMC Medicine

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