Does Physical Activity or Sedentary Behavior Moderate the Association of Smoking Consumption With All-Cause and Cardiovascular Disease Mortality?

BACKGROUND: Smoking is the most significant risk factor for major diseases, including cancer, respiratory diseases, and cardiovascular diseases (CVD). Extensive studies have identified physical activity (PA) and sedentary behavior (SB) as modifiable lifestyle factors that provide substantial health benefits. This study aimed to assess the effects of PA and SB on smoking-related mortality. METHODS: This study included 8542 adults from the 2014-2015 Korea National Health and Nutrition Examination Survey, with mortality follow-up data tracked through 2019. PA, SB, and smoking status were assessed using self-reported questionnaires. Cox regression was used to estimate the individual and combined effects of smoking status, PA, and SB on all-cause and CVD-related mortality. The interactions were assessed using a multiplicative scale. RESULTS: As of December 31, 2019, a total of 147 participants had died from all causes, including 32 deaths attributed to CVD. Both smokers (all-cause: 0.49 [0.32-0.76], CVD: 0.22 [0.06-0.76]) and nonsmokers (all-cause: 0.38 [0.21-0.68], CVD: 0.18 [0.05-0.64]) who adhered to PA guidelines exhibited significant reductions in mortality rates. Similarly, limiting daily sedentary time to <8 hours reduced mortality rates in both smokers and nonsmokers, with more pronounced effects in nonsmokers (all-cause: 0.34 [0.19-0.61], CVD: 0.12 [0.03-0.45]). Even without adhering to the sedentary guidelines, each additional hour of reduced sedentary time significantly lowered mortality rates among smokers (all-cause: P < .0001, CVD: P = .0064). CONCLUSIONS: This study highlighted that PA and SB can attenuate the association between smoking and mortality, including all-cause and CVD-related mortality. For optimal health promotion, practicing smoking cessation, engaging in PA, and reducing SB are recommended simultaneously.