Background To investigate the dose-response association between physical activity and lower respiratory tract infection (LoRI) outcomes in patients with cardiovascular disease. Methods and Results Using the Korean National Health Insurance data, we identified individuals aged 18 to 99 years (mean age, 62.6±11.3 years; women, 49.6%) with cardiovascular disease who participated in health screening from January 1, 2009, to December 31, 2012 (n=1 048 502), and were followed up until 2018 for mortality and until 2019 for hospitalization. Amount of physical activity was assessed using self-reported questionnaires and categorized into 5 groups: 0 (completely sedentary), <500, 500 to 999, 1000 to 1499, and ≥1500 metabolic equivalents of task min/wk. After controlling for various confounders, adjusted hazard ratios (95% CIs) were 1.00 (reference), 0.74 (0.70-0.78), 0.66 (0.62-0.70), 0.52 (0.47-0.57), and 0.54 (0.49-0.60) for LoRI mortality, and 1.00 (reference), 0.84 (0.83-0.85), 0.77 (0.76-0.79), 0.72 (0.70-0.73), and 0.71 (0.69-0.73) for LoRI hospitalization among those engaging in physical activity of 0, <500, 500 to 999, 1000 to 1499, and ≥1500 metabolic equivalents of task min/wk, respectively. Assuming linear association between 0 and 2000 metabolic equivalents of task min/wk, each 500-metabolic equivalents of task min/wk increase of physical activity was associated with reduced LoRI mortality and hospitalization by 22% and 13%, respectively. The negative association was stronger in the older population than in the younger population (P for interaction <0.01). Conclusions In patients with cardiovascular disease, engaging in even a low level of physical activity was associated with a decreased risk of mortality and hospitalization from LoRI than being completely sedentary, and incremental risk reduction was observed with increased physical activity.
Keywords: cardiovascular disease; dose‐response; physical activity; respiratory tract infection.