Independent and joint associations of sedentary behaviour and physical activity with risk of recurrent cardiovascular events in 40,156 Australian adults with coronary heart disease

Objective: Explore the independent and joint associations between sedentary behaviour and physical activity with cardiovascular events, among individuals with coronary heart disease (CHD). Methods: Cohort study including Australians ≥45 years with CHD (2006-2020). Time in sedentary behaviour, walking, moderate-, and vigorous- physical activity were self-reported. Cardiovascular events were identified using health registers (2006-2022). Cox proportional hazard regressions explored the association. Restricted cubic splines explored the shape of the association. Results: There were 40,156 individuals included, with a mean age of 70 (SD=10) years old, 62 % men. During a median of 8.3 (IQR = 10.03) years, 3260 non-fatal-, 5161 total cardiac events, and 14,383 major adverse cardiovascular events (MACE) were recorded. Sedentary behaviour of 7-10.4 h/day was associated with a 15 % lower risk of total cardiac events and MACE compared to ≥ 10.5 h/day. A higher level of moderate-to-vigorous physical activity was associated with a lower risk of cardiovascular events, with 14-21 % lower risk for 1-149 min/week compared to 0 min/week. A similar pattern was seen for walking and activities at a moderate- or vigorous intensity. The joint association of ≥150 min/week of moderate-to-vigorous physical activity and <7 h/day in sedentary behaviour had the lowest risk (29-48 % lower) for cardiovascular events compared to the reference group. However, moderate-to-vigorous physical activity seems to be of greater importance and partly modifies the risk of sedentary behaviour in the joint association. Sedentary behaviour hours were linearly associated with risks of non-fatal and total cardiac events. Meanwhile time in physical activity had a curvilinear association with cardiovascular events, with the greatest benefits at the beginning of the curve. Conclusion: More time in physical activity and less time in sedentary behaviour are associated with a lower risk of cardiovascular events. This emphasizes the importance of providing recommendations for both physical activity and sedentary behaviour to people with CHD.