Physical Activity and Sedentary Behaviour Thresholds for Secondary Prevention of Coronary Heart Disease: Morbidity Survival Tree Analysis

Background: There are no diagnosis-specific guidelines for moderate-to-vigorous physical activity (MVPA) and sedentary behaviour (SB) for coronary heart disease (CHD). This study aimed to identify thresholds of MVPA and SB associated with cardiovascular events. Methods: This cohort study included individuals with CHD. MVPA and SB were self-reported, and health registries identified cardiovascular events in the years 2006-2022. Survival tree analyses identified thresholds of time associated with the risk of cardiovascular events. Thresholds were explored with the use of Cox regression models. Results: There were 40,156 Australians, mean age 70 years, 62% men. Over a median 8.3 years, 3260 nonfatal cardiac events, 5161 total cardiac events, and 14,383 major adverse cardiovascular events (MACE) occurred. Thresholds for MVPA were 122 min/wk for nonfatal cardiac events and 94 min/wk for total cardiac events and MACE. Meeting MVPA thresholds was associated with an 18% lower risk for nonfatal cardiac events, 29% lower risk of total cardiac events, and 23% lower risk of MACE than not reaching the thresholds. Thresholds for SB were 4 and 10 h/d, respectively, for risk of total cardiac events and MACE. SB below thresholds was associated with a 14% lower risk of total cardiac events and an 18% lower risk of MACE. There were sex-specific thresholds for MVPA and SB. Conclusions: To lower cardiovascular event risk, identified MVPA thresholds were lower (94-122 min/wk) than the public health guidelines (150 min/wk) in individuals with CHD. The SB thresholds associated with a lower risk of total cardiac events and MACE varied from 4 to 10 h/d.