Abstract Body (Do not enter title and authors here): Background: There is much debate about whether physical activity (PA) should be maintained in environments with high levels of air pollution. Almost all previously studies on the effect of the interaction between PM_2.5 and physical activity on cardiovascular diseases (CVD) used self-reported physical activity data, which are prone to overestimation and less accurate than objective measures.
Research Questions: whether physical activity should still be encouraged in high air pollution environments.
Aims: To evaluate the association between PA and CVD mortality at different level of PM_2.5.
Methods: We included 77,877 participants with available accelerometer-derived PA data from the UK Biobank prospective cohort study. Machine learning model was used to calculate weekly moderate-to-vigorous physical activity (MVPA) time. UK’s Department for Environment, Food and Rural Affairs (DEFRA)-sourced PM_2.5 information was matched against participant home location information. Mean annual PM_2.5 concentrations were calculated for each participant between 2010 and 2022 (before the endpoint event). Endpoints were defined as CVD mortality and deaths from CVD subtypes such as acute myocardial infarction.
Results: There was a significant negative correlation between MVPA and risk of CVD mortality, but MVPA beyond 400 min could not further decrease the risk of CVD mortality (aHR: 0.91, 95%CI: 0.82, 1.02). When the weekly MVPA time was between 0 and 300 minutes, the association of PM_2.5 with CVD death decreased rapidly with increasing MVPA time. When weekly MVPA time exceeded 300 minutes, further increases in MVPA time instead enhanced the cardiovascular harms of air pollution. Correspondingly, there was a significant difference in the effect of MVPA on mortality between high and low PM_2.5 levels. In participants with long-term exposure to higher levels of PM_2.5 (>10μg/m³), MVPA showed a U-shaped relationship with the risk of acute myocardial infarction (AMI) mortality, and further increases in MVPA beyond 400 minutes per week significantly increased the risk of AMI mortality (aHR per 100 minutes increment: 1.29, 95%CI: 1.10, 1.50).
Conclusions: This study, using accelerometer-sourced PA data, found that MVPA for more than 400 minutes per week had limited benefit for all-cause mortality and was significantly associated with higher AMI mortality in individuals with long-term exposure to high PM_2.5 (>10μg/m³).