Interaction of physical activity and low-level air pollution on cardiovascular disease: a prospective cohort study in UK Biobank

To investigate the associations of physical activity (PA), low-level air pollution, and interaction on cardiovascular diseases (CVD) incidence based on the UK Biobank. PA was measured by the International Physical Activity Questionnaire and five air pollutants were estimated using Land Use Regression. All association estimates were based on Cox regression. Dose–response relationship was explored by restricted cubic spline, while multiplicative and additive interaction were examined by P interaction and relative excess risk due to interaction (RERI). As deviating proportional hazards assumption, we analyzed data as follow-up