Residential greenness and increased physical activity in patients after coronary artery bypass graft surgery

Aims: Physical activity is a fundamental component of rehabilitation following coronary artery bypass (CABG) surgery. Proximity to neighbourhood green spaces may encourage physical activity. We investigated the association between residential greenness and exercise-related physical activity post-CABG surgery. Methods: Participants in a prospective cohort study of 846 patients (78% men) who underwent CABG surgery at seven cardiothoracic units during the time period 2004-2007 were interviewed regarding their physical activity habits one day before and one year after surgery. Exposure to residential neighbourhood greenness (within a 300 m buffer around their place of residence) was measured using the Normalized Difference Vegetative Index. Participation in exercise-related physical activity (yes/no), weekly duration of exercise-related physical activity and the change in exercise-related physical activity between baseline and follow-up were examined for associations with residential greenness, adjusting for socio-demographic factors, propensity score adjusted participation in cardiac rehabilitation and health-related covariates after multiple imputation for missing variables. Results: Living in a higher quartile of residential greenness was associated with a 52% greater odds of being physically active (OR 1.52, 95% CI 1.22-1.90). This association persisted only (OR 1.75, 95% CI 1.35-2.27) among patients who did not participate in cardiac rehabilitation following surgery and was stronger in women (OR 2.38, 95% CI 1.40-4.07) than in men (OR 1.37, 95% CI 1.07-1.75). Participants who lived in greener areas were more likely to increase their post-surgical physical activity than those who lived in less green areas (OR 1.59, 95% CI 1.25-2.01). Conclusions: Residential greenness appears to be beneficial in increasing exercise-related physical activity in cardiac patients, especially those not particpating in cardiac rehabilitation after CABG surgery.