People who exercised in areas with high levels of traffic-related air pollution were not more likely to suffer incident or recurrent myocardial infarction (MI) than people exercising in areas with lower levels of pollution, according to the results of a study published in the Journal of the American Heart Association.
Physical activity levels of 57,053 participants in the Danish Diet, Cancer, and Health cohort were recorded at baseline, and nitrogen dioxide levels were estimated at their residencies. The likelihood of the primary outcome — incident or recurrent MIs — was compared between participants according to their estimated nitrogen dioxide levels.
Of the 57,053 participants, 50,635 had not had a previous MI at baseline. During follow-up, 2936 participants developed incident MI. Of the 1233 participants who had an MI before the study, 324 had recurring MI during follow-up. In the total cohort, the mean concentration of nitrogen dioxide was 18.7 μg/m3 vs 18.9 μg/m3 in participants who developed an incident or recurrent MI during follow-up. All physical activities (sports, cycling, and gardening) except walking were associated with a significant decreased risk (9%-15%) for MI.
Additionally, individuals living in areas with high nitrogen dioxide levels had a higher risk for incident MI; however, in the primary study outcome, people living in areas with higher levels of nitrogen dioxide saw no statistically significant association between incident or recurrent MI with participation in physical activities.
The study authors wrote, “[T]he risk of MI increased with increasing levels of [nitrogen dioxide], in participants who were not physically active, while the benefits of physical activity remained in all 3 [nitrogen dioxide] level groups.”
They added, “[W]e can conclude that the long-term benefits of physical activity in preventing the development of MI in healthy, middle-aged participants, and possibly as effective disease control in patients with prior MI, can outweigh the risks associated with enhanced residential exposure to traffic-related air pollution during physical activity.”
Kubesch N, Jørgensen J, Hoffmann B, et al. Effects of leisure-time and transport-related physical activities on the risk of incident and recurrent myocardial infarction and interaction with traffic-related air pollution: a cohort study [published online July 18, 2018]. J Am Heart Assoc. doi:10.1161/JAHA.118.009554