In Denmark’s large cities, the benefits of exercise were found to far outweigh potential risks from exposure to air pollution in a study that explored air quality and heart attack risk. Results were recently published in the Journal of the American Heart Association and highlight the importance of physical activity for the prevention of heart disease.
This study included more than 57,000 middle-aged adults from the Danish Diet, Cancer and Health study, which explores the impact of diet and lifestyle on health outcomes. Participants were from the two largest cities in Denmark—Copenhagen and Aarhus—where air pollution is a concern.
Upon enrolling between 1993 and 1997, participants completed a detailed questionnaire about their health, including their current level of physical activity. The questionnaire covered activities like sports, biking, walking, and gardening—most of which are done outside. Researchers then used air quality records to estimate their exposure to air pollution during their enrollment year.
After following participants through 2015, 6% of healthy adults experienced their first heart attack, and 26% of those with a history of heart attack experienced a second heart event during follow-up. Analysis showed that exposure to air pollution significantly increased risk for heart attack. However, this exposure didn’t negate the benefits of outdoor exercise.
In both groups, researchers found that activities like sports, biking, walking and gardening were associated with lower risk of heart attack. Among healthy adults, sports, biking and gardening was associated with a 9–15% reduction in heart attack risk. Among those with existing heart disease, biking, walking and gardening were associated with up to 20% lower risk for a second heart attack than those who didn’t exercise, although these associations were not considered significant.
After taking into account exposure to air pollution during these activities, poor air quality had no impact on the association between exercise and heart attack risk.
The take-home message, according to authors, is that the long-term benefits of exercise outweigh concerns about air pollution. It’s well established that physical activity significantly reduces risk for heart disease and heart events. While air pollution has been linked to increased heart risks, these concerns shouldn’t discourage individuals from getting outside and exercising.
However, it’s also important to note that this study was conducted in Denmark, where air pollution is not as high as other large cities like those in China and India. The study also used average air quality records to estimate exposure to air pollution, which isn’t as precise as measuring air quality during exercise. Therefore, additional research is needed to better understand the issue and help generalize findings to other cities.