- Air pollution increases the risk of developing high blood pressure, especially in non-exercisers
- For every increase in fine particulate matter or PM2.5 level, the risk of hypertension rises by 38%
- High physical activity and exposure to lower levels of pollution, reduce the risk of high blood pressure
Regular exercise lowers the risk of high blood pressure, even if people reside in areas where levels of air pollution is high. Air pollution increases the risk of cardiovascular diseases including, hypertension. Lack of physical activity is also a key contributor towards heart diseases.
In 2004, the American Heart Association issued a scientific statement concluding exposure to air pollution contributes to cardiovascular illness like heart attack, stroke, arrhythmia, heart failure, and death.
Air pollution is assessed by exposure to fine particulate matter (PM2.5). The risk-benefit relationship between air pollution and physical activity is an important public concern because more than 91% of people worldwide live in areas where air quality does not meet World Health Organization (WHO) guidelines.
The findings are published in the American Heart Association's flagship journal Circulation.
"Extended outdoor activity in urban areas increases the intake of air pollutants, which can worsen the harmful health effects of air pollution," said study author Xiang Qian Lao, Ph.D., an associate professor at the Jockey Club School of Public Health and Primary Care at The Chinese University of Hong Kong in Shatin, Hong Kong. "While we found that high physical activity combined with lower air pollution exposure was linked to lower risk of high blood pressure, physical activity continued to have a protective effect even when people were exposed to high pollution levels. The message is that physical activity, even in polluted air, is an important high blood pressure prevention strategy."
For the study, 140,000 individuals from Taiwan who had no hypertension, were recruited. The participants were followed for a period of 5 years.
The weekly levels of physical activity were classified as inactive, moderately active, or highly active. The level of exposure to fine particulate matter (PM2.5) was classified as low, moderate, and high. High blood pressure was defined as 140/90 mm Hg.
The results showed that high physical activity and exposure to lower levels of pollution, reduced the risk of high blood pressure. On the other hand, Inactivity combined with exposure to high levels of pollution raised the risk of high B.P in participants.
For every increase in PM2.5 level, the risk of hypertension rose by 38%. Increase in physical activity level reduced the risk of hypertension by 6%.
The findings suggest that reducing air pollution effectively prevents high blood pressure.
The benefits of regular physical activity on reducing blood pressure are regardless of pollution levels. People who exercise moderately have a 4% lower risk of high blood pressure, compared to those who did not exercise.
People who exercise at intensely, have a 13% lower risk of high blood pressure than the non-exercisers.
The findings were only among the people of Taiwan where ambient air was moderately polluted (the annual PM2.5 concentration was 2.6 times of the limit recommended by the World Health Organization), and hence cannot be generalized.
Researchers included cigarette smoking as a variable. The study did not distinguish between outdoor and indoor physical activity, meaning they could not exclusively examine the association of PM2.5 and hypertension relative to physical activity outdoors or indoors.
"This is the largest study to analyze the combined effects of air pollution and regular physical activity on high blood pressure. Our findings indicate that regular physical activity is a safe approach for people living in relatively polluted regions to prevent high blood pressure. Exercise should be promoted even in polluted areas. The findings also put a spotlight on how strongly pollution can impact blood pressure, and how important it is to control pollution levels to prevent high blood pressure," Lao said.
Writing group author Russell V. Luepker, M.D., M.S., a volunteer expert for the American Heart Association said, "This study confirms our understanding of the role of physical activity in the prevention of cardiovascular diseases including hypertension. It also reminds us of the importance of air pollution in the development of cardiovascular diseases. The link between pollution and cardiovascular disease may include the development of hypertension along with other factors associated with particulate matter in air pollution."