Physical Exercise Could Mitigate Effects of Pollution on Hypertension Risk

Xiang Qian Lao, PhD

New research suggests regular physical activity could help mitigate the negative cardiovascular effects of living in heavily polluted areas.

Following nearly 150,000 patients for half a decade, investigators found regular exercise aids in the management of blood pressure even among patients living in areas with increased levels of fine particulate matter (PM2.5).

“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,” said lead investigator Xiang Qian Lao, PhD, an associate professor at the Jockey Club School of Public Health and Primary Care at the Chinese University of Hong Kong, in a statement. “The message is that physical activity, even in polluted air, is an important high blood pressure prevention strategy.”

With pollution levels a major concern in many parts of the world and the risk-benefit relationship between physical activity and exposure to excess levels of pollution is now a point of discussion. Despite the obvious benefits of physical activity, some have purported the amount of pollution in an area could mitigate those benefits.

To address this topic, Lao and a team of colleagues from organizations across China designed a study to examine joint associations of physical activity and long-term exposure to PM2.5 with the development of hypertension in a longitudinal cohort of Taiwanese patients. Using data from the MJ Health Management Institution, which has provided medical screenings to Taiwan citizens since 1994, investigators identified a cohort of 140,072 for inclusion in their study.

The mean age of patients inured was 41.7 years, 48.8% were male, mean exposure of PM2.5 was 26.1±7.3 μg/m3, the mean systolic blood pressure was 112.5 mmHg, and the mean diastolic blood pressure was 68.7 mmHg. In regard to physical activity, 34.2% were considered inactive, 29.8% had moderate activity, and 36.0% had a high level of physical activity.

For inclusion in the study, patients need to be at least 18 years of age, have data related to blood pressure readings between 2001-2016, and be free of hypertension at baseline. From the 140,072 adult patients included, investigators obtained data from 360,095 medical records between 2001-2016.

Exposure to PM2.5 was determined through a spatiotemporal model at a resolution of 1x1 km2 using aerosol optical depth data. These measures were validated using data from 70 ground-level air pollution monitoring stations across Taiwan. Physical activity among participants was classified as inactive (Metabolic equivalent hours [MET-h]=0), moderate physical activity (MET-h=0-8.75), and high physical activity (more than 8.75 MET-h).

Of note, age, sex, education levels, BMI, physical activity at work, cigarette smoking status, vegetable and fruit intake, diabetes status, dyslipidemia, cardiovascular disease, baseline systolic blood pressure, and month of enrollment were all included in as covariates in the current study.

Upon adjustment for covariates, results indicated higher physical activity levels were associated with a lower risk of hypertension compared to those considered inactive (moderate: HR, 0.93; 95% CI, 0.89-0.97; high: HR, 0.92; 95% CI, 0.88-0.96). Conversely, results indicated higher levels of PM2.5 were associated with a greater risk of hypertension (moderate-PM2.5: HR, 1.37; 95% CI, 1.32-1.43; high: HR, 1.92; 95% CI, 1.81-2.04). No significant interactions were noted between physical activity and PM2.5 (HR, 1.01; 95% CI, 1.00-1.02).

“This is the largest study to analyze the combined effects of air pollution and regular physical activity on high blood pressure,” Lao added. “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.”

This study, “Independent and Opposing Associations of Habitual Exercise and Chronic PM2.5 Exposures on Hypertension Incidence,” was published in Circulation.