Exercise counteracts a dangerous effect of air pollution

Ninety-one percent of the world's population deals with an often invisible, insidious health threat every time they step outside: air pollution.

Dirty, smoky, toxic air takes a toll on well being over time, contributing to mental health disorders, respiratory diseases, and early death. Some researchers recently linked poor quality air to more severe cases of Covid-19.

Even when it's not clearly visible, bad air can sneak its way into our lungs and cause harm. In a recent study, researchers uncover one strategy that can counteract some of these dangerous effects, no matter where you live: exercise.

The study, the largest to date exploring how physical activity, high blood pressure, and air pollution relate, shows being active can reduce one's risk of hypertension regardless of air pollution levels.

Hypertension — when blood pressure runs high for too long — can damage the heart and lead to strokes and heart attacks. In 2016, high blood pressure contributed to 31.6 percent of the world's total number of deaths.

“Extended outdoor activity in urban areas increases the intake of air pollutants, which can worsen the harmful health effects of air pollution,” study co-author Xiang Qian Lao, a researcher at The Chinese University of Hong Kong, explains.

When you work out — it could be biking, running, or whatever suits you — you breathe more heavily. This potentially accelerates the levels of air pollution consumed. Physical activity outweighs this potentially heightened risk, at least when it comes to high blood pressure, the study suggests.

The research team found that high physical activity and lower air pollution exposure were linked to lower risk of high blood pressure. Meanwhile, low activity and high air pollution spiked risk of high blood pressure.

Surprisingly, 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," Lao said. The team's findings were published Monday in the journal Circulation.

Breathe in, breathe out — To better understand how the air we breathe and our level of physical activity influence hypertension, researchers studied more than 140,000 adults without high blood pressure in Taiwan. The team followed them for an average of 5 years, tracking their activity levels and whether they developed hypertension over time. High blood pressure was defined as 140/90 millimeters of mercury, a measurement of pressure.

The team then looked at the two-year average of fine particulate matter (PM_2.5) in the air where participants lived using satellite data. PM_2.5 is the most commonly used indicator of air pollution. For participants in the study, the average air pollution concentration was moderately high — approximately 2.6 times the PM_2.5 limit recommended by WHO guidelines.

How does air pollution impact heart health? — Overall, people who were highly active and exposed to low levels of pollution had a lower risk of developing high blood pressure. People who were inactive and exposed to highly polluted air had a higher high blood pressure risk.

The benefits of regular physical activity held up regardless of pollution level: People who exercised moderately had a 4 percent lower risk of high blood pressure than those who didn't exercise. People who exercised at a high level had a 13 percent lower risk of high blood pressure than the non-exercisers.

Highly active people were protected against high blood pressure even when pollution levels were high, suggesting exercise is a modifiable lifestyle factor that can make a meaningful difference.

“Our findings indicate that regular physical activity is a safe approach for people living in relatively polluted regions to prevent high blood pressure," Lao said. "Exercise should be promoted even in polluted areas."

Crucially, the study also found that air pollution was a more powerful factor in driving hypertension risk. Each increase in PM_2.5 level was associated with a 38 percent increase in risk developing hypertension, whereas each increase in physical activity level lead to a 6 percent lower risk of hypertension.

Taken together, the findings suggest that while exercise can help mitigate some of air pollution's dangerous side effects, it can't completely counteract pollution.

To test the robustness of these findings, the study needs to be replicated with communities living in places with far dirtier air. It's possible, as some other studies have found, that the acute health consequences of toxic air can override any benefits from exercise. The team did not distinguish between indoor and outdoor physical activity, so where and how one exercises could also make a difference.

What this research can say is, to keep hearts pumping blood at a healthy rate, it's worth working out on a regular basis.

LONGEVITY HACKS is a regular series from Inverse on the science-backed strategies to live better, healthier, and longer without medicine.

HOW THIS AFFECTS LONGEVITY — Air pollution exposure and lack of physical activity both spike the risk of high blood pressure, a condition that can lead to heart attacks, stroke, and early death.

WHY IT'S A HACK — Exercise can reduce the risk of hypertension, across varying levels of air pollution. Researchers don't know if it can counteract the effects of severely dirty air, but in moderate or low air pollution areas, physical can mitigate any heightened risk of hypertension.

SCIENCE IN ACTION — The study adds to the long list of reasons to break a sweat, no matter where you are. Go for a jog, dance around the room, garden, or lift weights. Just get moving!

HACK SCORE OUT OF 10 — 🕺🏽🕺🏽🕺🏽🕺🏽🕺🏽🕺🏽🕺🏽🕺🏽 (8/10 dance breaks)

Partial Abstract:

Background: We investigated the joint associations of habitual physical activity (PA) and long-term exposure to fine particulate matter (PM2.5) with the development of hypertension in a longitudinal cohort in Taiwan.

Methods: We selected 140,072 adults (18 years of age) without hypertension who joined a standard medical screening program with 360,905 medical examinations between 2001 and 2016. PM2.5 exposure was estimated at each participant’s address using a satellite data-based spatiotemporal model with 1 km2 resolution. Information on habitual PA and a wide range of covariates was collected using a standard self- administered questionnaire. We used the Cox regression model with time- dependent covariates to examine the joint associations.

Conclusions: A high-PA and low PM2.5 exposure were associated with a lower risk of hypertension. The negative association between PA and hypertension remained stable in people exposed to various levels of PM2.5, and the positive association between PM2.5 and hypertension was not modified by PA. Our results indicated that PA is a suitable hypertension prevention strategy for people residing in relatively polluted regions.