Health gains from regular physical activity outweigh harmful effects of air pollution

30 Sep 2019 bởiJairia Dela Cruz
Health gains from regular physical activity outweigh harmful effects of air pollution

Regular physical activity (PA) confers benefits for mortality, and its beneficial effects prevail over the deleterious consequences of long-term exposure to air pollution, as reported in a recent study from Hong Kong.  

“Due to an increased ventilation rate, the uptake of air pollution during PA increases considerably, potentially intensifying the detrimental health effects of air pollution,” researchers noted.

However, the researchers found little evidence to suggest interaction between habitual PA (volume and type) and long-term exposure to fine particulate matter (PM2.5), saying that the findings support the promotion of PA for disease prevention even in individuals residing in relatively more polluted areas.

The analysis included 58,643 participants (mean age, 71.9 years; 65.7 percent female) from the Elderly Health Service Cohort. Most of these participants (n=47,453; 80.9 percent) engaged in low-to-moderate PA (1.0–20.9 MET-hours/week). The most common type of activity performed was stretching exercise (38.1 percent), followed by walking slowly (18.4 percent), traditional Chinese exercise (17.8 percent) and aerobic exercise (10.0 percent).

Participants who engaged in a higher vs lower (<1.0 MET-hours/week) volume of PA had lower mortality risk. The corresponding hazard ratios associated with low-to-moderate (1.0–20.9 MET-hours/week) and high (21 MET-hours/week) PA were 0.91 (95 percent CI, 0.88–0.95) and 0.75 (0.68–0.83). Aerobic exercises, including jogging and cycling and traditional Chinese exercise such as Tai Chi, exerted more pronounced effects. [Int J Epidemiol 2019;doi:10.1093/ije/dyz184]

Meanwhile, participants residing in high- vs low-polluted areas (<35.3 vs ≥35.3 µg/m3) were at greater risk of dying from cardiovascular causes. Every 10-µg/m3 increase in PM2.5 concentration carried a 19-percent increase in cardiovascular mortality (HR, 1.19, 1.05–1.35), as well as a 2-percent increase in respiratory mortality (HR, 1.02, 0.87–1.19).

When the combined effects of PA volume and air pollution exposure were examined, the HRs for the risk of cardiovascular disease associated with performing a low volume of PA in low- or high-PM2.5 areas were 1.46 (1.11–1.92) and 1.53 (1.17–2.00), respectively, as compared with performing high PA volume in low-polluted areas (p-interaction=0.77). The corresponding HRs for respiratory disease were 1.31 (0.95–1.82) and 1.50 (1.09–2.06; p-interaction=0.16). There was no additive or multiplicative interaction between PA and long-term exposure to PM2.5.

“Our findings add to the scarce evidence of the risk–benefit relationship between long-term health benefits of habitual PA and air pollution,” as well as provide a more comprehensive picture of the combined effects of the two exposures, given that the analyses were conducted in Hong Kong, which is ranked among the 20 percent of most polluted cities globally, the researchers pointed out.

“[T]he additional inhaled air pollutants due to PA only account for a small fraction of the total inhaled air pollutants,” they said, explaining the general protective effects of PA on mortality regardless of PM2.5 concentration levels.

Additionally, it is not unlikely that the long-term health benefits of habitual PA may reverse the acute adverse mortality effects associated with exposure to higher levels of air pollution during PA, the researchers noted.

More studies in higher air pollution areas or among a younger population are warranted to confirm or refute the study’s findings, they added.