Health benefits of exercise significantly weakened with fine particulate matter >25 \u03bcg\/m\u00b3<\/p>\n<\/h3>\n
By Lori Solomon HealthDay Reporter<\/b>
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THURSDAY, Dec. 11, 2025 (HealthDay News) — Long-term exposure to polluted air can weaken the health benefits of regular exercise, according to a review published online Nov. 28 in BMC Medicine<\/em>.<\/p>\n Po-Wen Ku, Ph.D., from University College London, and colleagues conducted a systematic literature review to assess whether higher levels of fine particulate matter (PM2.5<\/sub>) reduce the protective effects of leisure-time physical activity (LTPA) on all-cause, cardiovascular, and cancer mortality. <\/p>\n Based on seven cohort studies (1.5 million participants; 115,196 deaths), the researchers found that the reduction in all-cause mortality risk diminished with higher PM2.5 <\/sub>exposure. Meeting the recommended LTPA level (7.5 to 15 MET-hours\/week) was associated with a 30 percent reduced all-cause mortality risk at PM2.5<\/sub>\u2009<25 \u03bcg\/m3<\/sup> but only 12 to 15 percent at >25\u2009\u03bcg\/m3<\/sup>. Pooled data from three cohorts (869,038 individuals; 45,080 deaths) confirmed this pattern. Among individuals meeting the recommended LTPA level, there was a lower risk for all-cause mortality versus those in the highest-risk group (reference,\u2009<\u20091 MET-hour\/week; PM2.5,<\/sub> 35\u201350 \u03bcg\/m3<\/sup>). Risk reductions varied by PM2.5 <\/sub>exposure (hazard ratios,\u20090.75, 0.67, 0.34, 0.34, and 0.30 for 35 to 50, 25 to 35, 15 to 25, 10 to 15, and <10 \u03bcg\/m3<\/sup>, respectively). Across most PM2.5<\/sub> exposure categories, higher levels of LTPA were generally associated with lower all-cause and cause-specific mortality, but the protective effects were attenuated at PM2.5<\/sub> levels >25\u2009\u03bcg\/m3<\/sup> for all outcomes and became nonsignificant for cancer mortality at 35 to 50 \u03bcg\/m3<\/sup>.<\/p>\n “Our findings emphasize that exercise remains beneficial even in polluted environments,” Ku said in a statement. “However, improving air quality can greatly enhance these health gains.”<\/p>\n