Air pollution, even at low levels, linked to higher ischemic stroke risk in some groups
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Key takeaways:
- Ischemic stroke incidence was higher among women younger than 65 years exposed to air pollution.
- Smoking and drinking alcohol may further increase negative effects of air pollution.
Exposure to air pollution was linked to higher ischemic stroke incidence among women younger than 65 years and residents of areas with high alcohol and tobacco consumption, researchers reported in European Journal of Preventive Cardiology.
This association occurred even at low levels of air pollution exposure, results showed.
“The long-term impact of air pollution on CVDs has been well established in the scientific literature; however, short-term effects have not yet been well studied, especially in relation to Polish smog and ischemic stroke incidence in the region of Eastern Europe,” Michał Święczkowski, MD, of the department of invasive cardiology at the Medical University of Biaystok in Poland, and colleagues wrote. “Understanding these dependencies is exceptionally important for health care planning and resource allocations.”
To analyze the association between short-term exposure to air pollution and ischemic stroke incidence, wiczkowski and colleagues conducted a retrospective, population-based cohort study of 8 million participants from an EP-PARTICLES cohort from 2011 to 2020 in eastern Poland.
The primary outcome of the study was incidence of ischemic stroke — based on data on emergency hospitalizations from Poland’s National Health Fund — and its association with short-term exposure to air pollutants, including fine particulate matter (PM2.5), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), benzo(alpha)pyrene (BaP) and carbon monoxide (CO), using data based on the municipality level.
wiczkowski and colleagues analyzed the association using quasi-Poisson models that included temperature, relative humidity, atmospheric pressure, day of the week, bank holidays, influenza seasons, SARS-CoV-2 pandemic and seasonal trends as covariates.
During the study period, the researchers recorded 146,262 cases of ischemic stroke (median age, 76 years; 51.8% women), with an in-hospital mortality rate of 14.92%.
The researchers found a correlation between exposure to air pollutants and increased risk for ischemic stroke onset on the day of exposure, including a 2.4% increased risk due to PM2.5 exposure (RR = 1.02; 95% CI, 1.02-1.03), a 1% increased risk due to NO2 exposure (RR = 1.01; 95% CI, 1-1.02), a 0.8% increased risk due to BaP exposure (RR = 1.01; 95% CI, 1-1.02) and a 0.6% increased risk due to SO2 exposure (RR = 1.01; 95% CI, 1-1.01).
They also observed more pronounced effects of exposure to PM2.5, NO2 and BaP among individuals younger than 65 years and women (P for interaction < .001).
Exposure to PM2.5 (P for interaction < .001) and SO2 (P for interaction = .025) was strongly associated with ischemic stroke incidence in residents of regions with high tobacco consumption, according to the researchers.
Similarly, exposure to PM2.5 (P for interaction < .001), NO2 (P for interaction = .007) and SO2 (P for interaction < .007) was strongly associated with ischemic stroke incidence in residents of regions with high alcohol consumption.
The researchers also evaluated exposure-response curves and noted that the slopes were nonlinear and steeper at lower concentrations (PM2.5 < 20 µg/m3; NO2 < 10 µg/m3; BaP < 1 µg/m3; SO2 < 2 µg/m3).
“Such exposure-response relationship curves in environmental studies are pivotal for assessing the benefits of air pollution concentration-reducing policies, suggesting that there is no ‘safe’ level of air pollution,” the researchers wrote.
The researchers acknowledged several study limitations, including their utilization of residential ZIP codes to connect individual exposure and ischemic stroke incidence, “which may result in potential misclassifications due to outdated codes and people’s mobility, even though we used the [Global Environmental Multiscale – Air Quality] model to minimize such risk,” they wrote.
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