Air Pollution Correlates with Risk and Outcome of Stroke

Exposure to air pollution tends to inversely correlate with wealth and socioeconomic status, both of which clearly correlate with health in epidemiological studies. More careful studies of similar populations with differing exposure, and what is known of the biochemistry of tissue interaction with particulate matter, make it reasonable to think that the effects of particulate air pollution on chronic inflammation - and thus pace of development of atherosclerosis - play a role in the comparatively poor health of those people in regions of greater pollution. One of the outcomes of atherosclerosis is stroke, and as noted here, particulate air pollution correlates with greater risk of stroke and worse outcomes following stroke.

The study involved 318,752 people in the UK biobank database with an average age of 56. The participants did not have a history of stroke or cardiovascular disease at the start of the study. Researchers looked at people's exposure to air pollution based on where they lived at the start of the study. The participants were followed for an average of 12 years. During that time, 5,967 people had a stroke. Of those, 2,985 people developed cardiovascular diseases and 1,020 people later died. People exposed to high levels of air pollution were more likely to have a first stroke, post-stroke cardiovascular disease or death than people not exposed to high levels of pollution.

After adjusting for other factors that could play a role, such as smoking and physical activity level, researchers found that for each 5 micrograms per cubic meter (µg/m3) increase of fine particulate matter, for example, the risk of transitioning from being healthy to having a first stroke increased by 24% and from being healthy to dying the risk increased by 30%. Particulate matter consists of liquids or solids suspended in air. Fine particulate matter, PM2.5, is less than 2.5 microns in diameter and includes fly ash from coal combustion. Those who had a stroke during the study had an average exposure of 10.03 µg/m3 of PM2.5, compared to 9.97 µg/m3 for those who did not have a stroke. The researchers also found that the pollutants nitrogen oxide and nitrogen dioxide were associated with an increased risk of stroke and death.


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