Results of a UK biobank study show high levels of air pollution were associated with an increased risk of transition from health to a first stroke and subsequent progression to cardiovascular (CV) events and death.
“These results indicate that understanding and reducing the effects of air pollutants on different transition stages in stroke will be beneficial in managing people’s health and preventing the occurrence and progression of stroke,” study investigator Hualiang Lin, PhD, of Sun Yat-sen University School of Public Health, Guangzhou, China, said in a news release.
The study was published online in the journal Neurology.
A way to stop stroke progression?
The researchers assessed air pollution exposure in 318,752 people (mean age, 56) from the UK biobank database. None had a history of stroke or heart disease at the start of the study. Annual concentrations of air pollution near where people lived were estimated through land-use regressions.
During an average follow-up of 12 years, 5,967 people had a stroke, 2,985 developed post-stroke CVD, and 1,020 died.
After adjusting for confounding factors, every 5 µg/m3 increase in exposure to fine particulate matter (PM2.5) was associated with a 24% increase in transition from healthy to first stroke (hazard ratio, 1.24; 95% confidence interval, 1.10-1.40) and a 30% increase in transition from being healthy to dying (HR, 1.30; 95% CI, 1.21-1.40).
PM2.5 is less than 2.5 microns in diameter and includes fly ash from coal combustion. The World Health Organization recommends that annual PM2.5 exposure should not exceed 5 µg/m3.
Those who had a stroke during the study had an average exposure of 10.03 µg/m3 of PM2.5, compared with 9.97 µg/m3 for those who did not have a stroke.
The air pollutants nitrogen oxide and nitrogen dioxide were also associated with an increased risk of stroke and death, but the associations were weaker.
“More research is needed, but it’s possible that decreasing exposure to heavy levels of air pollution could play a role in reducing the progression of stroke,” Dr. Lin said.
“People can reduce their exposure by staying indoors on heavy pollution days, reducing their outdoor exercise, wearing masks to filter out particulate matter, and using air purifiers,” Dr. Lin added.
Public policy implications
Reached for comment, Steffen E. Petersen, MD, MPH, professor of cardiovascular medicine, Barts Health NHS Trust, London, said the study “elegantly confirms the increased risk of stroke due to air pollution in the UK Biobank population study but interestingly suggests that the impact of air pollution may continue to adversely impact cardiovascular health even after the stroke occurred.”
“This is further evidence to inform policymakers to tackle air pollution and get levels below the recommended levels,” Dr. Petersen said.
“On a personal level, everyone, including stroke patients, may wish to consider personal measures to reduce exposure to air pollution, such as avoiding walking along polluted streets and rather take a less polluted route away from the main roads,” Dr. Petersen added.
The study had no targeted funding. Dr. Lin and Dr. Petersen report no relevant financial relationships.
A version of this article first appeared on Medscape.com.