A recent study indicated that exceeding the air pollution exposure limits recommended by the World Health Organization can increase the risk of first-time stroke. Hoaliang Lin from Sun Yat-sen University in China and his colleagues aimed to understand the risk of air pollution among individuals without a history of stroke. The study, published in the journal Neurology, stated: "We found that high levels of air pollution are associated with increased risks of transitioning from health to first stroke, cardiovascular events after stroke, and mortality, but with a stronger impact on transitioning from being healthy to having a stroke." Lin added, "These findings suggest that understanding and reducing the impact of air pollutants on different transitional stages of stroke will be beneficial for managing people's health and preventing stroke occurrence and development."
The study included 318,752 individuals in the UK Biobank database with an average age of 56. Participants had no prior history of stroke or heart disease at the study's start. Researchers examined individuals' exposure to air pollution based on where they lived at the beginning of the study and followed participants for an average of 12 years. During that time, 5,967 individuals experienced a stroke. Among them, 2,985 developed cardiovascular diseases, and 1,020 subsequently died.
Those exposed to high levels of air pollution were more likely to suffer a first stroke or experience cardiovascular diseases after stroke, or to die compared to those who were not exposed to high pollution levels. After adjusting for other factors that may play a role, such as smoking and physical activity levels, researchers found that for every 5 micrograms per cubic meter (µg/m³) increase in fine particulate matter, for example, the risk of transitioning from health to first stroke increased by 24%, and the risk of transitioning from health to death increased by 30%.
Particulates are composed of liquid or solid materials suspended in air. Fine particulate matter (PM2.5), which has a diameter of less than 2.5 micrometers, includes ash from coal combustion. Those who suffered 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 pollutants such as nitrogen oxide and nitrogen dioxide were linked to an increased risk of stroke and mortality. Lin revealed: "Further research is needed, but reducing exposure to high levels of air pollution may play a role in limiting the development of stroke. People can reduce their exposure by staying indoors on heavily polluted days, limiting outdoor exercise, wearing masks to filter particles, and using air purifiers." Lin emphasized that the results do not prove that air pollution causes stroke, cardiovascular diseases, or death, but only show an association.
