A recent meta-analysis showed that short-term (within five days) exposure to air pollution increases the risk of stroke. The study reviewed 110 studies involving more than 18 million stroke cases and found significant correlations between increased concentrations of pollutants such as nitrogen dioxide, ozone, carbon monoxide, sulfur dioxide and various particulate matter, and stroke incidence and related deaths.
A meta-analysis published online in Neurology, the medical journal of the American Academy of Neurology, on September 27, 2023, showed that short-term exposure to air pollution may be associated with an increased risk of stroke. Short-term exposure was defined as occurring within five days of stroke.
"Previous studies have established a link between long-term exposure to air pollution and an increased risk of stroke," said study author Ahmad Toubasi, MD, PhD, of the University of Jordan in Amman. "However, the association between short-term exposure to air pollution and stroke is less clear. In our study, instead of looking at exposure over weeks or months, we looked at just five days and found a link between short-term exposure to air pollution and an increased risk of stroke."
This comprehensive meta-analysis reviewed 110 studies, including more than 18 million stroke cases. Researchers studied pollutants such as nitrogen dioxide, ozone, carbon monoxide and sulfur dioxide. They also looked at particles of different sizes, including PM1 (air pollution less than 1 micron in diameter), PM2.5 and PM10. PM2.5 or smaller particles include inhalable particulate matter from motor vehicle exhaust, the burning of power plants and other industrial fuels, and forest and grassland fires. PM10 includes dust from roads and construction sites.
Research findings and implications
People exposed to higher concentrations of various types of air pollution are at increased risk of stroke. Higher concentrations of nitrogen dioxide increase the risk of stroke by 28%; higher concentrations of ozone, increase the risk of stroke by 5%; carbon monoxide increases by 26%; and sulfur dioxide increases by 15%. Higher concentrations of PM1 increase the risk of stroke by 9%, PM2.5 by 15%, and PM10 by 14%.
Higher levels of air pollution are associated with a higher risk of death from stroke. Higher concentrations of nitrogen dioxide increased the risk of stroke death by 33%, sulfur dioxide by 60%, PM2.5 by 9%, and PM10 by 2%.
"There is a strong and significant link between air pollution and the occurrence of stroke and death from stroke within five days of exposure. This highlights the importance of global efforts to develop policies to reduce air pollution. Doing so can reduce the number of strokes and their consequences," Tubas said.
A significant limitation of this meta-analysis is that it relies primarily on studies from rich countries, with very little data from low- and middle-income countries.