Air Pollution Exposure May Lead to Increased Risk of Stroke Within Five Days

A new meta-analysis shows a strong correlation between gaseous and particulate air pollutants and the incidence of stroke, finding that short-term air pollutant exposure was linked to higher occurrence and mortality rates of stroke.

The analysis, published in Neurology, reviewed 110 studies that included over 18 million stroke cases, looking at the effects of short-term exposure to pollutants such as nitrogen dioxide, ozone, carbon monoxide, and sulfur dioxide.

"Previous research has established a connection between long-term exposure to air pollution and an increased risk of stroke," said study author Ahmad Toubasi, MD, of the University of Jordan in Amman. "However, the correlation between short-term exposure to air pollution and stroke had been less clear. For our study, instead of looking at weeks or months of exposure, we looked at just five days and found a link between short-term exposure to air pollution and an increased risk of stroke."

Researchers examined several different sizes of particulate matter, including PM1, air pollution that is less than one micron (µm) in diameter, PM2.5, and PM10. According to the study, PM2.5 and smaller includes inhalable particles from motor exhaust, powerplant fuels, and forest and grass fires. PM10 refers to particles like dust from roads and construction sites.

The study found that exposure to several different air pollutants was associated with a higher risk of stroke. Higher concentrations of nitrogen dioxide were linked to a 28 percent increased risk of stroke; higher ozone levels were linked to a five percent increase; carbon monoxide exposure had a 26 percent increase; and sulfur dioxide had a 15 percent increase. 

When researchers broke down how different sizes of air pollution impacted the risk of stroke, they found that PM1 was linked to a nine percent increased risk, with PM2.5 at 15 percent and PM10 at 14 percent. Higher air pollution concentrations were also associated with an increased risk of death due to stroke. Higher nitrogen dioxide concentrations were linked to a 33 percent increased risk of death by stroke, while sulfur dioxide was linked to an increased risk of 60 percent.

"There is a strong and significant association between air pollution and the occurrence of stroke as well as death from stroke within five days of exposure," Toubasi said. "This highlights the importance of global efforts to create policies that reduce air pollution. Doing so may reduce the number of strokes and their consequences."

According to the study’s authors, most of the investigations included in the analysis were conducted in high-income countries, and more research is needed to understand the effects of air pollution on the health of people from lower-income countries.