The daily stress of a fast-paced life can increase anxiety and even the chances of a stroke, but now studies show that air pollution on its own may cause this too.

According to two studies published in The BMJ, air pollution has been linked to a greater risk of stroke and anxiety - especially in developing countries.

A team of researchers from Edinburgh University examined the association between short term air pollution exposure and stroke-related hospital admissions and deaths. In total, they reviewed the results of 103 observational studies that covered 28 countries across the globe.

They analyzed the effects of carbon monoxide, Sulphur dioxide, nitrogen dioxide and ozone by measuring the size of fine particles.

Results indicated that when people were exposed to carbon monoxide, there was a 1.5 percent increased risk of stroke per 1 ppm, a 1.9 percent of increased risk per 10 ppb of Sulphur dioxide, and a 1.4 percent increase per 10 ppb in the case of nitrogen dioxide. All of these pollutants were linked to stroke-related hospital admissions or death, especially in low- to middle-income countries. In higher income countries, the association was not as strong. The weakest association was found for ozone.

A second study from researchers at Johns Hopkins and Harvard Universities looked at the correlation between particulate air pollution and anxiety. The results showed that nearly 15% of women experienced high anxiety symptoms, which was linked to exposure to particulate matter. Additionally, women living 50 to 200 meters away from a major road were more likely to have a greater degree of anxiety than women living more than 200 meters away.

"[These studies] confirm the urgent need to manage air pollution globally as a cause of ill health... Air pollution could be a cost effective way to reduce the large burden of disease from both stroke and poor mental health," said Michael Brauer of the University of Columbia in an accompanying editorial.