Air Pollution Linked to Increased Risk of Stroke, Anxiety

Air pollution has reportedly been linked to irregular heart beat and blood clots, and now new research suggests that it may lead to an increased risk of stroke and anxiety as well, especially in developing countries.

Usually factors like obesity, smoking and high blood pressure put people at a great risk of stroke, which kills around five million individuals each year worldwide. However the effect of the environment, including air pollution, remains to be seen due to a lack of evidence.

So a team from Edinburgh University decided to delve further into the association between short term air pollution exposure and stroke related hospital admissions and deaths. Their findings were published in the journal The BMJ.

They looked at gaseous pollutants including carbon monoxide, sulfur dioxide, nitrogen dioxide and ozone. In addition, particulate matter was included: PM 2.5 (fine particles less than 2.5 µm in size) and PM 10 (coarse particles less than 10 µm in size). In total, they analyzed 103 observational studies that covered 28 countries across the world.

They found a link between carbon monoxide (1.5% increased risk per 1 ppm), sulfur dioxide (1.9% per 10 ppb) and nitrogen dioxide (1.4% per 10 ppb) and stroke related hospital admissions or death. Meanwhile ozone exhibited the weakest association.

Both PM 2.5 and PM 10 also led to an increase in hospital admissions or deaths due to stroke, by 1.1 percent and 0.3 percent per 10 µg/m3 increment, respectively.

These findings "confirm the urgent need to manage air pollution globally as a cause of ill health" and that reducing "air pollution could be a cost effective way to reduce the large burden of disease from both stroke and poor mental health," Michael Brauer from the University of British Columbia, who was not involved in the study, said in a statement.

This is especially true for low- to middle-income countries, which experienced the strongest associations between air pollution and stroke compared to high-income countries.

Previous research has shown that air pollution can affect the cells that line the circulatory system and increase activity of the sympathetic nervous system, which can lead to narrow blood vessels, an increase in blood pressure, the restriction blood supply to tissues and increase the risk of thrombosis (blood clot). (Scroll to read on...)

But air pollution isn't just associated with a higher risk of stroke, but with anxiety as well - the most common psychiatric disorder around the globe that affects around 16 percent of people at some point in their lives.

So in a second study, researchers at The Johns Hopkins and Harvard Universities examined the association between particulate air pollution and anxiety. After studying about 72,000 women, aged 57-85 years old, they realized that around 15 percent of women experienced high anxiety symptoms, mostly likely due to exposure to particulate matter. Though, while PM2.5 was found to have a significant association with anxiety, the same could not be said for PM 2.5-10.

And it turns out that the closer these participants lived to a major road (50 to 200 meters), the more they were at risk of developing anxiety.

Furthermore, when it pertains to both anxiety and stroke risk, the effects were strongest following the first month of exposure to the studied pollutants. Nevertheless, both studies, while they establish a link between the two factors, do not demonstrate a cause-and-effect relationship.

Man-made air pollution may date as far back as the 16^th century during the time of the Incas, but it has since escalated to a worldwide problem, now making us fear for our health.

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