It may seem like an obvious link; inhaling polluted air simply cannot be good for the cardiovascular system. But science demands measurable outcomes to make a conclusion, and rightly so. New research shows that climate change and overall air quality – including higher pollution levels – are linked to a higher number of strokes.

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The researchers used data from China and the US – “the world’s two largest emitters of greenhouse gases,” according to Dr. Longjian Liu.

The latest results were presented at the American Stroke Association’s International Stroke Conference 2016, which takes place February 17th-19th, in Los Angeles, CA.

Each year in the US, stroke kills nearly 130,000 people, which is 1 out of every 20 deaths. And worldwide, stroke is the second leading cause of global death, trailing heart disease.

To conduct their study, researchers used data from “the world’s two largest emitters of greenhouse gases,” which are responsible “for about one third of global warming to date,” says lead study author Dr. Longjian Liu, from Drexel University in Philadelphia, PA.

The two countries are the US and China.

Dr. Liu and his colleagues explain that their study is one of the first to look into the interaction between air quality and stroke prevalence alongside temperature.

To carry out their research, the team looked at air quality data collected in 2010-2013, from 1,118 counties in 49 states in the US – and from 120 cities in 32 Chinese provinces.

Fast facts about stroke
  • In the US, stroke kills almost 130,000 people each year
  • On average, every 4 minutes, one American dies from stroke
  • Each year, stroke costs the US $34 billion.

Learn more about stroke

They explain that particulate matter (PM) is air particles including dust, dirt, smoke and water droplets. The greatest health risks arise from particles that are less than 2.5 μm in diameter (PM2.5).

Such particles are 1/30th the diameter of a human hair, are not visible to the human eye and are created from car, power plant and forest fire combustion.

After studying the data, the researchers observed that the total number of strokes increased by 1.19% for each 10 μg/m3 increase of PM2.5. Furthermore, they found significant regional differences in PM2.5 levels linked to stroke prevalence.

In detail, southern America had the highest average annual PM2.5. Interestingly, the South has the highest prevalence of stroke, at 4.2%.

Conversely, the West had the lowest average annual PM2.5, and this region of the US has the lowest stroke prevalence, at 3%.

An additional finding from their study revealed that temperature impacts air quality and stroke risk. Dr. Liu says climate changes can be partially accountable for seasonal air quality variations:

In the summer, there are lots of rainy and windy days, which can help disperse air pollution. High temperatures create a critical thermal stress that may lead to an increased risk for stroke and other heat- and air quality-related illnesses and deaths.”

He also notes that “patients with stroke are in danger of dehydration due to high temperatures in the summer, and are in danger of suffering from pneumonia, influenza and other respiratory diseases in winter.”

Of course, we are not able to control air quality, but Dr. Liu says their findings provide proof to policy makers and leaders of public health. From this research, he hopes they will be able to develop better models for monitoring and predicting climate change so patients can be prepared.

Another group that is particularly vulnerable to stroke risk as a result of air quality is women and the elderly.

Medical News Today recently reported on a study that suggested air pollution is linked to premature birth.