One of the fears associated with global warming—in addition to melting glaciers and rising sea levels—is a change in the pattern of human disease due to hotter temperatures. For example, researchers linked higher temperatures related to climate change with an increased risk of stroke.
The study, presented at the American Stroke Association’s International Stroke Conference 2016, looks at data gathered in both the United States and China. The two countries “are the world’s two largest emitters of greenhouse gases and responsible for about one-third of global warming to date,” says Longjian Liu, MD, PhD, lead study author and an associate professor of Epidemiology and Biostatistics at Drexel University in Philadelphia.
The researchers looked at particles in the air (dust, dirt, smoke, and liquid droplets) that are smaller than 2.5 micrometers in diameter. These tiny particles are invisible to the naked eye, and their size makes them a health risk. Particles of this size result from combustion, such as that from forest fires, power plants, and vehicles.
In both the United States and China, researchers found that instances of stroke increased in relation to higher levels of particles. In the United States, the southern region of the country had the highest particle rates. People in the south also had the highest prevalence of stroke (4.2 percent) compared to other regions with lower air pollution rates.
Researchers determined that the weather could also affect the presence of these tiny particles in the air, and therefore, risk of stroke.
“Seasonal variations in air quality can be partly attributable to the climate changes,” Liu says. “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.”
Moreover, Liu added, “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. Women and the elderly also appear more vulnerable to stroke risk due to air quality and heat-related diseases.”
Stroke is the fifth leading cause of death in the United States, responsible for one in every 20 deaths, or a death every four minutes. The American Stroke Association reports that stroke is the leading cause of preventable disability in the U.S.
While Liu points out that patients themselves have little control over the quality of the air they ingest, he hopes the findings will encourage health leaders and lawmakers to work to monitor and predict climate change so patients have more protection.