Climate change may lead to a significant uptick in heart attacks, based on a University of Michigan study that found heart attacks often follow dramatic changes in outdoor temperature.
There’s a large body of evidence linking the temperature—mainly cold weather—to increased heart risks. However, this is the first study of its kind to explore the impact of sudden temperature changes on heart attack rates.
The new research will be presented this week at the American College of Cardiology’s 67th Annual Scientific Session—a meeting that brings together heart specialists from around the world to share the latest in treatment and prevention. The study included data from more than 30,000 patients treated for heart attack at 45 Michigan hospitals between 2010 and 2016.
After linking the data with weather records, researchers found that greater temperature fluctuation was associated with significantly higher rates of heart attack. Overall, heart attack risk increased by about 5% for every 9 degree fluctuation in temperature. Swings of more than 45 degrees were also associated with a greater increase in heart attack risk than smaller changes (18–45 degrees) in temperature.
Researchers note that this effect was even more pronounced on warmer days, meaning that fluctuations in temperature were more likely to trigger heart attacks in warmer weather.
In this study, daily temperature fluctuation was defined as the difference between the highest and lowest temperature recorded on the day of the heart attack.
The findings highlight the impact of our environment on heart health. "Generally, we think of heart attack risk factors as those that apply to individual patients and we have, consequently, identified lifestyle changes or medications to modify them," said senior author Hitinder Gurm, MD, professor of medicine and associate chief clinical officer at Michigan Medicine.
He encourages a similar approach when addressing environmental factors that impact cardiovascular risk.
"Temperature fluctuations are common and [often] predictable," says Gurm. "More research is needed to better understand the underlying mechanisms for how temperature fluctuations increase the risk of heart attacks, which would allow us to perhaps devise a successful prevention approach."
According to authors, research will become increasingly important as concerns around climate change grow.
"Global warming is expected to cause extreme weather events, which may, in turn, result in large day-to-day fluctuations in temperature," said Hedvig Andersson, MD, a cardiology researcher at the University of Michigan and the study’s lead author. "Our study suggests that such fluctuations in outdoor temperature could potentially lead to an increased number of heart attacks and affect global cardiac health in the future."