Climate Change May Increase Heart Attack Risk

A new study suggests that large day-to-day swings in temperature are associated with significantly more myocardial infarctions (MIs).

Researchers at the University of Michigan (U-M; Ann Arbor, USA) reviewed data from over 30,000 patients treated at 45 Michigan hospitals between 2010 and 2016. All patients had received percutaneous coronary intervention (PCI) after being diagnosed with ST-elevated MI. The researchers calculated the daily temperature fluctuation--defined as the difference between the highest and lowest temperature--preceding each MI, based on weather records for the hospital's ZIP code. The researchers also adjusted for precipitation totals, day of the week, and seasonal trends to isolate the effects of daily temperature fluctuations from other potential environmental factors.

Overall, the results showed the risk of MI increased by about 5% for every five-degree (Celsius) jump in temperature differential. Swings higher than 25 degrees were associated with a greater increase in heart attack rates, compared to a smaller increase with temperature swings of 10-25 degrees. The effect was more pronounced on days with a higher average temperature. On a hot summer day, nearly twice as many heart attacks occurred as on days with a temperature fluctuation of 35-40 degrees than on days with no fluctuation. The study was presented at the American College of Cardiology (ACC) 67th annual scientific session, held during March 2018 in Orlando (FL, USA).

“Global warming is expected to cause extreme weather events, which may, in turn, result in large day-to-day fluctuations in temperature,” said lead author Hedvig Andersson, MD, a cardiology researcher at U-M. “While the body has effective systems for responding to changes in temperature, it might be that more rapid and extreme fluctuations create more stress on those systems, which could contribute to health problems.”

“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 Professor Hitinder Gurm, MD, of U-M. “Temperature fluctuations are common and [often] predictable. 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.”

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