Could climate change be affecting STEMI rates?

By Liz Meszaros, MDLinx
Published March 13, 2018

Key Takeaways

An increased risk of ST-elevation myocardial infarction (STEMI) is associated with sudden changes in outdoor temperatures, especially when the baseline temperature is higher, according to results presented at the American College of Cardiology’s 67th Annual Scientific Session held March 10-12, 2018.

These results may have a great impact in the future because of anticipated increases in average daily temperatures associated with climate change, or global warming, which portends an increase in the incidence of STEMI.

“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, cardiology researcher, University of Michigan, Ann Arbor, MI. “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.”

Dr. Andersson and colleagues identified all STEMI patients treated with percutaneous coronary intervention (PCI) in Michigan from 2010 to 2016. Using hospital zip codes, they collected information on daily minimum, maximum, and average temperatures. They defined absolute temperature change (ΔT) as the maximum difference in temperature on the day of STEMI presentation and the day before.

Researchers then used hierarchical generalized linear mixed effects regression modeling with Poisson likelihood and a zip code random intercept to assess any association between ΔT and STEMI events.

In all, they identified 30,404 patients with STEMI who presented to 45 hospitals. The mean number of patients presenting per day ranged from 0 to 1 (95% CI: 0-2) between hospitals. The mean ΔT was 13° C (IQR: 10°-16° C).

A larger ΔT was associated with an increased risk of STEMI (RR: 1.02; 95% CI: 1.00-1.03; P=0.011 for every 5° C change). Swings of 10° to 25° C caused smaller increases. These effects were greater on warmer days.

Many previous studies have documented the effects of cold weather on the incidence of MI, but this study was one of the first focused on sudden changes in temperature.

Why this association occurs, Dr. Andersson remarked, is not known.

“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,” she said.

“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. Population-level risk factors need a similar approach,” said senior author Hitinder Gurm, MD, professor of medicine and associate chief clinical officer, Michigan Medicine. “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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