MI Often Follow Dramatic Changes in Outdoor Temperature

Findings suggest climate change may increase MI risk.

Hedvig Andersson, MD

Data presented at the 67th American College of Cardiology’s Annual Scientific Session demonstrated that drastic changes in temperature was associated with significantly more myocardial infarctions.

Then new findings suggest that climate change could lead to an increase in the occurrence of myocardial infarctions.

“Global warming is expected to cause extreme weather events, which may, in turn, result in large day-to-day fluctuations in temperature,” lead author, Hedvig Andersson, MD, cardiology researcher, University of Michigan, said in a statement.

Myocardial infarction can be triggered by environmental stress but there are few data on the impact of outdoor temperature on the risk of ST-elevation myocardial infarction (STEMI).

Evidence shows that outdoor temperature affects the rate of heart attacks, with cold weather bringing the highest risk. This new study is among the first to examine associations with sudden temperature changes.

The research is based on data from more than 30,000 patients treated at 45 Michigan hospitals between 2010—2016. All patients received percutaneous coronary intervention after being diagnosed with STEMI.

Researchers obtained a daily minimum, maximum and average temperatures on hospital zip code level. Absolute temperature changes was defined as the maximum difference in temperature on the day of STEMI presentation and the day before.

Overall, results showed that the risk of myocardial infarction increased by 5% for every 5-degreee jump in temperature differential — 9 degrees Fahrenheit.

Swings of more than 45 degrees Fahrenheit were associated with a greater increase in myocardial infarction compared to a smaller increase with temperature swings of 18—45 degrees Fahrenheit.

On days with a higher average temperature, the effect was more pronounced. At the other side of the spectrum, on a hot summer day, nearly twice as many myocardial infarctions were predicted on days with a temperature fluctuation of 63—72 degrees Fahrenheit than on days with no fluctuation.

In the analysis, researchers adjusted for precipitation totals, day of the week and seasonal trends in order to isolate the effects of daily temperature fluctuations from other potential environmental factors.

Sudden outdoor temperature changes, especially at higher baseline temperature, are associated with risk higher of STEMI. The anticipated increase in temperature fluctuation and rise in average daily temperatures associated with Global Warming may result in an increase in the incidence of STEMI.

Researchers emphasized that it is important to focus on modifiable cardiovascular disease risk factors, as the association does not necessarily prove that sudden temperature swings are the cause of the increase in heart attacks.

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