The current blistering heat wave that is crippling the country may be even more dangerous for people taking certain medications. A new study found that that among people who suffered non-fatal heart attacks associated with hot weather, a large portion were taking beta-blockers and aspirin.

“Patients taking these two medications have higher risk,” said Kai Chen, first author of the study and an assistant professor at the Yale School of Public Health. “During heat waves, they should really take precautions.” According to a news release by the Yale School of Public Health, those precautions include staying in an air-conditioned room or visiting a public cooling center.

The study, which appeared online in Nature Cardiovascular Research, followed 2,494 cases in Augsburg, Germany that involved non-fatal heart attacks during hot weather months from 2001 to 2014. Researchers had previously determined that exposure to heat or cold made heart attacks more likely, but in this study, they looked at the patients’ medications to determine possible causes.

It turned out that users of beta-blockers or antiplatelet medications, such as aspirin, were likely to have their heart attacks during the hottest days compared to control days. Antiplatelet medication use was associated with a 63% increase in risk and beta-blockers with a 65% increase. People taking both drugs had a 75% increased risk, said the Yale press release.

While the study didn’t prove that the medications themselves raised the likelihood of heart attacks, a couple of factors did point out that the meds were the culprit. For one, younger people ages 25 to 59 who were presumed to be healthier than the older men and women, were more susceptible to having a heart attack when taking the drugs than older patients, ages 60 to 74.

Another clue was, for the most part, people taking other heart medications didn’t show a connection to heat-related heart attacks. An exception was cholesterol-lowering statins, which did increase the risk for heart attack on hot days threefold, says Yale.

“We hypothesize that some of the medications may make it hard to regulate body temperature,” said Chen, adding that he plans to delve further into the topic in future studies. The study also suggests that as climate change progresses, heart attacks might become a greater hazard to some people with cardiovascular disease.

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