Heat Waves Might Increase Heart Attack Risk for People on These Medications

Extreme heat can increase the risk of heart attacks, especially for people who are taking certain heart medications.

A new study found that people who took beta-blockers (which can lower stress on the heart) and antiplatelet drugs (which prevent blood clots) had a 75% higher risk of heat-related non-fatal heart attack than those who took neither medication.

The study, conducted by researchers from the Yale School of Public Health and several institutions in Germany, used a temperature of about 24 C (about 75 F) as a benchmark for high heat.

“These past few weeks, heat waves have been hitting everywhere in the world. As heat waves become more intense and more frequent, patients who are taking these two medications should take special care to stay cool,” lead study researcher Kai Chen, PhD, an assistant professor of epidemiology at the Yale Institute for Global Health, told Verywell.

Chen explained that the results do not suggest patients should discontinue using these two drugs, but rather they should take extra precautions during a heat wave.

Why Is Heat Harmful to the Heart?

Heat can cause physiological changes in the body, such as dilation of blood vessels, increased heart rates, or increased demand for the heart to pump harder, according to Jennifer Wong, MD, FACC, medical director of non-invasive cardiology for the MemorialCare Heart & Vascular Institute at Orange Coast Medical Center.

“These changes can be adapted to and may help healthy individuals bring down their internal body core temperatures,” Wong told Verywell. “But a person with heart disease may have less reserve to tolerate these hemodynamic changes, leading to cardiovascular complications like heart attacks.”

Similar to dehydration, enduring high heat may cause local and systemic inflammation in the body, Chen said. For some people, this could lead to complications like endothelial dysfunction, impaired circulation, and heart attacks.

In contrast, cold weather may also harm heart health. According to a 2018 study in Sweden, cold temperatures can slow blood flow to the heart and increase the risk of blood clots, which can also lead to heart attacks.

How Hot Is Too Hot?

According to Chen, high heat is relative to the average temperature of an environment. People in typically cooler regions, such as the northeastern United States, may have a higher heart attack risk at a lower temperature threshold than people who live in a naturally hotter climate.

“People tend to adapt to their local climate,” Chen said. Architectural designs like indoor air conditioning or cultural norms like afternoon naps are some ways that people have adapted to heat, he added.

The Yale study focused on 2,494 cases of non-fatal heart attacks in Augsburg, Germany, between May and September, from 2001 to 2014. These are considered Germany’s hot weather months and temperatures typically fall around 70 F.

Cool Off, Heart Medications Are Still Helpful

Despite the study results, people taking beta-blockers or antiplatelet medications should not be discouraged from starting or continuing either medication, Chen said. Rather, they should recognize their increased risk and take steps to keep themselves cool during a heat wave.

For one, the researchers did not prove that taking beta-blockers or antiplatelet medications caused the patients’ increased risk, but only found the associations, Chen explained. Aside from the medications, the participants had pre-existing conditions that may be responsible for their heart attack risk, he added.

Wong agreed that more research is needed to determine causation.

“Perhaps some physiologic changes are being blunted by the medications, but this may also be a matter of the population we’re looking at,” Wong said. “These are the folks who are vulnerable.”

However, the medications may not be harmless, either. The study found that, even when separating the patients by age, younger patients taking beta-blockers or antiplatelet medications were more susceptible to heat-related heart attacks than older patients who did not take the medications. The difference was even more pronounced for younger patients taking statins.

The researchers hypothesized that the medications may impair the body’s ability to regulate temperature.

“There’s a plausible reason that the medications may complicate the human body’s thermal regulation, but there’s potential for confounding indications,” Chen said. “One of the things we really try to want to convey is that this study does not suggest that these two drugs should not be taken.”