Rising Global Temperatures May Worsen Heart Failure, Study Says

Extreme heat waves, which are becoming more frequent and longer lasting amid climate change, have a variety of serious ramifications, not the least of which is the impact on human health and wellness. Adding to the growing body of knowledge surrounding the impacts of climate change, a new study suggests that extreme heat could be particularly dangerous for those with heart failure.

Published in ESC Heart Failure, which is a journal of the European Society of Cardiology, the new study says that the increasingly common heat waves brought about by global warming could lead to a higher rate of “mortality in the general population, especially regarding cardiovascular mortality.”

Specifically, the observational study identified a relationship between the warmer temperatures brought about by heat waves and body weight change, which can be particularly dangerous for people with heart failure and worsen their condition.

"This suggests a direct impact of global warming on human health, with acute episodes that are expected to occur more often threatening patients with chronic diseases, especially the more fragile populations," the researchers wrote.

Here's a closer look at the study and the ramifications of its findings as climate change becomes more serious around the world.

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The Connection Between Heat Waves and Weight Loss

The study took place in France in 2019, a year that was marked by extreme heat waves across Europe. Between June and September of that year—a timeframe that included two extreme heat events—researchers used a telemonitoring system to track how heat impacted the weight of people who had a history of heart failure.

In patients with heart failure, the study explained, weight is the cornerstone of monitoring health because weight gain is related to congestion, the main reason for hospital admission. The authors of the study hypothesized that the body weight of patients with heart failure could change during a heatwave.

The study included 1420 individuals with a history of heart failure — 70% of whom were male. The average age of participants was 73 years old. In addition to tracking weight using telemonitoring, study participants were asked to report other symptoms they experienced such as fatigue, swelling, or breathlessness.

In the end, the data collection showed that as outdoor temperatures in France increased, patients' weights significantly decreased and their conditions worsened. Some patients weighing 78 kilograms lost 1.5 kilograms in a short period of time, the study said.

“The weight loss we observed during the heatwave was clinically relevant,” study author François Roubille, a professor with Montpellier University Hospital, France, said in a press release.

"This study is the first to show a strict relationship between ambient temperature and body weight in heart failure patients," Roubille added. "The finding is timely given the heatwaves again this year."

The Ramifications of Hotter Conditions

Monitoring weight was a crucial element of the study because any sudden changes in weight can be concerning among people with heart failure. As Roubille explained in the press release, the weight loss observed among study participants with heart failure had the potential to trigger other serious health ramifications including “low blood pressure, especially when standing up, and renal failure, and is potentially life-threatening.”

While extreme heat conditions cause everyone to lose more water than usual—mainly by increased sweating—among people with heart failure, this can be especially problematic. This is because heart failure patients typically take diuretics, which helps them rid their body of excess fluid by urinating more on a normal, day-to-day basis. If these patients’ bodies are losing more water than normal during a heatwave, however, the diuretics could leave them overly dehydrated.

Roubille explained that when healthy people drink more fluids during hot weather, the body can automatically regulate urine output. The same is not the case however for patients with heart failure because they take diuretics, Roubille said.

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Tips That Can Help Heart Failure Patients During Heatwaves

With rising temperatures on the horizon for the foreseeable future, clinicians and patients should be ready to reduce the dose of diuretics among heart failure patients when weight loss occurs, Roubille suggests in the study.

Many cardiologists already adjust patients’ diuretic doses in response to changes in weight, Kevin O’Brien,MD, a heart failure specialist and professor of medicine at the University of Washington School of Medicine who was not involved in the study, told Health. The study may suggest however, that this would be a particularly beneficial strategy during heat waves.

In addition, telemonitoring systems might also be useful moving forward in monitoring patients and indicating when a change in a person's dose of diuretics is needed based on routine weight monitoring, the authors write.

"These results suggest a new way to implement weight telemonitoring in [heart failure], such as paving the way for semiautomatic adaptations of the doses of diuretics," the authors write.

People with heart failure can also likely benefit from the same strategies that can keep anyone healthy during a heat wave, such as staying in a cool, indoor place.

In places where people do not have air conditioning in their homes, options might include going to air-conditioned public buildings or museums, visiting pools, or parks where it may be cooler than inside. Dr. O'Brien cautioned however, that these strategies may not work equally well for everyone.

These things won't "necessarily help the people that seem to be at most risk in this study, which were older patients," he said. These patients might be in worse health and less able to access places like pools and museums.

If you have a condition like diabetes, obesity, or high blood pressure that put you at risk for heart failure, lifestyle choices like eating healthy, exercising, and maintaining a healthy weight can keep you from developing heart failure, added Dr. O'Brien.

Ultimately, Dr. O'Brien said the study authors have identified an important challenge of treating heart failure during heat waves and proposed an innovative way to address it.

"This is a really important challenge to identify," said Dr. O'Brien. And with the increasing frequency and severity of heat waves, he added, "it's only going to get worse."