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A nationwide study in France found an association between extreme temperatures and worsening heart disease. Kenzo Tribouillard/Getty Images
  • Heatwaves that affect human health may occur more frequently due to climate change.
  • A nationwide study of 1,420 people with chronic heart failure in France reports that increased temperatures during a 2019 heatwave were closely linked to weight loss.
  • Weight monitoring for this condition is important because weight changes may result in lung congestion, the main cause of hospitalization.

In chronic heart failure, the heart is unable to pump blood around the body as efficiently as it should.

This allows waste products to accumulate, resulting in symptoms such as lung congestion, fluid buildup, edema, fluid retention, fatigue, dizziness, and irregular or rapid heartbeats.

Medicines such as diuretics, also known as water pills, are prescribed to people with heart failure to increase their urine output to help reduce any breathlessness and swelling. These medications increase the amount of water and salt that is expelled from the body in urine.

During the summer of 2019, Europe experienced an extreme heatwave, particularly in France.

Researchers at the University of Montpellier hypothesized there would be changes in weight among individuals with heart conditions during a heatwave and that these changes could be assessed using telemonitoring.

The findings, recently published in ESC Heart Failure, a journal of the European Society of Cardiology (ESC), examines the relationship between body weight and air temperature among people with heart disease.

Current ECS guidelines recommend that people with heart conditions should increase their diuretic dose or contact their doctor if they experience a change in symptoms or a sudden unexpected weight gain, as this can indicate a worsening of their condition.

Telemonitoring is an effective way of monitoring patients with heart failure, which uses technology to track a person’s weight in real time.

The telemonitoring protocol requires individuals to weigh themselves and input data into an electronic system, often using a smartphone. However, this method could impact both compliance and data collection if people are not instructed on how to input data correctly or if they simply forget to do so.

A benefit of telemonitoring is that it quickly transfers data to the clinic, where doctors and healthcare professionals can be alerted to take relevant action if necessary.

For the present study, researchers collected and analyzed data from people with heart disease using a system managed by CDM e-Health, an electronic chronic disease management system.

They looked at data from June 2019 to September 2019 to assess the effects of two heatwaves that occurred during this period.

Researchers studied the association between people’s weight, the ambient temperature on the same day, and the temperature two days prior to the weight measurement. They found a strong association between temperature and weight, with weight dropping as the temperature rose.

The researchers noted that the strongest relationship was found with temperatures two days prior to the weight measurement.

Dr. François Roubille, Ph.D., president-elect of the Heart Failure group from the French Society of Cardiology (FSC) and lead author of the study, told Medical News Today that “extreme temperature could have an effect on patients, especially those with heart failure.”

When healthy people drink more fluids during hot weather, the body regulates their urine output. This does not work in the same way for people with heart failure because they take diuretics.

Dr. Roubille explained that people with heart failure might find it difficult to adapt to heatwaves.

“Above all, they receive drugs that could lead to side effects under extreme temperature, for instance, diuretics,” he said.

The researchers noted that weight change in people with heart failure happens due to the pressure associated with a heatwave. The change in weight could ultimately be an indicator of a worsening of their clinical condition.

Dr. Tharusha Gunawardena, a cardiologist at Ipswich Hospital in the U.K., not involved in the study, told MNT that “the study is asking an important question which I think is being considered more widely and so is nice to see some data. The impact of climate change is complex, but it is clear that the impacts are multifarious and important.”

“Temperature change has the potential to impact the complex physiological homeostasis of patients who are otherwise negotiating a careful balance with heart failure. In certain [individuals], their condition can be quite friable; it would seem reasonable to expect an important effect that temperature might play perhaps due to a combination of effects on blood vessel size, compliance, and electrolyte balances.”

– Dr. Tharusha Gunawardena, cardiologist

In clinical practice, physicians should continue to consider the impact of extreme heat on their patients while also considering how their treatments may be affected.

Monitoring systems may help in this endeavor, particularly among those with more severe cases of heart disease.

Dr. Roubille highlighted the importance of sharing better information about the impact of climate change on heart disease with the public. But it’s not just about sharing information; it’s important that individuals with heart disease also understand the information they’re given.

That’s why clear communication with their doctors is essential. Communicating the science effectively could help people with chronic heart failure become better equipped to adapt.

Dr. Roubille notes that additional parameters could also be integrated into telemonitoring systems to help people with heart disease recognize how to adapt their medications and habits in response to situations such as heatwaves.

“Telemonitoring is an elegant tool for closely monitoring weight in patients with heart failure.”

– Dr. François Roubille, lead author of the study

Dr. Gunawardena agreed. “The study highlights the empowering movement to monitor patients comprehensively in their home setting, which can give patients more freedom with the reassurance of clinical oversight and may reflect a future change in the treatment paradigm for other chronic conditions,” he said.

In their paper, Dr. Roubille and colleagues note the “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.”

“Our duty is to prepare,” the researchers concluded.