A nationwide study in France reported that heat waves from global warming could have a detrimental effect on heart disease patients. According to the report, heart patients lost 1.5 kg weight during the heat waves between 1 June and 20 September 2019, indicating a worsening condition. The study is published today in ESC Heart Failure, a journal of the European Society of Cardiology (ESC)
Heart failure is a chronic, progressive condition in which the heart muscle cannot pump enough blood to meet the body's needs for blood and oxygen. Blood often backs up and causes fluid to build up in the lungs and the legs, causing shortness of breath and swelling in the lungs, legs, and abdomen. Heart patients are often prescribed diuretics, also known as "water pills," to help the kidneys eliminate unneeded water and salt. This makes it easier for your heart to pump and reduces breathlessness and swelling.
It is also essential to monitor the weight of heart patients because studies show that weight gain is related to congestion, the main reason for hospital admission. However, weight loss due to higher temperature hasn't been investigated.
In the current study, researchers hypothesized that in heart failure patients' their body weight could change during a heatwave.
When healthy people drink more fluids during hot weather, the body automatically regulates urine output. This does not apply to patients with heart failure because they take diuretics," explained François Roubille, study author and professor at Montpellier University Hospital, France.
The report included 1,420 patients with chronic heart failure. The median age of the participants was 73 years, 28% were women, and the average weight was 78 kg. Researchers analyzed the relationship between body weight and air temperature between 1 June and 20 September 2019, which covered the two heatwaves at the end of June and the end of July.
A national telemonitoring system was used to obtain information on weight and symptoms remotely. Patients weighed themselves daily using a connected weighing scale that automatically sent measurements to the clinic.
Patients reported daily symptoms such as edema, fatigue, breathlessness, and cough by answering questions on a personal device (e.g., smartphone, tablet), with answers sent automatically to the clinic. Daily temperatures (at noon) were obtained using data from the closest weather station to each patient's home.
The results showed that the participant's weight dropped as the temperature increased. The most vital relationship was found with temperatures two days before the weight measurement.
"The weight loss we observed during the heatwave was clinically relevant. Patients weighing 78 kg lost 1.5 kg in a short period. We were surprised to see that weight dropped with hot temperatures, as we had expected the opposite. For this reason, the telemonitoring system was programmed to alert clinicians when patients gained weight."
It's not clear precisely why temperature shifts are correlated with weight loss. But this could be due to diuretics, which lead to excessive water loss from the body. Experts believe that extreme temperature shifts affect the body's ability to regulate normal temperatures. This puts extra strain on the heart and body to keep its core temperature to normal levels.