French study shows hot temperatures cause heart failure to worsen

A nationwide study in France is the first to show that as temperatures continue to climb, they are causing patients with heart failure conditions to deteriorate.  

Scientists have discovered that during the 2019 heatwave, high temperatures were linked with weight loss in people who suffer with heart failure, worsening their condition.   

Professor Francois Roubille of Montpellier University Hospital has said the study is the first to show ‘a strict relationship between ambient temperature and body weight’ in heart failure patients.   

He said: ‘The finding is timely given the heatwaves again this year. The weight loss we observed in people with heart failure may lead to low blood pressure, especially when standing up, renal failure and is potentially life threatening.’   

The study examined the relationship between body weight and air temperature between June 1 and September 20 2019, which covered the two heat waves experienced in June and July.  

Scientists observed 1,420 patients with chronic heart failure – 28% were women and the medium age was 73. The average weight of the patients was also 78kg.   

A national telemonitoring system was used to gain information on patients’ weight and any symptoms they developed. They reported experiencing fatigue, oedema, breathlessness and a cough.   

The people involved in the study weighed themselves everyday using a connected scale that automatically sent their measurements to the clinic and daily temperatures at 12pm were obtained using data from the closest weather station to each patient’s home.  

Researchers analysed the association between patient weight and temperature on the same day and temperature two days prior to the weight measurement.   

They found that the relationship between temperature and body weight was very strong, with weight dropping as the temperature rose.   

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

Weight loss in people who suffer with a heart condition has received little attention compared to those who gain weight.   

Professor Roubille said: ‘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.’  

When studying the effects of the 2019 heatwave, Professor Roubille noted heart failure patients who weighed 78kg lost 1.5kg in a short period of time.   

‘We were surprised to see that weight had dropped with hot temperatures, as we had expected the opposite,’ Professor Roubille said, ‘Given the expectation of more heatwaves, telemonitoring systems need to alert clinicians of weight loss in heart failure patients.’ 

The study has been published in the European Society of Cardiology (ESC) journal. 

Photo by Ali Hajiluyi