Impact of global warming on weight in patients with heart failure during the 2019 heatwave in France

Introduction Heatwaves affect human health and should be more and more frequent because of global warming and could lead to increase mortality in general population, especially regarding cardiovascular mortality. During the summer 2019, Europe experienced a strong episode of heatwave.Telemonitoring of patients with HF provide an elegant tool to monitor closely the weights and we assumed to be able to assess our hypothesis through a nation-wide telemonitoring system. Objective Here, we hypothesize that 1/there will be a change in patients’ weight during the heat wave and 2/that the telemonitoring would enable us to follow these changes. The change in weight would be a surrogate for clinical worsening (with or without decompensated HF). Method We collected and analysed the data from patients followed in the telemonitoring system managed by CDM e-Health, an Air Liquide Healthcare affiliate, between 1 June 2019 and 30 September 2019 to accurately catch the two heatwaves at the end of June and end of July. Results A total of 1420 patients (28% female) from 68 counties (representing more than 71% of the French territory), with a median age of 73.0 years and mean weight of 78.1kg, were included in this analysis. Pairs of data were included in the analysis when both their weight and the temperature where the patient lives were available (n=770). Thus, a total of 55,952 data points were included.Temperatures during the duration of the study are presented in Fig. 1A and weights in Fig. 1B. The relationship between temperature and weight was very strong (P<10-7, Fig. 1). As expected, there was a strong relationship between patient weight and the probability of an alert (from clinical evaluation, P<10-16).Daily temperature −2 days was significantly related to alerts (P=0.002). Conclusion We reported a strict relationship between temperature and body weight in patients with HF for the first-time in a nation-wide observational study. The magnitude of the effect seems to be clinically relevant, with a variation of 1.5kg over a short period.This could expose patients to increased symptoms, HF decompensation, and poor outcomes. These results suggest a new way to implement weight telemonitoring in HF, such as paving the way for semiautomatic adaptations of the doses of diuretics.