Heatwaves and arrhythmia among antidepressant and antipsychotic users, France, 2016-2024

Background Antipsychotics and antidepressants are widely prescribed and associated with adverse cardiovascular events, including arrhythmia. They impair thermoregulation, increasing vulnerability to extreme heat. This study assessed whether heatwaves increase the risk of arrhythmia-related hospitalization among antipsychotic and antidepressant users. Methods Hospitalizations for cardiac arrhythmia among adults using antipsychotics or antidepressants during summer period (2016-2024) were identified from the French National Health Data System and linked to daily meteorological data from Météo-France. Heatwaves were defined at the commune level as periods ≥3 consecutive days with mean daily temperature above the local 97.5th percentile, including ≥1 day above the local 99.5th percentile. A time-stratified case-crossover design with conditional logistic regression assessed short-term associations, examining heatwave exposure on the day of admission (lag 0) and during the three preceding days (lags 1–3). Results A total of 35633 arrhythmia-related hospitalizations were identified. Cases were mostly older adults (79.7 ± 11.9 years) and women (57.6%). Overall, 481 hospitalizations occurred during heatwaves. Globally, heatwave exposure was not associated with arrhythmia-related hospitalization (OR = 1.08, 95%CI 0.97–1.2). Among drug-induced arrythmia cases (ICD-10: I472, I4721, I498), any heatwave exposure within the 3 days preceding admission was associated with an increased risk of hospitalization (OR = 1.94, 95% CI 1.1–3.4). Particularly, the risk increases if exposed one day prior to admission (OR = 3, 95% CI 1.39–6.47) and two days prior to admission (OR = 3.21, 95% CI 1.55–6.66). Conclusions Patients under psychotropics may be vulnerable during heatwaves, which may increase hospitalization risk as observed in drug-induced arrhythmia. There is a need for more public health prevention strategies to reduce heat-related risk for this population during extreme heat. Key messages • Heatwaves may increase the risk of drug-induced arrhythmia hospitalization among antipsychotic and antidepressant users. • The findings support targeted prevention strategies for psychotropic drug users during periods of extreme heat.