Climate change and hyponatremia-related hospital admissions in people with focal epilepsy exposed to carbamazepine or its derivatives

Objective: To estimate the proportion of individuals with focal epilepsy treated with at least one among carbamazepine (CBZ), oxcarbazepine (OXC), or eslicarbazepine (ESL), who were hospitalized due to hyponatremia-related symptoms in 2024, and to test the hypothesis that there is an association with climatic variables. Methods: We undertook a prospective study in which people with focal epilepsy treated with at least one of the target drugs and at least one attendance in 2024 formed the study cohort. Individuals who were admitted or seen as outpatients for hyponatremia in 2024 were considered cases and the rest considered controls. Climate analysis was performed in Lamezia Terme, Calabria, Italy. Results: Seventeen of the entire cohort of 105 (16.2%) had hyponatremia-related hospitalizations. Older age (odds ratio [OR] = 1.07, 95% confidence interval [CI] = 1.03–1.12; p =.001) and exposure to OXC/ESL compared to CBZ (OR = 4.15, 95% CI = 1.20–14.32; p =.02) emerged as significant predictors of the events. Thirteen of the 17 cases (76.5%) currently reside on the Calabria coastline. Twelve of 17 events (70.6%) occurred between June and August. Among climatic variables, heatwaves (OR = 4.87, 95% CI = 1.75–13.50; p =.002) and tropical nights (night-temperature ≥20°C) (OR = 2.72, 95% CI = 1.02–7.27; p =.046) were the most significant predictors of the events. Forecasting models based on 10 consecutive days of recordings prior to the events revealed trends of rising temperatures preceding the events. Significance: We report a high rate of hyponatremia-related hospitalizations among people with epilepsy occurring predominantly during summer. Climate change–related events, such as heatwaves and tropical nights, may trigger hyponatremia symptoms. Climate–regional vulnerability should therefore also be considered when selecting antiseizure medications and when counseling patients. We encourage interdisciplinary collaboration between clinicians and climate scientists in this emerging critical area.