Increased ambient temperature and hyponatraemia presentations: A ten-year retrospective study at an Australian hospital.

Abstract

To determine the relationship between ambient air temperature and the incidence of hyponatraemia in a heat-prone region. We conducted a retrospective study that correlated serum sodium concentrations documented at The Austin Hospital in Melbourne over ten years from January 2014 to December 2023, with publicly available temperature data from the Australian Bureau of Meteorology. Serum sodium concentrations and incidence of hyponatraemia admissions when correlated to temperature, and following heatwave events, defined as temperature above 30°C over five consecutive days. Over this period, 45718 low serum sodium results were identified from 26557 unique patients. Serum sodium concentrations in January (Australian Summer) were 0.55mmol/L lower (95% CI 0.36 to 0.77, p < 0.001) compared to September (Australian early Spring). Women had lower sodium concentrations compared to men (-0.21 mmol/L, 95% CI -0.29 to -0.12, p<0.001), as did patients older than 80 years when compared to those younger than 65 years (-0.39 mmol, 95% CI -0.50 to -0.29, p<0.001). Hospital admissions with hyponatraemia were more frequent during summer months. Profound hyponatraemia admissions (sodium ≤125 mmol/L) were more frequent following a heatwave, compared to without (7.6% vs 6.5%, p=0.04). Our study demonstrates that serum sodium concentrations are lower and profound hyponatraemia-related hospital admissions higher when ambient temperatures are warmer. This suggests that hyponatraemia is a climate associated health issue. Local public health advice for water consumption during heatwaves should consider this risk, and prompt action to limit climate change is required to mitigate this risk.