Short-term association between outdoor temperature and the hydration-marker copeptin: a pooled analysis in five cohorts

Background Whereas outdoor temperature is linked to both mortality and hydration status, the hormone vasopressin, measured through the surrogate copeptin, is a marker of cardiometabolic risk and hydration. We recently showed that copeptin has a seasonal pattern with higher plasma concentration in winter. Here, we aimed to investigate the as-sociation between outdoor temperature and copeptin.Methods Copeptin was analysed in fasting plasma from five cohorts in Malmu, Sweden (n = 26,753, 49.7% men, age 18-86 years). We utilized a multivariable adjusted non-linear spline model with four knots to investigate the association between short-term temperature (24 h mean apparent) and log copeptin z-score.Findings We found a distinct non-linear association between temperature and log copeptin z-score, with both moderately low and high temperatures linked to higher copeptin concentration (p < 0.0001). Between 0 C-degrees and nadir at the 75th temperature percentile (corresponding to 14.3 degrees C), log copeptin decreased 0.13 z-scores (95% CI 0.096; 0.16), which also inversely corresponded to the increase in z-score log copeptin between the nadir and 21.3 C-degrees. Interpretation The J-shaped association between short-term temperature and copeptin resembles the J-shaped association between temperature and mortality. Whereas the untangling of temperature from other seasonal effects on hydration warrants further study, moderately increased water intake constitutes a feasible intervention to lower vasopressin and might mitigate adverse health effects of both moderately cold and hot outdoor temperatures.Funding Swedish Research Council, A Wiberg, M Stephen, A Pahlsson, Crafoord and Swedish Heart-Lung Foun-dations, Swedish Society for Medical Research and Swedish Society of Medicine.