Moderately elevated ambient temperature is associated with mortality in dialysis patients, but not in transplant patients.

Background: In many parts of the world, heat waves have been associated with excess morbidity and mortality in the general population. Studies on the effects of high-temperature exposure in kidney transplantation are lacking and are scare in dialysis patients. The aim of this study was to investigate the association between high temperatures and mortality for chronic kidney disease (CKD) stage 5 patients treated with dialysis or with a kidney graft in France using various definition of elevated temperature. Methods: In this retrospective cohort study, the association between temperature indicators and mortality was analysed with Poisson models taking into account the trend over time and seasonality and possible confounding factors. Models were compared by their AIC. All patients treated with RRT between 2012 and 2022 in France were extracted from the national REIN registry. Various definitions of elevated temperatures were explored based on all temperature measured at one station per district per hour and per day, from June to September during the years 2012-2022 in Metropolitan France. Results: Between June and September, over the years 2012-2022, temperatures varied from 6.7 to 45.4°C. During this period, 20 174 deaths were recorded among 116 808 dialysis patients and 3340 among 64 531 transplanted patients. A maximum temperature >32.5°C was associated with mortality and an incidence ratio (IR) of 1.09 (1.04-1.15) in the dialysed population. No association was found among transplanted patients. Conclusions: Further analyses are needed to confirm these results and better understand the biological and clinical impact of heat intensity and the cumulative effect with other environmental factors such as air pollution. More detailed studies on reasons for hospitalizations and causes of death are also planned.