Diurnal differences in the effects of heat exposure on renal function: A randomized controlled crossover trial.

Heat exposure causes distinct diurnal renal responses, with daytime exposure affecting blood markers and nighttime exposure elevating urinary stress biomarkers, highlighting time-dependent kidney vulnerability.

• Why it matters: Understanding how heat impacts kidney function at different times of day is crucial as climate change increases population exposure to nighttime heat, potentially heightening kidney injury risk.
• What they did: Forty-one healthy adults underwent controlled heat and thermoneutral exposures in a randomized crossover trial, with blood and urine samples analyzed for renal biomarkers before and after each session.
• The result: Daytime heat raised blood markers like creatinine and cystatin C, reducing glomerular filtration rate, while nighttime heat increased urinary biomarkers of early kidney stress, suggesting time-specific renal risks influenced by sleep and heart rate factors.