Heat and risk of acute kidney injury: An hourly-level case-crossover study in queensland, Australia

Background: The effects of hourly differences in temperature on the risk of acute kidney injury have not been investigated so far. This study aimed to examine a very short-term effect of heat on the risk of acute kidney injury at an hourly level and assessed potential modification effects by age, gender and preexisting diseases. Methods: We performed a time-stratified case-crossover design with a conditional logistic regression model to examine the association between hourly temperature and hourly emergency department visits for acute kidney injury (N = 1815) in Queensland state of Australia, 2013-2015. Heat effect on acute kidney injury was reported for temperature increases from 50th percentile (26.1 degrees C) to 95th percentile (33.6 degrees C). Results: The effect of heat on acute kidney injury occurred in the same hour of heat exposure (odds ratio (OR): 1.37; 95% confidence interval (CI): 1.10, 1.71), with no temperature threshold observed. Males (OR: 2.48; 95% CI: 1.85, 3.32) and those aged > 64 years (OR: 2.93; 95% CI: 2.01, 4.27), particularly those with pre-existing diabetes (OR: 2.51; 95% CI: 1.91, 3.30), hypertension (OR: 2.25; 95% CI: 1.61, 3.15), heart failure (OR: 2.21; 95% CI: 1.72, 2.84), or chronic kidney disease (OR: 2.59; 95% CI: 1.89, 3.55), were at great risks of acute kidney injury attack after exposure to heat. Conclusions: General practitioners and specialists should remind their patients about this risk in summer. Tailored heat adaptation strategies protecting adults working outdoors are urgently needed, especially within the context of climate change.