Extreme Humid-Heat Exposure and Mortality Among Patients Receiving Dialysis

Am J Kidney Dis. 2024 Jun 12:S0272-6386(24)00808-4. doi: 10.1053/j.ajkd.2024.04.010. Online ahead of print.

Abstract

Rationale & objective: Exposure to extreme heat events has been linked to increased morbidity and mortality in the general population. Patients receiving maintenance dialysis may be vulnerable to greater risks from these events, but this is not well understood. We sought to characterize the association of extreme heat events and the risk of death among patients receiving dialysis in the United States.

Study design: Retrospective cohort study.

Setting & participants: Data from the United States Renal Data System were used to identify adults living in US urban settlements prone to extreme heat who initiated maintenance dialysis between 1997 and 2016.

Exposure: An extreme heat event was defined as a time-updated heat index (a humid-heat metric) exceeding 40.6°C for ≥2 days or 46.1°C for ≥1 day.

Outcome: Death.

Analytical approach: Cox proportional hazards regression to estimate the elevation in risk of death during a humid-heat event adjusted for age, sex, year of dialysis initiation, dialysis modality, poverty level, and climate region. Interactions between humid-heat and these same factors were explored.

Results: Among 945,251 adults in 245 urban settlements, the mean age was 63 years and 44% were female. During a median follow-up of 3.6 years, 498,049 adults were exposed to at least one of 7,154 extreme humid-heat events, and 500,025 deaths occurred. In adjusted models, there was an increased risk of death (hazard ratio 1.18; 95% confidence interval 1.15-1.20) during extreme humid-heat exposure. Relative mortality risk was higher among patients living in the Southeast (P<0.001) compared with the Southwest.

Limitations: Possibility of exposure misclassification, did not account for land use and air pollution co-exposures.

Conclusions: This study suggests that patients receiving dialysis face an increased risk of death during extreme humid-heat exposure.

Keywords: Heat; dialysis; extreme weather; humid-heat; mortality.