Extreme Humid-Heat Exposure and Mortality Among Patients Receiving Dialysis

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 characterized 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 US 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, 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 period of 3.6 years, 498,049 adults were exposed to at least 1 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% CI, 1.15-1.20]) during extreme humid-heat exposure. The 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.

Plain-Language Summary

Patients who receive dialysis are vulnerable to extreme weather events, and rising global temperatures may bring more frequent extreme heat events. We sought to determine whether extreme heat exposure was associated with an increased risk of death in urban-dwelling patients receiving dialysis across the United States. We found that people receiving dialysis were more likely to die during extreme humid-heat events, defined by a heat index exceeding 40.6°C (105°F) for ≥2 days or 46.1°C (115°F) for ≥1 day. These findings inform the nephrology community about the potential importance of protecting patients receiving maintenance dialysis from the risks associated with extreme heat.