ESRD: Extreme Heat Tied to Risk for Hospitalization, Death

Dana Najjar

August 09, 2019

Even a single day of extreme heat is associated with an increased risk for same-day hospital admission and same-day mortality in patients with end-stage renal disease (ESRD), new research suggests.

Climate change is a well-known risk factor for a variety of conditions, but little attention has been paid to the specific impact of extremely hot temperatures on vulnerable populations like patients with ESRD.

"A lot of the work that's been done with respect to heat-related epidemiology is focused on the general population," said Richard Remigio, a doctoral student at the University of Maryland and first author of an article published online today in JAMA Network Open. "With this work we were able to hone in on an already-established vulnerable population."

Extreme heat events were associated with a 27% increase in the rate of same-day hospital admission (95% confidence interval [CI], 1.13 - 1.43) and a 31% increase in the rate of same-day mortality (95% CI, 1.01 - 1.70) among patients with ESRD.

Preexisting comorbidities increased the risk for same-day mortality even more. Specifically, having both ESRD and diabetes was associated with an 83% increase in the rate of death, whereas ESRD with chronic obstructive pulmonary disease or congestive heart failure was associated with a 60% or 55% increase, respectively.

The researchers used electronic health record data from 7445 patients with ESRD who underwent hemodialysis treatments at one of three Fresenius Kidney Care centers in Boston, Philadelphia, and New York between 2001 and 2012.

The authors defined extreme heat events as days that exceeded the 95th percentile of heat for each calendar day and location, based on historical meteorological data. As is the case with most studies on the health effects of climate change, the researchers did not have access to the ambient temperature conditions for each participant: "We had to assume outdoor conditions matched indoor conditions," Remigio told Medscape Medical News. "That was a major limitation."

Overall, the observed effect was most pronounced for non-Hispanic black and white populations. No consistent effect was observed among Asian and Hispanic populations.

"The key findings are the geographic variability as far as the experience of hospitalization and mortality," Remigio said, "as well as the impact of comorbidity, race, and ethnicity." Those findings suggest that social determinants and the built environment could play an important role in the perceived intensity of the heat and its impact on hospitalization and mortality. Populations without access to air conditioners or cooling facilities may be especially vulnerable.

The findings are "not unexpected to those of us who are aware of the impacts of heat," Richard Johnson, MD, a nephrologist at the University of Colorado Hospital in Aurora, told Medscape Medical News.

"But it may catch you by surprise that there's such a pronounced effect of heat on mortality and admissions for our dialysis patients. It's really a statement of vulnerable populations being at increased risk," continued Johnson, who was not involved with the study.

Others agree. "Having a better understanding about the localized health risks and how risks do not apply universally across the country is quite illuminating in terms of understanding our preparedness and outreach to those who have pre-existing conditions," Vijay Limaye, PhD, climate change and health science fellow at the Natural Resources Defense Council, told Medscape Medical News. "A one-size fits all public health approach won't achieve the same benefits as a tailored approach."

Extreme heat has also been associated with kidney failure in young men who work long hours outside, killing an estimated 50,000 people worldwide already.

Any path to addressing the health effects of climate change will have to consider the extreme variability in risk between the general population and vulnerable groups, as well as the effects of geography, race, and socioeconomic status. End-stage renal disease disproportionately affects black and low-income populations, leaving them especially at risk during extreme heat events. Low-income populations are also less likely to have health insurance, which makes the cost of hospitalization staggering.

"We hear a lot about the cost of addressing climate change, but a lot less about the costs we are already paying," Limaye said. "Costs that are being borne and shouldered by our most vulnerable neighbors right now."

"It's time for physicians to really become aware of the health issues climate change is having on our population," Johnson said. "It isn't just something that we talk about as a future problem. It's actually occurring now."

The authors and interviewees have disclosed no relevant financial relationships.

JAMA Network Open. Published online August 9, 2019. Full text

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