Higher summer temperatures increase the likelihood of being hospitalized for acute renal failure (ARF), according to an analysis of data collected in New York State.

Overall, the odds of hospitalization for ARF increased 9% for each 5° F increment in temperature based on the mean temperature a day prior to hospitalization (lag 1). The risk was greater for blacks, Hispanics, individuals aged 25-44 years, and those in the lowest income quartile, the investigators, led by Shao Lin, MD, PhD, of the New York State Department of Health’s Center for Environmental Health in Troy, reported online ahead of print in the American Journal of Epidemiology.

Hispanics had a significant 20% increased risk per 5° F increment in temperature while compared with non-Hispanics (9%). Compared with whites (8%), blacks had a 14% increased risk for each 5° F, whereas Asians had a significant 12% decreased risk. Individuals aged 25-44 years had a significant 18% increased risk for each 5° F compared with those aged 45-64 years (9%). Individuals in the lowest income quartile ($31,406 per year or less) had a 13% increased odds of ARF hospitalization per 5° F compared with those in the highest quartile (more than $55,869 per year [7%]).

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The odds of an ARF hospitalization varied geographically within the state, with the largest associations observed in more urban regions.

Additionally, Dr. Lin’s group found increased odds of hospitalization for urinary tract infections, kidney stones, and other lower urinary tract disorders.

“Our findings add to a growing body of work that documents the association of high temperature and morbidity, particularly hospital admissions for renal diagnoses,” the authors concluded.

The investigators noted that most previous studies considered only heat waves, but their study is one of only a few to examine the effect of all summer temperatures on renal admissions.

They noted that their findings “can be useful in developing adaptation strategies and heat-warning policies.”

Dr. Lin’s team pointed out that the biologic mechanism underlying the relationship between heat and renal disease is unclear. Previous studies have found an increased incidence of renal calculi associated with exposure to hot conditions, presumably the result of disrupted fluid balance, the researchers explained.

In a discussion of study limitations, the investigators pointed out that they relied on ecologic-level exposure data. “Exposure temperature was assigned on the basis of residential address and took no account of personal activity,” they wrote. “Similarly, we do not know which individuals had access to air conditioning or other mitigation resources, another source of exposure misclassification.”