Study Links Kidney Stones to Climate Change

Climate change is likely to cause a dramatic rise in kidney stone disease in the U.S. by 2050, according to a study to be published in the next issue of the Proceedings of the National Academy of Sciences (PNAS).

Tom Brikowski
Study Online: “Climate-related increase in the prevalence of urolithiasis”

The study, by researchers from UT Dallas and UT Southwestern Medical Center, is the first time scientists have been able to identify a direct impact of climate change on human health.

“The prevalence of kidney stones is likely to increase by 30 percent or more in some areas,” according to Dr. Tom Brikowski, the lead author of the study and an associate professor of geosciences in the UT Dallas School of Natural Sciences and Mathematics.

The researchers predicted approximately 2.2 million new climate-related cases of kidney stones by mid-century. The annual cost of treating these new cases will exceed $1 billion, an increase of 25 percent over current expenditures.

Currently, a belt of elevated risk of kidney stones is found in the southeastern U.S., and is associated primarily with high annual temperatures. “With warming, that belt will expand significantly northward and westward,” said Dr. Brikowski.

To forecast climate change, Brikowski used models of global warming obtained from the Intergovernmental Panel on Climate Change’s 2007 Fourth Assessment Report, in which predicted temperature increases are based on expectations of future greenhouse gases. Using two studies that reported kidney-stone rates in various geographic regions and correlating regional stone rates with local mean annual temperatures, Dr. Brikowski created a mathematical model relating temperature to kidney-stone risk. In combination with a previously existing model, the researchers were able to compare and contrast their findings.

High temperatures are often correlated with low urine volumes because of dehydration, which directly increases the risk of forming kidney stones. “If that increase is steady with temperature, high-population coastal regions like Texas, Florida and California would see the largest increases. If the risk climbs steeply at some threshold temperature, a band stretching from Kentucky to northern California would see the most new cases,” Brikowski said.

Co-author Dr. Yair Lotan, assistant professor of urology at UT Southwestern, used current cost of kidney stone treatment to estimate future climate-related cost increases. Dr. Margaret Pearle, professor of urology at UT Southwestern, also a co-author, analyzed current distribution of kidney stones.

Dr. Brikowski began working on this problem in 1999, after his wife, a veterinarian, noted an increase in animal kidney stones during drought years. Intrigued by this phenomenon, Dr. Brikowski, who is a hydrologist, tried to find a link between the stones and the drought conditions. Eventually, however, he determined that it was not drought, but heat, that was the cause. For further study, he contacted his two co-authors at the UT Southwestern Department of Urology.

Dr. Brikowski notes that this is a preliminary study that shows the effects of kidney stones from climate change will be significant, but that the exact details of the phenomenon are still unknown and further studies are needed.

The researchers plan to pursue further research to reduce these uncertainties and have applied for a grant from the National Institutes of Health. Those results will provide a crucial basis for adjustments in medical prevention and healthcare delivery in preparation for this projected onslaught of kidney stone disease.

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