Global warming may increase incidence of stone disease

Global warming is likely to increase the proportion of the population affected by kidney stones by expanding the higher-risk region known as “the kidney-stone belt” into neighboring states, according to researchers at the University of Texas Southwestern Medical Center in Dallas.

Researchers predict that by 2050, higher temperatures will cause an additional 1.6 million to 2.2 million kidney stone cases, representing as much as 30% growth in some regions.

“This study is one of the first examples of global warming causing a direct medical consequence for humans,” said senior author Margaret Pearle, MD. “There is a known geographic variation in stone disease that has been attributed to regional differences in temperature. When people relocate from areas of moderate temperature to areas with warmer climates, a rapid increase in stone risk has been observed.”

The study was presented at the AUA annual meeting in Orlando, FL, and subsequently published in Proceedings of the National Academy of Sciences (2008; 105:9841-6).

Models of global warming were obtained from the Intergovernmental Panel on Climate Change’s 2007 Fourth Assessment Report, which predicted temperature on the basis of expected levels of future greenhouse gases. Using two studies that reported kidney stone rates in various geographic regions of the United States and correlating regional stone rates with local mean annual temperatures, the investigators were able to derive two mathematical models relating temperature to kidney stone risk.

Both models predicted that the current stone belt will expand with global warming, although the exact extent and location of the change were different in each model. One predicted that the increase will be concentrated in the southern half of the country; the other pointed to an increase in the upper Midwest. Taking into account the estimated future populations in those areas, increased temperatures are predicted to cause one million to two million more cases of kidney stone disease.

Dr. Pearle and colleagues plan to conduct future studies to understand the exact correlation of urine volume with environmental temperature.