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, researchers at UT Southwestern Medical Center and UT Dallas have found.
Dehydration is one of the risk factors linked to kidney-stone disease, and the paper suggests global warming will exacerbate this effect. The researchers predict that by 2050, higher temperatures will cause an additional 1.6 million to 2.2 million kidney-stone cases, representing up to a 30 percent growth in some areas.
"This study is one of the first examples of global warming causing a direct medical consequence for humans," said Dr. Margaret Pearle, professor of urology at UT Southwestern and senior author of the paper, which appears in today's issue of Proceedings of the National Academy of Sciences.
"There is a known geographic variation in stone disease that has been attributed to regional differences in temperature," said Dr. Pearle. "When people relocate from areas of moderate temperature to areas with warmer climates, a rapid increase in stone risk has been observed. This has been shown in military deployments to the Middle East for instance."
Kidney-stone disease, or nephrolithiasis, is a common ailment. Kidney stones, which are solid crystals that form from dissolved minerals in urine, can be caused by both environmental and metabolic problems. Low volume of urine directly increases stone risk by increasing the concentration of stone-forming salts. They can arise from either taking in too little fluid or losing too much through dehydration.
Kidney-stones are more common in the warmer parts of the U.S. The Southeast is known as the "kidney-stone belt" because of the high incidence of kidney stones in the population living in Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina and Tennessee.
To forecast climate change, Dr. Tom Brikowski, lead author of the study and associate professor of geosciences at UT Dallas, 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.