Global Warming May Up Kidney Stone Risk: Study

July 15, 2008— -- For four years, Sue May of Valdosta, Ga., lived with the pain of four minuscule fragments of stone-hard minerals in her kidney.

And according to May, now 64, an experience with kidney stones is just as painful as it sounds.

"You feel horrible," May says. "When you have this, it's a constant infection, and a lot of pain that goes along with it.

"Sometimes it felt like someone had drilled through my back and into my kidney."

May eventually underwent a 2½-hour procedure to rid herself of the stones. Today she feels much better -- but relief came at a price. The surgery alone cost $20,000.

Now, a study released Monday suggests that as global warming causes temperatures to rise, Americans living in certain areas of the country may suffer from as many as 30 percent more kidney stones by the year 2050 -- and treatment costs for the condition could spike by hundreds of millions of dollars each year.

The findings are published in the current issue of the Proceedings of the National Academy of Sciences.

"We're quite confident that kidney stone prevalence is related to climate," says lead study author Tom Brikowski, associate professor of geology at the University of Texas at Dallas.

"We're certain that warming will continue and we're certain that it's going to accelerate," he says. "We can certainly say that it's going to be a significant effect."

But some health and environment experts wonder whether the finding will be lost in the shuffle when compared with other, arguably more frightening aspects of global warming.

Does Kidney Stone Risk Rise With the Mercury?

Brikowski, whose wife is a veterinarian, says he first suspected that heat might be related to kidney stone formation after his wife noted an increase in kidney stones in the animals she treated during a long drought.

He says the spike in kidney stones reported in troops deployed to Middle Eastern deserts offered further evidence of the connection.

In his study, Brikowski says fluid loss through excess sweating explains the link between hot climate and kidney stones. More water loss through perspiration means more concentrated urine -- and more concentrated urine means a higher risk of kidney stones.

Of course, there are many reasons for kidney stones. As for May, her kidney stones were not caused by warm weather; they were the result of a heart catheter infection that had spread throughout her body, eventually infecting her kidneys and causing the stones to form.

Still, some researchers who study the potential health effects of global warming say the new research offers intriguing clues to yet another connection between climate change and human health.

"I have not seen any other studies before that looked specifically at kidney stones and climate change, but it is a finding that would be consistent with dehydration across the population if people were exposed more frequently to larger heat waves," says Dr. Jonathan Patz, a professor in the department of population health sciences and the Center for Sustainability and the Global Environment at the University of Wisconsin-Madison.

Public May Shrug Off the Stones

But considering the myriad of frightening predictions that accompany most any discussion on the impacts of global warming on human health -- from monster hurricanes to famine to the unchecked spread of infectious diseases -- kidney stones may seem somewhat tame.

"I don't think you can compare it to something globally like malaria, which kills 2 million people per year, most of whom are children," he says.

And he adds that singling out kidney stones as yet another consequence of global warming could be the wrong approach when it comes to communicating effectively with the public.

"When you focus on the health effects of climate change, it might be wrong to pick out single outcomes and be overly focused on those," he says.

It is a point with which Kristi Ebi agrees.

"The study is suggestive of the idea that kidney stones are a risk that people have not considered in the past," says Ebi, lead author for the Intergovernmental Panel on Climate Change Fourth Assessment Report and an independent consultant on the health effects of global climate change.

She says that she would have liked for the research to include some sense of whether these additional cases of kidney stones would be preventable.

"For a lot of health issues, at some point people just tune it out," Ebi says. "There seem to be these phases we go through. We hear that this causes cancer and that causes cancer. At one point, the public says 'everything causes cancer, and I'm not going to worry about it.' This is not effective risk communication."

Brikowski acknowledges that this research is still in its primary phases, and that the exact toll of global warming in the form of kidney stones begs for further elucidation.

Still, he notes, this connection may well just scratch the surface of many other human health effects brought about by widespread climate change. And with these new revelations, he says, health and climate experts will likely begin working more closely to assess these impacts.

"We're going to see more of these unusual collaborations," he says.

Lauren Cox and Lara Salahi contributed to this report.