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Kidney Stones Tied to Raised Heart Disease Risk in Women
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No such increased risk was seen among men with kidney stones, the researchers noted.
"A link between kidney stones and cardiovascular risk factors has been long suspected, however studies on the association with cardiovascular outcomes that take into consideration important aspects such as dietary factors or medications are lacking," said lead researcher Dr. Pietro Manuel Ferraro, a nephrologist at Columbus-Gemelli Hospital in Rome.
"Our study suggests that having kidney stones carries a higher risk of developing coronary disease in women independent of known cardiovascular risk factors such as diabetes or high blood pressure," he said.
However, why the risk is seen only among women is not clear, Ferraro noted.
"A possible explanation for the observed differences might be related to potential hormonal differences between men and women. Also, known differences in calcium metabolism between men and women might partly explain our findings," he suggested.
The report was published in the July 24/31 issue of the Journal of the American Medical Association.
Dr. Michael Palese, an associate professor of urology at the Icahn School of Medicine at Mount Sinai Medical Center in New York City, is not convinced that these findings are reliable.
"Previous studies have been inconsistent in evaluating the connection between kidney stones and heart disease," he said.
These data are "self-reported", so there is always a concern about the "inherent bias that comes with these kinds of studies," Palese added. "These findings should be taken with a grain of salt."
Another expert, Dr. Gregg Fonarow, a professor of cardiology at the University of California, Los Angeles, noted that a number of cardiovascular risk factors -- including diabetes, metabolic syndrome and high blood pressure -- are seen more often in men and women with kidney stones.
"While there are a number of potential mechanisms by which kidney stones could result in a higher risk for heart disease, it is not clear why these mechanisms would be only operative in women as suggested by this new study," Fonarow said.
To see what role kidney stones played in the risk for heart disease, Ferraro's team collected data on nearly 46,000 men who took part in the Health Professionals Follow-up Study and almost 200,000 women who were part of the Nurses' Health Study.
Among the more than 240,000 participants, nearly 20,000 reported a history of kidney stones. During 24 years of follow-up in men and 18 years of follow-up in women, nearly 17,000 developed heart disease, the researchers found.
Analysis showed that women with a history of kidney stones were about 30 percent more likely to develop heart disease, have a heart attack or undergo a procedure to open blocked heart arteries than men.
However, the connection between having kidney stones and developing heart disease was insignificant among men.
Kidney stones are a common problem. Recent data from the U.S. National Health and Nutrition Examination Survey found the prevalence of kidney stones to be an estimated 10.6 percent in men and 7.1 percent in women.
Overall prevalence increased from 3.8 percent in 1980 to 8.8 percent in 2010, Ferraro noted.
Another expert, Dr. Zeph Okeke, director of endourology at North Shore-LIJ's Arthur Smith Institute for Urology in Lake Success, N.Y., said the risks for kidney stones and heart disease are similar.
"Obesity, abdominal obesity or waist circumference [and body mass index] are associated with increased risk of kidney stone formation. This ties into the risk of heart disease since it is influenced by the same risk factors," Okeke said.
According to the U.S. National Institute of Diabetes and Digestive and Kidney Diseases, the best way to prevent kidney stones is to drink plenty of fluids, and to limit salt and protein from eggs, fish and meats.
SOURCES: Pietro Manuel Ferraro, M.D., nephrologist, Columbus-Gemelli Hospital, Rome, Italy; Michael Palese, M.D., associate professor, urology, Icahn School of Medicine, Mount Sinai Medical Center, New York City; Zeph Okeke, M.D., director, endourology, North Shore-LIJ Arthur Smith Institute for Urology, Lake Success, N.Y.; Gregg Fonarow, M.D., professor, cardiology, University of California, Los Angeles, and spokesman, American Heart Association; July 24/31, 2013, Journal of the American Medical Association