Kidney Stone Disease Tied to Obesity

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Obesity is associated with an increased risk of kidney stone disease, researchers concluded.

Brian R. Matlaga, MD, and his colleagues at Johns Hopkins University School of Medicine in Baltimore, studied 95,598 patients, 54,572 female (57.1%) and 41,026 male 42.9%).

Among non-obese subjects (BMI less than 30 kg/m2), 2.6% were diagnosed with a kidney stone during the evaluation period (2002-2006), compared with 4.9% of obese patients (BMI of 30 or greater), according to a report in The Journal of Urology (2010;183:571-575). At all stratifications of obesity, except for men with a BMI greater than 50, obese patients were significantly more likely to be diagnosed with a kidney stone that non-obese patients.

Among male subjects, those with a BMI of 30-34.9, 35-39.9, 40-44.9, and 45-49.9 had a significant 2.44, 2.74, 2.66, and 3.18 times increased risk of kidney stone disease compared with individuals who had a BMI below 20.

Among female subjects, compared with those who had a BMI below 20, those with a BMI of 30-34.9, 35-39.9, 40-44.9, 45-49.9, and 50 or greater had a significant 1.95, 1.84, 2.42, 2.31, and 2.54 increased risk of kidney stone disease. Researchers observed no significantly increased risk among those with a BMI of 20-24.9.

“What the present work uniquely adds to our understanding of the relationship between obesity and kidney stone disease is the subcategorization of a large cohort with extreme, or morbid, obesity,” the authors wrote. They noted that their analysis included 33,051 subjects with a BMI greater than 30 and 11,413 subjects with a BMI greater than 35.

“Therefore, we can provide a robust description of the prevalence of stone disease among all categories of obesity,” they wrote. To their knowledge, they stated, no similar report has stratified the effect of increasing degrees of obesity on stone risk, especially in extremely obese patients.

“Obesity is associated with an increased risk of kidney stone formation, a concerning finding considering that obesity and nephrolithiasis are increasing at a great rate,” Dr. Matlaga's group concluded.

“However, the risk of stone disease in the obese population does remain stable with increasing degrees of obesity as stratified by BMI based on our present analysis. Dietary modification and weight loss should be encouraged in the obese population for a multitude of reasons but also to reduce stone risk.”

In a previous study published in the Journal of the American Medical Association (2005;293:455-462), researchers found that a BMI of 30 or greater was associated with a twofold increased risk of kidney stone formation in women and a 33% increased risk in men compared with a BMI of 21-22.9.

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