Kidney stones are associated with an increased risk of cardiovascular disease, including coronary heart disease (CHD) and stroke, according to a meta-analysis.

“Our study suggests that kidney stones might be an important contributor to the risk of vascular events; the potential mechanisms for the findings may be related to metabolic disturbances,” the researchers wrote in a report published online ahead of print in the American Journal of Kidney Diseases.

Researchers at the First Affiliated Hospital of Guangxi Medical University in Nanning, Guangxi Zhuang Autonomous Region, China, analyzed data from 49,597 patients with kidney stones and 3.5 million controls who were enrolled in 6 prospective cohort studies.

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The median duration of follow-up was 8.9 years. Pooled results showed kidney stones were associated with a 19% increased risk of CHD and a 40% increased risk of stroke compared with controls, investigators led by Xue Qin, MD, PhD, reported. Specifically, kidney stones are associated with a 29% increased risk for myocardial infarction (MI) and a 31% increased risk of coronary revascularization.

Female patients had a significant 49% increased risk for MI whereas male patients had a non-significant 15% increased risk. “The evidence for increased risk of MI in female but not male patients is suggestive but not conclusive,” the authors noted. “We cannot explicitly test for this difference using metaregression analysis to claim a definite conclusion because of the limited number of studies. In addition, the difference between male and female cohorts in our analyses was unexpected and difficult to explain.”

Previous studies have demonstrated an association between kidney stones and metabolic syndromes, such as obesity, insulin resistance, hyperglycemia, hypercholesterolemia, and hypertension, the investigators stated. “These abnormalities may contribute to a higher risk of uric acid and calcium stone formation.”

In their discussion of study strengths, the researchers noted their study is the first meta-analysis and systematic review of the relationship between kidney stones and risk of cardiovascular diseases.

In addition, their meta-analysis only included studies with a prospective cohort design, which should decrease selection and recall biases, they pointed out.

Study limitations included the use of observational studies, which precludes  drawing conclusions about causality. In addition, the researchers said they were unable to exclude residual confounding by imprecisely measured cardiovascular risk factors or unmeasured confounding factors.