CHICAGO, Jan. 2 (Xinhua) -- Kidney disease increases the risk for diabetes, not just the other way around, a study of the Washington University at St. Louis has found.

Researchers at the university found that kidney dysfunction can lead to diabetes, and that a waste product called urea plays a role in the two-way link between the two diseases.

The study involved the analysis of medical records over a five-year period for 1.3 million adults who did not have diabetes. About 9 percent had elevated urea levels, a sign of reduced kidney function. That's the same rate as in the general population.

People with high urea levels were 23 percent more likely to develop diabetes than those with normal urea levels, the study found.

"The risk difference between high and low levels is 688 cases of diabetes per 100,000 people each year, which means that for every 100,000 people, there would be 688 more cases of diabetes each year in those with higher urea levels," said study senior author Ziyad Al-Aly, an assistant professor of medicine at Washington University School of Medicine in St. Louis.

"We have known for a long time that diabetes is a major risk factor for kidney disease, but now we have a better understanding that kidney disease, through elevated levels of urea, also raises the risk of diabetes," Al-Aly said.

"When urea builds up in the blood because of kidney dysfunction, increased insulin resistance and impaired insulin secretion often result," he said.

The findings about the role of urea may help improve treatment and possibly prevent diabetes. The study has been published online in the journal Kidney International.