WEDNESDAY, Dec. 6 (HealthDay News) -- For people with type 1 diabetes, obesity is also associated with an increased risk of kidney disease, a U.S. study finds.

"Our results suggest that weight control is important in type 1 diabetes and that overweight patients with type 1 diabetes may need further evaluation and treatment," study lead author Dr. Ian H. de Boer, of the University of Washington in Seattle, said in a prepared statement.

Type 1 diabetes is the inherited form of the disease, in which the body fails to produce enough insulin. It differs from adult-onset type 2 diabetes, which comprises 95 percent of diabetes cases and is often linked to obesity.

In the study, de Boer and colleagues analyzed data on about 1,300 type 1 diabetes patients. These patients were part of a large study that found that intensive insulin therapy -- keeping blood sugar levels as close to normal as possible -- reduced the risk of kidney disease and other diabetes-related complications.

In this new study, the researchers looked at what effect obesity -- specifically waist circumference (central obesity) -- had on kidney disease risk.

Over an average of nearly six years of follow-up, 8.4 percent of the patients developed microalbuminuria -- small amounts of the protein albumin in urine. This is the first sign of diabetic kidney disease. The risk of microalbuminuria was 4.5 percent for patients who received intensive insulin therapy and 12.8 percent for those who received standard insulin treatment.

This study found that the larger a patient's waist measurement, the greater their risk for kidney disease. For each four-inch increase in waist circumference, there was a 34 percent increased risk of microalbuminuria. This held true even after the researchers adjusted for other factors, including intensive insulin therapy.

The findings were published online Wednesday by the Journal of the American Society of Nephrology, and are expected to be in the January print issue.

"Obesity is a growing problem for people with type 1 diabetes, but little was previously known about whether it affects risk for kidney disease in this group," de Boer said.

"Our research shows that central obesity is associated with an increased risk of developing microalbuminuria, which is not only an important sign of kidney disease but also a marker of increased risk for cardiovascular disease," he said.

More information

The National Kidney Foundation has more about diabetes and kidney disease.