Patients whose diabetes improves after weight-loss surgery may also be less likely to suffer complications like eye and nerve damage, a U.S. study suggests.

Patients in the study had what's known as type 2 diabetes, in which sugar levels in the blood rise too high because the body can't use or make enough of the hormone insulin to convert food into energy.

After the weight-loss operations, some patients saw their diabetes go into remission, which can occur when blood sugar falls back to a healthy level. Patients who experienced remission were 29 percent less likely to develop complications of diabetes like eye, kidney and nerve damage than their peers who never had a remission, the study found.

For each year patients stayed in remission without a diabetes relapse, their risk of these complications was reduced by another 19 percent compared to their peers who never experienced remission, the study also found.

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"Even small periods of remission could lead to less disability later in life," lead study author Karen Coleman, a researcher at Kaiser Permanente in California, said by email.

To understand the connection between diabetes remission and eye, kidney and nerve damage, Coleman and colleagues analyzed data on 4,683 adults with diabetes who had bariatric surgery from 2001 to 2011.

At the start of the study, patients were 47 years old on average, and most were extremely obese. About 44 percent had unhealthy blood sugar levels, and more than 70 percent had other medical problems like high blood pressure or high cholesterol.

One year after surgery, 9.5 percent of the patients had damage to the small blood vessels in the eyes, kidneys and nerves of the hands and feet. By three years, this went up to 21 percent and at seven years it reached almost 41 percent.

Most of this so-called microvascular disease involved damage to the retina of the eye, which affected 37 percent of patients seven years after surgery.

Older patients were more likely to develop these complications after surgery than younger people, the study also found. People who had diabetes for a longer time prior to their operations were also more likely to have microvascular disease afterward than their peers who had not lived with diabetes for as many years before surgery.

Blood vessel damage tied to diabetes can lead to blindness, kidney failure, impotence and foot disorders that may eventually require amputations, Rachel Batterham, an obesity researcher at the University College of London who wasn't involved in the study, said by email.

Because the study was observational and everyone had weight-loss surgery, the results don't prove that bariatric procedures cause remission of diabetes, the authors note.

"Even a temporary remission is important as this study demonstrates that bariatric surgery can reset the clock in terms of reducing long-term microvascular disease secondary to diabetes," Dr. Manish Parikh, director of bariatric surgery at Bellevue Hospital Center in New York said by email. He wasn't involved in the study.

While it's possible some patients with diabetes might achieve remission without surgery, the study adds to evidence suggesting that bariatric procedures may offer patients some benefits beyond just weight loss, said Ted Adams, a researcher at Intermountain Healthcare and the University of Utah in Salt Lake City who wasn't involved in the study.

"Long-term risk reduction in eye, nerve and kidney complications shown in bariatric surgery patients even when their diabetes remission following surgery has been temporary may be explained at least in part by additional antidiabetic mechanisms beyond the effects of weight loss or reduction in food intake," Adams said by email.