Bariatric surgery has had a beneficial effect on glycemic control in patients with type 2 diabetes, but not all patients achieve diabetes remission, and not all who do remain in remission.

Researchers at three large U.S. health care systems examined the effects of Roux-en-Y gastric bypass (RYGB) on diabetes remission and relapse in 4,434 adults with uncontrolled or medication-controlled type 2 diabetes mellitus (patients diagnosed only with gestational diabetes were excluded).

Complete remission was defined as discontinuation of diabetes medication plus fasting glucose values below 100 mg/dL or a glycated hemoglobin (HbA_1c) level less than 6%, or both, for 90 days or longer after the last dose of diabetes medication; partial remission was defined as discontinuation of diabetes medication and fasting glucose values below 126 mg/dL or HbA1c levels less than 6.5%, or both, for 90 days or longer after the last dose of diabetes medication.

Most patients (77%) were women; the average age was 50 years. At the time of surgery, a large percentage of patients (77%) were taking oral diabetes medication, insulin, or both. At one, three, and five years after surgery, 47%, 72%, and 77% of patients, respectively, had achieved partial diabetes remission or better, and 37%, 63%, and 68% of patients, respectively, had achieved complete remission. The median time to partial remission was 389 days; the median time to complete remission was 537 days.

Remission. Women were significantly less likely to achieve remission than men. Other factors decreasing the likelihood of remission were HbA_1c levels of 6.5% or more, a longer duration of diabetes, and treatment with insulin or oral diabetes medication before surgery.

Relapse. Relapse in the 2,254 patients who achieved complete remission occurred in 8%, 22%, and 35% of patients within one, three, and five years of remission, respectively, with a median time to relapse of eight years. Factors associated with a greater risk of relapse included older age, HbA_1c levels of 6.5% or more, a longer duration of diabetes, and receiving insulin before surgery. Relapse rates after partial remission at one, three, and five years occurred in 13%, 28%, and 40% of patients, respectively; the median time to relapse was seven years.

The authors conclude that when the primary goal of surgery is sustained diabetes remission, bariatric surgery early in the course of the disease is more effective. They also stress the importance of patient counseling for those aiming to achieve remission through surgery, noting that despite the risks of incomplete or failed diabetes remission and of diabetes relapse, "the remission rates achieved with RYGB appear to be far better than what could be achieved by any other behavioral or drug treatment."

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