Type 2 diabetes after gastric bypass: remission in five models using HbA1c, fasting blood glucose, and medication status

Background: The remission rates of type 2 diabetes mellitus (T2DM) after Roux-en-Y gastric bypass (RYGB) vary according to the glycosylated hemoglobin A1c (HbA1c), fasting blood glucose (FG), and medication status. Our objectives were to describe remission using the American Diabetes Association standards for defining normoglycemia and to identify the factors related to the preoperative severity of T2DM that predict remission to normoglycemia, independent of weight loss, after RYGB. The setting was an urban not-for-profit community hospital.

Methods: We performed a retrospective analysis of prospectively collected data from a cohort of 2275 patients who qualified for bariatric surgery (2001-2008). Five different models for defining remission (no diabetes medication and a FG <100 mg/dL; no diabetes medication and HbA1c <6.0; no diabetes medication and HbA1c <5.7%; no diabetes medication, FG <100 mg/dL, and HbA1c <6.0%; and no diabetes medication, FG <100 mg/dL, and HbA1c <5.7%) were compared in 505 obese patients with T2DM 14 months after RYGB. The secondary aims were to determine the effects of preoperative insulin therapy and the duration of known T2DM on remission.

Results: Of the 505 patients, 43.2% achieved remission using the most stringent criteria (no diabetes medication, HbA1c <5.7%, and FG <100 mg/dL) compared with 59.4% using the most liberal definition (no diabetes medication and FG <100 mg/dL; P < .001). The remission rates were greater for patients not taking insulin preoperatively (53.8% versus 13.5%, P < .001) and for patients with a more recent preoperative T2DM diagnosis (8.9 versus 3.7 yr, P < .001).

Conclusion: Remission, defined at a threshold less than what would be expected to result in microvascular damage, was achieved in 43.2% of diabetic patients by 14 months after RYGB. A more recent diagnosis of T2DM and the absence of preoperative insulin therapy were significant predictors, regardless of how remission was defined, independent of the percentage of excess weight loss.