Downgrading of type 2 diabetes mellitus (T2DM) after obesity surgery: duration and severity matter.

Background: There is overwhelming evidence for the antidiabetic effect of obesity surgery, but few reports involve objective longitudinal measurements of severity of type-2 diabetes mellitus (T2DM). This study applies a grading scheme and analyses the prognostic impact of routine clinical factors.
Material and Methods: This retrospective study includes 77 obese diabetic patients with a preoperative BMI of 48.9 ± 7.8 kg/m(2) who underwent gastric banding (n = 4), Roux-en-Y gastric bypass (n = 57), or sleeve gastrectomy (n = 16) between 2007 and 2013. A 6-point scoring system graded the level of antidiabetic therapy. Downgrading was calculated from the difference between pre- and postoperative grades.
Results: Downgrading reached its maximum at 3 months well before maximal weight loss: one grade in 6 (8 %) patients, two grades in 36 (47 %) patients, and three or more grades in 20 (26 %) patients. Age, gender, and preoperative weight had no impact on downgrading. There were no significant differences between gastric banding (median 1; 0-2), gastric bypass (median 2; 0-5), and sleeve gastrectomy (median 2; 0-4). Preoperative duration of T2DM and its severity grade were independent prognostic factors in multivariate analysis. The rate of patients who could discontinue insulin was more than 80 % when the duration of preexisting T2DM was less than 5 years as compared to 62 % when the duration was more than 5 years.
Conclusion: The severity of T2DM downgrades in most patients within the initial period of postoperative weight loss. Downgrading increases with shorter duration and lower severity grade of pre-existing T2DM.