Metformin continuation post-metabolic bariatric surgery and relapse of diabetes.

Aim: To evaluate the association of metformin continuation with relapse of diabetes after metabolic bariatric surgery (MBS) in patients with type 2 diabetes and obesity who achieved an HbA1c level of less than 6.5%.

Materials And Methods: This observational, retrospective cohort study included Clalit Health Service members aged 24 years or older with obesity and diabetes, who were treated with metformin, underwent MBS during 2005-2020 and achieved an HbA1c level of less than 6.5% up to 6 months after surgery (index date). Patients who continued metformin treatment (> 2 prescriptions filled, n = 122) after the index date were matched (1:2) on age, sex and HbA1c level at index date and compared with those who stopped treatment (no filled prescriptions, n = 244). The outcome was relapse of diabetes as measured by an HbA1c level of 6.5% or higher (yes/no).

Results: The two matched groups maintained a mean HbA1c level of less than 6.5% during the follow-up (mean ~ 5 years). An adjusted Cox proportional hazards model revealed no significant association of metformin continuation after MBS with relapse of diabetes (adjusted hazard ratio = 1.70, 95% confidence interval: 0.98-2.94). No significant differences were observed between the two groups in weight loss and filled prescriptions for other diabetes medications during the follow-up period.

Conclusions: Among individuals living with obesity and diabetes who achieved diabetes remission post-MBS, metformin continuation was not associated with relapse of diabetes. This lack of an association indicates that metformin did not provide an additional benefit for maintaining glycaemic control or weight reduction during an average of 5 years postsurgery.