To Örebro University

Background and aims: Bariatric surgery (BS) is an effective treatment for long-term weight loss in people with type 2 diabetes (T2D) and obesity. However, long-term prospective data on the efficacy and safety of BS with roux-en-y gastric bypass or sleeve gastrectomy in T2D populations are limited. AIMS: Evaluate the long-term effects of BS in people with T2D up to 14 years after surgery.

Materials and methods: A nationwide, matched, longitudinal, retrospective study based on data from the Swedish National Diabetes Registry (NDR) and the Swedish Obesity Surgery Registry (SOReg). Both registries cover more than 95% of all individuals with T2D and bariatric surgeries, respectively. A cohort of 8399 individuals with T2D (SOReg) who had undergone BS between 2007 and 2020 was matched by sex, age and BMI, with a control group from NDR who had not had surgery (n=8399). This study assessed the 28-day mortality rate after a CVD event, the long-term incidence of heart and kidney failure, psychiatric disorders and nutritional deficiencies. Data on outcomes were collected as ICD codes from the Swedish National Patient Registry and the Cause of Death Registry. Risks were quantified using unadjusted Cox regression models, yielding HR with 95% CI.

Results: In total, 16798 individuals with overweight or obesity were included and followed for up to 14 years. The mean BMI at the start of follow-up was 41±6 kg/m 2 , with a mean age of 49±10 years for both groups. The mean duration of T2D at baseline was 6.1 years for the control group and 6.5 years for the surgery group. The surgical group had slightly higher HbA1 c levels and education, but were less often single and had lower nicotine use (standardised mean difference, SMD >0.1). No significant differences were observed in cholesterol, eGFR, the prevalence of CVD, heart and kidney failure, psychiatric disorders, or nutritional deficiencies at baseline (SMD<0.1). During follow-up, the risk of heart failure, kidney failure, and death within 28 days of a CVD event was up to 45% lower in the surgically treated group compared to the controls (p <0.0001). However, the risk of hospitalisation for psychiatric disorders was increased after surgery (HR 1.21; 95% CI 1.13-1.29; p<0.0001). The surgically treated individuals also had a twofold increased risk of developing nutritional deficiencies compared to controls (HR 2.06; CI 1.84-2.31; p<0.0001) during the follow-up period.

Conclusion: This nationwide study shows that the benefits of bariatric surgery on CVD death, and heart and kidney failure for people with T2D are maintained in the long term. However, surgery increases the risk of suffering from psychiatric disorders or nutritional deficiencies for these individuals.