Incidence of type 2 diabetes after gastric by-pass surgery in a Swedish controlled cohort study

Abstract

Abstract Aims To assess the long-term risk of developing type 2 diabetes in patients with obesity who have undergone gastric bypass surgery compared to non-operated patients with obesity and the general population. Methods and results This study included 55,534 patients aged 20–65 years with a principal diagnosis of obesity in the Swedish Patient Register in 2001–2013. Of these, 23,099 had undergone gastric bypass and 32,435 had not. Each patient was matched by age, sex and geographic region with two population controls from the general population without an obesity diagnosis, i.e., 44,735 controls for the gastric bypass patients and 62,522 controls for the non-operated cohort with obesity. During a median follow-up of 4.2 years (interquartile range [IQR] 2.4, 7.1 years), 3,761 (11.6%) non-operated patients with obesity developed type 2 diabetes (incidence rate 226.0 per 1,000 person-years, confidence interval [CI] 218.8–233.4) compared to 381 (1.6%) among gastric bypass patients (incidence rate 38.7 per 1,000 person-years CI 34.7–43.5). The latter incidence was comparable to population controls incidence rate (34.7 per 1,000 person-years CI 31.7–38.2). Operated and non-operated patients with obesity were also directly compared using Cox regression analysis with adjustment for age, education, and sex, and showed gastric bypass patients had an 85% lower risk of developing diabetes compared to non-operated patients with obesity during the first six years of follow-up (hazard ratio 0.14; 95% CI 0.12–0.17). Conclusion Gastric bypass surgery for obesity seems to reduce the risk of developing type 2 diabetes to levels similar to that of the general population during the first six years of follow-up, but not thereafter. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Swedish government and the county councils concerning economic support of research and education of doctorsSwedish Heart and Lung FoundationSwedish Research Council