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BACKGROUND: People with obesity and type 2 diabetes (T2D) have reduced life expectancy, partly explained by increased risk of cardiovascular diseases and cancer. Here, we examined whether 2-year diabetes remission after bariatric surgery or usual care is associated with long-term mortality. MATERIALS AND METHODS: This report includes 586 participants with obesity and concomitant T2D from the prospective Swedish Obese Subjects (SOS) cohort study; 338 underwent bariatric surgery and 248 received usual obesity care. At inclusion, age was 37-60 years and BMI ≥34 kg/m2 in men and ≥38 kg/m2 in women. Median follow-up was 26.2 years (interquartile range 22.7-28.7). Diabetes status was determined using self-reported data on diabetes medication and in-study measures of blood glucose and HbA1c. The study was cross-linked to Swedish national registers for data on morbidity, death, and emigration. RESULTS: Overall, 284 participants, 71.9% of surgery and 16.5% of usual care patients, were in remission at the 2-year examination. During follow-up, mortality rates were 16.6 deaths per 1000 person-years (95% CI:13.7-20.1) in the remission subgroup and 26.0 deaths per 1000 person-years (95% CI:22.2-30.4) in the non-remission subgroup (adjusted hazard ratio (HRadj)=0.71, 95% CI:0.54-0.95, P=0.019). The adjusted median life expectancy in the remission subgroup was 2.5 years (95% CI:0.3-4.7) longer than in the non-remission subgroup. Specifically, remission was associated with decreased cardiovascular mortality (sub-HRadj=0.54, 95% CI:0.35-0.85, P=0.008), but no detectable association with cancer mortality was found (sub-HRadj=1.06, 95% CI:0.60-1.86), P=0.841). CONCLUSION: In this post-hoc analysis of data from the SOS study, patients who achieved short-term diabetes remission had increased life expectancy and decreased cardiovascular death over up to 32 years of follow-up. Future studies should confirm these findings.
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Importance: Obesity and insulin are risk factors for breast cancer, and retrospective studies suggest bariatric surgery reduces breast cancer risk in women. However, long-term prospective data on breast cancer risk after bariatric surgery and the role of baseline insulin levels are lacking. Objective: To examine if bariatric surgery is associated with breast cancer incidence in women and if treatment benefit is modified by baseline insulin levels. Design, Setting, and Participants: The Swedish Obese Subjects (SOS) study was a nonrandomized intervention trial designed to investigate the long-term effects of bariatric surgery on obesity-related mortality and morbidity. Study recruitment took place between 1987 and 2001, and median (IQR) follow-up time was 23.9 years (20.1-27.1) years. The study was conducted at 25 public surgical departments and 480 primary health care centers in Sweden and included 2867 women aged 37 to 60 years and with body mass index 38 or greater (calculated as weight in kilograms divided by height in meters squared). Intervention: In the surgery group (n = 1420), 260 women underwent gastric banding, 970 vertical banded gastroplasty, and 190 gastric bypass. The remaining contemporaneously matched control individuals (n = 1447) received usual obesity care. Main Outcome and Measures: Breast cancer, the main outcome of this secondary report, was not a predefined outcome in the SOS study. Breast cancer events were identified in the Swedish National Cancer Registry. Results: The study population comprised 2867 women with a mean (SD) age of 48.0 (6.2) years. During follow-up, there were 154 breast cancer events, 66 in the surgery group and 88 in the usual care group, and a decreased risk of breast cancer was observed in the bariatric surgery group (hazard ratio [HR], 0.68; 95% CI, 0.49-0.94; P = .019; adjusted HR, 0.72; 95% CI, 0.52-1.01; P = .06). The surgical treatment benefit on breast cancer risk was greater in women with baseline insulin levels above the median 15.8 µIU/L (HR, 0.48; 95% CI, 0.31-0.74; P = .001; adjusted HR, 0.55; 95% CI, 0.35-0.86; P = .008) compared to those below (HR, 0.95; 95% CI, 0.59-1.53; P = .84; adjusted HR, 1.01; 95% CI, 0.61-1.66; P = .97; interaction P = .02). Conclusions and Relevance: This prospective clinical trial indicated a reduced risk of breast cancer after bariatric surgery in women with obesity. The surgical treatment benefit was predominantly seen in women with hyperinsulinemia. Trial Registration: ClinicalTrials.gov Identifier: NCT01479452.