Long-term Incidence of Microvascular Disease after Bariatric Surgery or Usual Care in Patients with Obesity Stratified by Baseline Glucose Status

BACKGROUND: Bariatric surgery in patients with obesity and type 2 diabetes is associated with diabetes remission and prevention of complications. The long-term effects of bariatric surgery on microvascular complications in patients with prediabetes are unknown. METHODS: The prospective, matched Swedish Obese Subjects study examines outcomes after bariatric surgery. Patients were recruited between September 1, 1987, and January 31, 2001. Age was 37–60 years and BMI was ≥34 kg/m(2) in men and ≥38 kg/m(2) in women. The surgery group (n=2010) underwent gastric bypass (13·2%), banding (18·7%), or vertical banded gastroplasty (68·1%), and controls (n=2037) received usual care. After exclusion of 4 patients with suspected type 1 diabetes, and 11 patients with unknown glucose status at baseline, 4032 of the 4047 participants in the SOS study were included in the current analysis. The main outcome of this report was incidence of microvascular events (retinopathy, diabetic kidney disease, and neuropathy, whichever came first), obtained from nationwide registers, in subgroups stratified by baseline glucose status (euglycemia n=2838; prediabetes n=591; screen-detected diabetes n=246; established diabetes n=357). Data were analyzed both by intention to treat and per protocol. Median follow-up was 19 years. This study is registered with ClinicalTrials.gov, NCT01479452. FINDINGS: There were 374 first-time microvascular events in the control group and 224 in the surgery group (hazard ratio, 0·56; 95% CI 0·48–0·66; p<0·0001). There was a significant interaction between baseline glucose status and treatment effect (p=0.0003), and unadjusted hazard ratios for comparing the surgery group to the control group were lowest in the subgroup with prediabetes (0·18; 95% CI 0·11–0·30), followed by subgroups with screen-detected diabetes (0·39; 95% CI 0·24–0·65), established diabetes (0·54; 95% CI 0·40–0·72), and euglycemia (0·63; 95% CI 0·48–0·81). In patients with baseline prediabetes, treatment was associated with reduced incidence of microvascular events both in those who developed diabetes and in those who remained diabetes free during follow-up. INTERPRETATION: Bariatric surgery was associated with reduced risk of microvascular complications in all subgroups, but the greatest relative risk reduction was observed in patients with baseline prediabetes. Our results indicate that prediabetes should be treated aggressively to prevent future microvascular events.