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Bariatric surgery reduces risk for microvascular complications in prediabetes, type 2 diabetes
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Patients with obesity and either prediabetes or type 2 diabetes saw a reduced, long-term risk for microvascular complications after undergoing bariatric surgery compared with similar patients who received usual care, according to findings in a Swedish study.
“Bariatric surgery prevents microvascular complications in obese patients with a glucose status ranging from normal to established type 2 diabetes, and the greatest [RR] reduction is obtained in those with prediabetes,” Lena M. S. Carlsson, MD, PhD, of the Institute of Medicine at Sahlgrenska Academy, University of Gothenburg, Sweden, told Endocrine Today. “In obese patients with prediabetes, bariatric surgery prevented microvascular complications in those that remained free from diabetes, indicating that long-term exposure to slightly elevated glucose levels (below the cutoff for diabetes) is harmful.”
Carlsson and colleagues analyzed data from 4,032 patients aged 37 to 60 years recruited for the nonrandomized Swedish Obese Subjects (SOS) study between September 1987 and January 2001. Included men had a BMI of at least 34 kg/m²; included women had a BMI of at least 38 kg/m². Patients were stratified by four groups: Normal glucose tolerance (fasting blood glucose concentration < 5 mmol/L); prediabetes (5-6 mmol/L); screen-detected type 2 diabetes (≥ 6.1 mmol/L without a previous diagnosis) and established type 2 diabetes diagnosed before study enrollment. Within the surgery group (n = 2,001), 265 patients underwent gastric bypass; 376 underwent gastric banding; 1,369 underwent vertical-banded gastroplasty. The control group (n = 2,031) received usual care. Participants provided fasting blood samples at baseline and follow-up at 2, 10 and 15 years; researchers assessed glucose, insulin, C-peptide, lipid and creatinine levels. Diabetes status was determined at 2-, 10- and 15-year exams. Microvascular events diagnosed during hospital stays or hospital-based outpatient care (diabetic retinopathy, diabetic kidney disease) were identified from the National Patient Register. Researchers used Kaplan-Meier estimates of cumulative incidence to analyze time-to-first microvascular event, and Cox proportional hazard models to estimate the difference between the surgery and control groups.
Within the cohort, 35 patients had a history of microvascular disease (19 in surgery group; 16 controls); average maximal weight loss ranged from 25 kg to 32 kg.
During follow-up, researchers observed 224 incidences of first microvascular disease in the surgery group (6.3 events per 1,000 person-years) and 374 in the control group (10.9 events per 1,000 person-years). Incident microvascular disease was lower in the surgery group vs. controls for all subgroups except those aged 47.8 to 53 years (P = .058).
Baseline glycemic status was the only significant interaction between treatment effect and baseline risk factors, according to the researchers (P for interaction = .0003). The lowest HR was observed for patients with prediabetes (HR = 0.18; 95% CI, 0.11-0.3), followed by those with screen-detected type 2 diabetes (HR = 0.39; 95% CI, 0.24-0.65), established diabetes (HR = 0.54; 95% CI, 0.4-0.72) and normal glucose tolerance (HR = 0.63; 95% CI, 0.48-0.81). Results persisted after adjustment for baseline age, sex, BMI, blood pressure, urinary albumin excretion and smoking status.
“Overall, one incidence of microvascular disease was prevented for every 22 patients who underwent surgery over 10 years,” the researchers wrote. “After stratification by glycemic status at baseline, the number needed to treat to prevent one incidence of microvascular disease was similar in subgroups with prediabetes (n = 7), screen-detected diabetes (n = 8) and established diabetes (n = 4), but higher in the subgroup with normal blood glucose concentration (n = 48).”
The most common observed microvascular complication was diabetic retinopathy, which was reduced after bariatric surgery across all glycemic subgroups, with unadjusted HRs ranging from 0.18 in those with prediabetes to 0.51 for those with established type 2 diabetes at baseline (P < .0001 for both). Among the 129 patients in the surgery group with type 2 diabetes at baseline, 39 were in remission after 15 years’ follow-up, the researchers noted.
“We need new, effective nonsurgical treatments for prediabetes,” Carlsson said. “Our research shows that prediabetes is a serious condition that should be treated, and that this can be done by bariatric surgery. However, it is not possible or desirable to operate all obese patients with prediabetes.” – by Regina Schaffer
For more information:
Lena M. S. Carlsson, MD, PhD, can be reached at the Sahlgrenska Academy at the University of Gothenburg, Box 100, S-405 30, Gothenburg, Sweden; email: lena.carlsson@medic.gu.se.
Disclosure: Carlsson reports receiving lecture fees from AstraZeneca, Johnson & Johnson and Merck, Sharp & Dohme; three researchers are employees of or hold stock in AstraZeneca. Please see the full study for the other authors’ relevant financial disclosures.
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