Mortality After Bariatric Surgery in Diabetes

Roux-en-Y gastric bypass (RYGB) surgery may improve cardiovascular and all-cause mortality, according to a Swedish study published in Lancet Diabetes and Endocrinology.¹

“[W]e have shown a more than 50% reduction in relative risks of cardiovascular death and death from any cause in less than 5 years in patients with type 2 diabetes who underwent RYGB compared with matched control patients who did not undergo bariatric surgery, providing support for the benefits of this surgical treatment in such patients,” wrote first author Bjorn Eliasson, MD, of the University of Gothenburg (Sweden), and colleagues.

The study is the first to look at mortality in patients with diabetes after bariatric surgery. Though a few past studies have suggested a link between gastric bypass surgery and improved mortality, such studies have not looked specifically at patients with type 2 diabetes (T2DM).

In the nationwide observational cohort study, researchers used data from the Scandinavian Obesity Surgery Registry to identify patients in Sweden who had undergone RYGB surgery between 2007 and 2014 (n=6132). The study looked only at RYGB because it was the main surgical technique for gastric bypass surgery used in Sweden during that time period.

Researchers then matched RYGB patients by age, sex, BMI, and year with control patients (n=6132) who had not undergone RYGB (identified in the National Diabetes Registry). They used the Swedish Cause of Death Register to identify cause of death. Researchers followed patients for a median of 3.5 years.

Analyses of relative risk were adjusted for baseline characteristics, risk factors, treatments, and socioeconomic factors.

Key results for RYBG patients vs controls showed:

• Diabetes remission (HbA1c <6.5%) 1 year post-surgery: 52% vs 29% (between group difference P<0.0001)

• Significant improvement in systolic and diastolic blood pressure, LDL and HDL (all P<0.001)

• Increased use of lipid lowering (P=0.06) and antihypertensive drugs (P=0.046)

• Overall mortality: 58% relative risk reduction (hazard ratio [HR] 0·42, 95% CI 0·30–0·57; P<0·0001)

• Risk of fatal or non-fatal myocardial infarction: 49% lower (HR 0·51, 0·29–0·91; P=0·021)

• Risk of cardiovascular death: 59% lower (0·41, 0·19–0·90; P=0·026)

• 5-year absolute risk of death: 1·8% (95% CI 1·5–2·2) with RYGB vs 5·8% (5·0–6·8)

The authors noted small but significant differences between the two groups. For example, the RYGB group had a history of fewer strokes and less congestive heart failure, and were more likely to be married, have higher income, and better educational level than the control group. Analyses excluding patients with these disorders, however, yielded similar results. In addition, the study matched patients by sex, age, and BMI between groups in order to minimize selection bias and the effect of unknown confounders.

“The causes of these beneficial effects could be the weight reduction per se, changes in physiology and metabolism, improved care and treatment, improvements in lifestyle and risk factors, or combinations of these factors,” the authors concluded.

Take-home Points

• Swedish study has shown 58% improvement in relative risk of overall mortality, 59% lower relative risk of CVD death in patients with T2DM who had RYGB compared to those who did not.

• Patients who had RYGB also had significant improvement in diabetes remission, systolic and diastolic blood pressure, LDL and HDL, and increased use of lipid lowering and antihypertensive drugs vs controls.

• Weight reduction, changes in physiology and metabolism, and improvements in care, treatment, lifestyle and risk factors, or combinations of these, could explain the results.

Reference: Eliasson B, et al. Cardiovascular disease and mortality in patients with type 2 diabetes after bariatric surgery in Sweden: a nationwide, matched, observational cohort study. Lancet Diabetes Endocrinol. 2015 Nov;3(11):847-854.