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Bariatric surgery associated with substantially lower risk of death vs non-surgical treatment

Bariatric surgery for patients with T2DM and BMI>35 was associated with substantially lower risk of death across all important patient strata, compared with nonsurgical management, according to researchers from Canada. In addition, surgery was also associated with a lower risk of overall cardiac events and non-fatal renal outcomes. The findings were featured the paper, ‘Association Between Bariatric Surgery and Major Adverse Diabetes Outcomes in Patients With Diabetes and Obesity’, published in JAMA Network.

The researchers performed a multi-centre population-based cohort study that matched patients with obesity and T2DM who underwent bariatric surgery with a non-surgical control group. Using data from multiple linked administrative databases, they matched individuals on a comprehensive list of confounders to determine the association of bariatric surgery with mortality and complications of diabetes.

The main study outcome was all-cause mortality and the secondary outcomes included cause-specific mortality and several diabetes-relevant outcomes: a composite cardiovascular outcome (ie, cardiovascular mortality, nonfatal myocardial infarction, stroke, percutaneous coronary intervention, coronary artery bypass graft, transient ischemic stroke, deep vein thrombosis, or pulmonary embolism), a composite renal outcome (ie, new dialysis treatment or transplantation), and retinopathy.

In total, 3,455 surgical patients were matched with 3,455 controls with 4,950 female participants (71.6%) and the mean (SD) BMI was 44.67 (7.9). From the 3,455 patients who underwent bariatric surgery, 2,994 (86.7%) underwent a gastric bypass and 3,054 participants (44.2%) were diagnosed T2DM within five years of the index date and 712 participants (10.3%) had documented diabetes with microvascular or macrovascular complications.

In total, there were 261 deaths (3.7%) during a median follow-up of 4.6 (3.22-6.35) years - 83 deaths (2.4%) in the surgery group and 178 deaths (5.2%) in the control group. The absolute risk reduction (ARR) for mortality associated with bariatric surgery was 2.7% (95% CI, 1.9-3.6%), and the adjusted hazard ratio (HR) for the surgery group was 0.53 (95% CI, 0.41-0.69).

Gastric bypass patients had a 46% lower hazard of all-cause mortality compared with their matched counterparts (HR, 0.54 [95% CI, 0.40-0.71]). In addition, a similar association was observed in patients who received a sleeve gastrectomy. Overall, the observed associations of gastric bypass or sleeve gastrectomy with primary and secondary outcomes were similar.

Surgery was also associated with reduced absolute mortality risk across all diabetic disease length cohorts and relative benefits for those with less than 15 years of diabetes. The association was strongest in patients with disease duration of five years or less, with a 52% reduction in the hazard of mortality (HR, 0.48 [95% CI, 0.29-0.78]) and an ARR of 2.2% (95% CI, 1.0%-3.3%) at the end of follow-up.

“Our findings demonstrate that bariatric surgery was associated with preventing cardiac events in patients with diabetes and obesity, likely through the synergistic interactions of weight loss, glycaemic control, and other neurohumoral mechanisms for maintaining weight loss and glycaemic control,” the authors reported. “Furthermore, patients in our study who underwent bariatric surgery had lower risk of nonfatal renal outcomes, which suggests an association of bariatric surgery with limiting noncardiac diabetic outcomes.”

For patients with diabetes more than five years to ten years, bariatric surgery was associated with an ARR of 3.1% (95% CI, 1.4%-4.8%) and a decrease in hazard of all-cause mortality of 51% (HR, 0.49 [95% CI, 0.29-0.82]). Patients who had diabetes for longer than 15 years had an ARR of 4.3% (95% CI, 0.8%-7.8%), but the hazard of mortality was not statistically significantly reduced (HR, 0.66 [95% CI, 0.39-1.13]).

The benefit of bariatric surgery was strongest in patients aged 55 years or older, among whom there were 52 deaths (3.6%) in the surgical group compared with 121 deaths (8.3%) in matched controls. In this age group, hazard of all-cause mortality was reduced by 51%. For surgical patients aged 45 to 54 years, surgery was associated with an ARR of 1.8% (95% CI, 0.5%-3.0%) and multivariate analysis revealed a 44% reduction in hazard of all-cause mortality (HR, 0.56 [95% CI, 0.34-0.93]). This suggests that bariatric surgery should be aggressively recommended for patients within this population.

Patients with a BMI of 40 or greater experienced a mortality benefit with surgery. Multivariable analysis showed significant mortality benefit for patients with higher BMI, with a 52% reduction in all-cause mortality among those with a BMI of 40 to 50 and a 56% in those with a BMI of greater than 50. Patients with BMI less than 40 who underwent surgery had fewer deaths (27 deaths [3.3%] in the surgery group vs 39 deaths [4.7%] in the control group), but the difference was not significantly significant (p=0.35).

“Overall, this study reinforces that the glycaemic benefit of bariatric surgery found in randomised clinical trials likely translates to a mortality benefit over time, and it supports the use of surgery as a first-line treatment for individuals with obesity and diabetes,” they authors concluded.

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