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Fewer patients with type 2 diabetes who underwent bariatric surgery died in the years following surgery, according to a retrospective, population-based matched cohort study.

Bariatric surgery patients saw a 47% reduced risk of all-cause mortality in the median 4.6-year follow-up compared with matched controls who didn't undergo surgery (HR 0.53, 95% CI 0.41-0.69, P<0.001), reported Dennis Hong, MD, of St. Joseph's Healthcare in Ontario, Canada, and colleagues.

This equated to 83 deaths among the bariatric surgery group (2.4%) versus 178 deaths among matched controls (5.2%), they wrote in .

Overall, bariatric surgery was tied to an absolute risk reduction (ARR) for death of 2.7% (95% CI 1.9-3.6%).

However, certain patients tended to reap more benefits from the surgery, Hong's group found. Men saw an even greater reduction in all-cause mortality at an ARR of 3.7% (95% CI 1.7-5.7%) after surgery. Patients ages 55 and older had an ARR of 4.7% (95% CI 3.0-6.4%) tied to surgery, while patients who also lived with diabetes for over 15 years saw an ARR of 4.3% (95% CI 0.8-7.8%).

This mortality reduction was mainly driven by a significant drop in diabetes-related outcomes, such as cardiac and renal events, the authors reported. Specifically, these surgery patients saw a 68% reduced risk of cardiac death (HR 0.32, 95% CI 0.15-0.66, P=0.002), and a 32% (HR 0.68, 95% CI 0.55-0.85) lower rate for a composite of cardiac events: cardiovascular mortality, nonfatal MI, stroke, percutaneous coronary intervention, coronary artery bypass graft, transient ischemic stroke, deep vein thrombosis, and pulmonary embolism.

As for renal improvements, bariatric surgery patients saw a 42% (HR 0.58, 95% CI 0.35-0.95, P=0.03) lower risk of nonfatal renal events, which included the need for new dialysis treatment or kidney transplantation.

Cancer risk was also driven down following bariatric surgery, as these patients saw a 52% reduced risk for cancer-related death (HR 0.48, 95% CI 0.26-0.91).

However, there wasn't a significant benefit when it came to retinopathy risk (HR 0.81, 95% CI 0.55-1.19).

Of note, death due to trauma or suicide wasn't significantly different between surgery versus matched controls (HR 0.53, 95% CI 0.20-1.41).

Hong and colleagues stated that the "study reinforces that the glycemic benefit of bariatric surgery found in 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."

The study included a total of 6,910 patients from Ontario who underwent gastric bypass or sleeve gastrectomy. The majority of patients were women (72%) and the average age at the time of surgery was 52. They were matched with 3,455 control patients based on age, sex, BMI, and date of diabetes diagnosis.

All patients had pre-existing type 2 diabetes and a BMI over 35. Those with a BMI of 35 of less, over the age of 70, or had a history of several different predefined clinical conditions were excluded.

Although sleeve gastrectomy has gained popularity in the U.S. in recent years, Hong's group pointed out gastric bypass accounts for over 80% of all bariatric procedures performed in Ontario. In this particular study, 87% of surgery patients opted for gastric bypass.

"Sleeve gastrectomy is selectively performed for patients with BMI of 60 or greater as part of a 2-stage duodenal switch procedure or when a gastric bypass is contraindicated for medical (e.g., inflammatory bowel disease, need for certain medications) or surgical (e.g., small bowel disease or adhesions) reasons," they explained.

A study limitation was that "patients receiving bariatric surgery in Ontario undergo an extensive preoperative regimen of approximately 12 months. Therefore, patients who undergo surgery are likely to be more adherent to challenging postoperative lifestyle changes," according to the authors.

Hong's group suggested longer-term studies in younger patients with severe obesity, and in patients with lower BMI, such as class I obesity.

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