Authors of a new study say their findings suggest bariatric surgery should be considered first-line treatment for the management of obesity in patients with type 2 diabetes.
Bariatric surgery was associated with a significant reduction in all-cause mortality as well as in nonfatal diabetes-specific events in patients with type 2 diabetes (T2D) and severe obesity, according to authors of a retrospective study published online April 26, 2021, in JAMA Network Open.
Specifically, the population-based study of nearly 7000 Canadian patients with T2D found that among those who underwent bariatric surgery there was a 47% decrease in all-cause mortality, a 68% decrease in cardiovascular (CV) mortality, and a 34% decrease in cardiac events.
“Overall, this study reinforces that the glycemic benefit of bariatric surgery found in randomized 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,” wrote investigators.
The investigative team, Led by Dennis Hong, MD, of the Division of General Surgery, St Joseph’s Healthcare, set out to bridge gaps in previous studies of the impact of bariatric surgery on mortality and long-term CV outcomes by using within-strata information on the association of surgery with mortality and controlling for a large number of potential confounding variables.
Participants in the matched-cohort study were drawn from multiple linked administrative databases in the Ontario Bariatric Network that included patients with diabetes who were eligible for bariatric surgery within a primary care practice and received bariatric surgery or routine nonsurgical care for diabetes and obesity from January 2010 through December 2016.
Of more than 27 000 patients who underwent bariatric surgery during the study period, 5986 were potentially eligible. The final surgical cohort of 3455 patients was matched to a nonsurgical cohort of 3455 patients using propensity score methods augmented with hard-matching based on age, sex, index BMI, and date of diabetes diagnosis.
All patients were classified as having severe obesity, ie, BMI ≥35 kg/m2.
Mean (SD) age of the entire cohort was 52.04 (9.45) years, 71.6% were women, and mean (SD) BMI was 44.67 (7.9). Among patients in the surgical group, gastric bypass was the most common bariatric procedure (86.7%). Diabetes was diagnosed in 44.2% within 5 years of the index date.
The primary study outcome was all-cause mortality. Secondary outcomes included cause-specific mortality (CV, oncologic, other medical) and diabetes-related outcomes (composite CV and composite renal outcomes).
Study authors controlled for potential confounding by age, baseline BMI, sex, comorbidities, duration of diabetes diagnosis, health care utilization, socioeconomic status, smoking status, substance abuse, cancer screening, and psychiatric history.
During a median follow-up period of 4.6 years, there were 83 (2.4%) deaths among surgical patients compared to 178 patients (5.2%) in the control group (HR, 0.53; 95% CI, 0.41-0.69; P <.001).
Compared to nonsurgical management, bariatric surgery was associated with a 68% reduction in risk of cardiovascular mortality (HR, 0.32; 95% CI, 0.15-0.66; P=.002) and a 32% lower risk of the composite cardiovascular outcome (HR, 0.68; 95% CI,0.55-0.85; P <.001).
Undergoing bariatric surgery also was associated with a 42% reduction in risk of the composite renal outcome (HR, 0.58; 95% CI, 0.35-0.95).
Further analysis identified multiple subgroups that appeared to have the greatest absolute benefit from bariatric surgery. The greatest benefit for mortality was seen among men (absolute risk reduction [ARR], 3.7%; 95% CI, 1.7-5.7%), those with a duration of diabetes greater than 15 years (ARR, 4.3%; 95% CI, 0.8-7.8%), and those 55 years of age or older (ARR, 4.7%; 95% CI, 3.0-6.4%).
The authors note that surgery was associated with mortality benefits in most strata of patients with diabetes. “These results support current guidelines that bariatric surgery should be a first-line therapy for patients with diabetes and severe obesity,” they wrote.
Study limitations noted are related primarily to the potential for residual confounding by unmeasured factors, the possibility of overfitting and collinearity within the statistical model, and the potential effects on the outcome of extensive presurgical preparation for bariatric patients in Ontario.