Bariatric Surgery Reduces Mortality for Type 2 Diabetes

Aristithes G. Doumouras, MD

While many studies have focused on how bariatric surgery impact type 2 diabetes patients, very few have focused solely on mortality in this patient population.

A team, led by Aristithes G. Doumouras, MD, MPH, Division of General Surgery, McMaster University, identified the association between bariatric surgery and all-cause mortality in patients with type 2 diabetes and severe obesity.

The Problem

“Global rates of obesity and type 2 diabetes are increasing together at a rapid pace, with the prevalence of obesity increasing 2-fold in 73 countries since 1980, and approximately 23% of individuals who are morbidly obese have diabetes,” the authors wrote. “Furthermore, obesity is associated with increased mortality with up to 20 years of life lost, and most obesity-associated mortality can be attributed to diabetes and cardiovascular causes.”

In the retrospective, population-based matched cohort study, the researchers examined 6910 type 2 diabetes patients with a body mass index (BMI) of 35 or greater who underwent bariatric surgery between 2010-2016 in Ontario. The mean age at baseline was 52.04 years old and 71.6% (n = 4950) of the patient population was women.

In addition, 3455 patients underwent bariatric surgery and 3455 matched control individuals. There was a median follow-up time of 4.6 years.

The Patients

The team used multiple linked administrative databases to define confounders, including age, baseline BMI, sex, comorbidities, durations of diabetes diagnosis, health care utilization, socioeconomic status, smoking status, substance abuse, cancer screening, and psychiatric history.

They identified potential controls from a primary care electronic medical record database.

The investigators sought a primary outcome of all-cause mortality, as well as secondary outcomes of cause-specific mortality and nonfatal morbidities.

Each group was compared through a multivariable Cox proportional Hazards model.

Mortality

In the surgery group, 2.4% (n = 83) patients died, while 5.2% (n = 178) participants in the control group died (HR, 0.53; 95% CI, 0.41-0.69; P <0.001).

However, a main finding shows bariatric surgery was associated with a 68% lower cardiovascular mortality (HR, 0.32; 95% CI, 0.15-0.66; P = .002) and a 34% lower rate of composite cardiac events (HR, 0.68; 95% CI, 0.55-0.85; P < .001 than the control group.

The researchers also found bariatric surgery resulted in a 42% lower risk of nonfatal renal events (HR, 0.58; 95% CI, 0.35-0.95; P = 0.03).

Men had an absolute risk reduction (ARR) of 3.7% 95% CI, 1.7%-5.7%), individuals with more than 15 years of diabetes had an ARR of 4.3% (95% CI, 0.8%-7.8%), and individuals aged 55 years or older had an ARR of 4.7% (95% CI, 3.0%-6.4%), leading the way as groups with the highest absolute benefit associated with bariatric surgery.

“These findings suggest that bariatric surgery was associated with reduced all-cause mortality and diabetes-specific cardiac and renal outcomes in patients with type 2 diabetes and severe obesity,” the authors wrote.

The study, “Association Between Bariatric Surgery and Major Adverse Diabetes Outcomes in Patients with Diabetes and Obesity,” was published online in JAMA Network Open.