Association Between Bariatric Surgery and Major Adverse Diabetes Outcomes in Patients With Diabetes and Obesity | Bariatric Surgery | JAMA Network Open | JAMA Network
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    Original Investigation
    April 26, 2021

    Association Between Bariatric Surgery and Major Adverse Diabetes Outcomes in Patients With Diabetes and Obesity

    Author Affiliations
    • 1Division of General Surgery, McMaster University, Hamilton, Canada
    • 2ICES, Toronto, Canada
    • 3Institute of Health Policy, Management, and Evaluation, University of Toronto, Toronto, Canada
    • 4Population Health Research Institute, Hamilton, Canada
    • 5Department of Medicine, McMaster University, Hamilton, Canada
    • 6Department of Medicine, University of Toronto, Toronto, Canada
    • 7Sunnybrook Research Institute, Toronto, Canada
    • 8Programs for Assessment of Technology in Health Research Institute, St Joseph’s Healthcare, McMaster University, Hamilton, Canada
    • 9Department of Clinical Epidemiology and Biostatistics, Faculty of Health Sciences, McMaster University, Hamilton, Canada
    JAMA Netw Open. 2021;4(4):e216820. doi:10.1001/jamanetworkopen.2021.6820
    Key Points

    Question  Is there an association between bariatric surgery and all-cause mortality in patients with type 2 diabetes and severe obesity?

    Findings  In this cohort study that included 6910 patients with type 2 diabetes and severe obesity, there was a 47% decrease in all-cause mortality, a 68% decrease in cardiovascular mortality, and a 34% decrease in composite cardiac events associated with bariatric surgery compared with a nonsurgical control group after 4.6 years of follow-up. Patients who underwent surgery also had a 42% decrease in nonfatal renal events.

    Meaning  These findings suggest that bariatric surgery was associated with substantially lower all-cause mortality as well as nonfatal diabetic events in patients with type 2 diabetes.


    Importance  There are high-quality randomized clinical trial data demonstrating the effect of bariatric surgery on type 2 diabetes remission, but these studies are not powered to study mortality in this patient group. Large observational studies are warranted to study the association of bariatric surgery with mortality in patients with type 2 diabetes.

    Objective  To determine the association between bariatric surgery and all-cause mortality among patients with type 2 diabetes and severe obesity.

    Design, Setting, and Participants  This retrospective, population-based matched cohort study included patients with type 2 diabetes and body mass index (BMI; calculated as weight in kilograms divided by height in meters squared) 35 or greater who underwent bariatric surgery from January 2010 to December 2016 in Ontario, Canada. Multiple linked administrative databases were used to define confounders, including age, baseline BMI, sex, comorbidities, duration of diabetes diagnosis, health care utilization, socioeconomic status, smoking status, substance abuse, cancer screening, and psychiatric history. Potential controls were identified from a primary care electronic medical record database. Data were analyzed in 2020.

    Exposure  Bariatric surgery (gastric bypass and sleeve gastrectomy) and nonsurgical management of obesity provided by the primary care physician.

    Main Outcomes and Measures  The primary outcome was all-cause mortality. Secondary outcomes were cause-specific mortality and nonfatal morbidities. Groups were compared through a multivariable Cox proportional Hazards model.

    Results  A total of 6910 patients (mean [SD] age at baseline, 52.04 [9.45] years; 4950 [71.6%] women) were included, with 3455 patients who underwent bariatric surgery and 3455 match controls and a median (interquartile range) follow-up time of 4.6 (3.22-6.35) years. In the surgery group, 83 patients (2.4%) died, compared with 178 individuals (5.2%) in the control group (hazard ratio [HR] 0.53 [95% CI, 0.41-0.69]; P < .001). 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). Risk of nonfatal renal events was also 42% lower in the surgical group compared with the control group (HR, 0.58 [95% CI, 0.35-0.95], P = .03). Of the groups that had the highest absolute benefit associated with bariatric surgery, 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%).

    Conclusions and Relevance  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.