Association Between Bariatric Surgery and Macrovascular Disease Outcomes in Patients With Type 2 Diabetes and Severe Obesity

Abstract

Importance: Macrovascular disease is a leading cause of morbidity and mortality for patients with type 2 diabetes, and medical management, including lifestyle changes, may not be successful at lowering risk.

Objective: To investigate the relationship between bariatric surgery and incident macrovascular (coronary artery disease and cerebrovascular diseases) events in patients with severe obesity and type 2 diabetes.

Design, setting, and participants: In this retrospective, matched cohort study, patients with severe obesity (body mass index ≥35) aged 19 to 79 years with diabetes who underwent bariatric surgery from 2005 to 2011 in 4 integrated health systems in the United States (n = 5301) were matched to 14 934 control patients on site, age, sex, body mass index, hemoglobin A1c, insulin use, observed diabetes duration, and prior health care utilization, with follow-up through September 2015.

Exposures: Bariatric procedures (76% Roux-en-Y gastric bypass, 17% sleeve gastrectomy, and 7% adjustable gastric banding) were compared with usual care for diabetes.

Main outcomes and measures: Multivariable-adjusted Cox regression analysis investigated time to incident macrovascular disease (defined as first occurrence of coronary artery disease [acute myocardial infarction, unstable angina, percutaneous coronary intervention, or coronary artery bypass grafting] or cerebrovascular events [ischemic stroke, hemorrhagic stroke, carotid stenting, or carotid endarterectomy]). Secondary outcomes included coronary artery disease and cerebrovascular outcomes separately.

Results: Among a combined 20 235 surgical and nonsurgical patients, the mean (SD) age was 50 (10) years; 76% of the surgical and 75% of the nonsurgical patients were female; and the baseline mean (SD) body mass index was 44.7 (6.9) and 43.8 (6.7) in the surgical and nonsurgical groups, respectively. At the end of the study period, there were 106 macrovascular events in surgical patients (including 37 cerebrovascular and 78 coronary artery events over a median of 4.7 years; interquartile range, 3.2-6.2 years) and 596 events in the matched control patients (including 227 cerebrovascular and 398 coronary artery events over a median of 4.6 years; interquartile range, 3.1-6.1 years). Bariatric surgery was associated with a lower composite incidence of macrovascular events at 5 years (2.1% in the surgical group vs 4.3% in the nonsurgical group; hazard ratio, 0.60 [95% CI, 0.42-0.86]), as well as a lower incidence of coronary artery disease (1.6% in the surgical group vs 2.8% in the nonsurgical group; hazard ratio, 0.64 [95% CI, 0.42-0.99]). The incidence of cerebrovascular disease was not significantly different between groups at 5 years (0.7% in the surgical group vs 1.7% in the nonsurgical group; hazard ratio, 0.69 [95% CI, 0.38-1.25]).

Conclusions and relevance: In this observational study of patients with type 2 diabetes and severe obesity who underwent surgery, compared with those who did not undergo surgery, bariatric surgery was associated with a lower risk of macrovascular outcomes. The findings require confirmation in randomized clinical trials. Health care professionals should engage patients with severe obesity and type 2 diabetes in a shared decision making conversation about the potential role of bariatric surgery in the prevention of macrovascular events.

Figure 1.. Flow Diagram for Identification of Eligible Patients Who Underwent Bariatric Surgery and Had Type 2 Diabetes Without a Preoperative History of Macrovascular Disease

^aAdults aged 19 to 79 years old who had a primary bariatric surgical procedure between January 1, 2005, and December 31, 2011. Bariatric procedures identified using a combination of bariatric registries, medical record reviews, International Classification of Diseases, Ninth Revision codes (43.89, 44.31, 44.38, 44.39, 44.68, 44.69, and 44.95), and Current Procedural Terminology procedure codes (43633, 43644, 43645, 43659, 43770, 43775, 43842, 43843, 43844, 43845, 43846, and 43847). ^bPatients with the following were excluded: (1) less than 1 full year of continuous enrollment and drug coverage, (2) a history of gastrointestinal surgery for cancer, (3) gestational diabetes if it was the sole diabetes diagnosis, (4) individuals who experienced any time in pregnancy during the year prior to surgery, (5) any recorded use of prescription anticoagulants, and (6) metformin as the sole indicator of possible type 2 diabetes (no other type 2 diabetes medications, laboratories, or diagnoses). Patients may have more than 1 reason for exclusion. ^cPatients may have more than 1 type of missing data (body mass index [calculated as weight in kilograms divided by height in meters squared], hemoglobin A_1c level). ^deTable 1 in the Supplement shows the characteristics of patients who were excluded due to missing data or inability to match compared with the final analytic sample.

Figure 2.. Cumulative Incidence Rates at All Study Sites

Kaplan-Meier estimates of the cumulative incidence of macrovascular disease and all-cause mortality following bariatric surgery vs matched nonsurgical patients. Separate estimates for coronary artery disease events (B) and cerebrovascular events (C) are shown, as well as a composite estimate for incident macrovascular disease due to either of these event classes (A) and all-cause mortality (D). The median follow-up time among surgical patients was 4.7 years (interquartile range, 3.2-6.2), and among matched nonsurgical patients was 4.6 years (interquartile range, 3.1-6.1).

Figure 3.. Time-Varying Hazard Ratios Comparing Surgical and Matched Nonsurgical Patients

Time-varying hazard ratios comparing the risk of incident macrovascular disease and death following bariatric surgery vs matched nonsurgical patients. Separate estimates for coronary artery disease events (B) and cerebrovascular events (C) are shown, as well as a composite estimate for incident macrovascular disease due to either of these event classes (A) and all-cause mortality (D). The median follow-up time among surgical patients was 4.7 years (interquartile range, 3.2-6.2), and among matched nonsurgical patients was 4.6 years (interquartile range, 3.1-6.1). All analyses used the full cohort of patients who underwent surgery (n = 5301) and matched controls (n = 14 934). Shaded areas represent the 95% CIs.