Bariatric Surgery Reduces Diabetes-Associated Vascular Disease in Obese Patients

Studies have shown that obesity increases the risk for diabetes and that diabetes is associated with microvascular and macrovascular complications.

Lena Carlsson, MD, PhD, professor in the Department of Molecular and Clinical Medicine, The Sahlgrenska Academy, University of Gothenburg, Sweden, and her colleagues have previously shown that bariatric surgery strongly reduces the risk for diabetes in obese patients and prevents microvascular and macrovascular complications in obese patients with diabetes.

At ENDO 2015, Carlsson presented data from a study to determine the effects of bariatric surgery on the long-term risk of microvascular and macrovascular events in obese patients without diabetes at baseline. Patients were enrolled in the ongoing Swedish Obese Subjects (SOS) trial. This is a prospective, matched intervention study conducted at 25 surgical departments and 480 primary healthcare centers in Sweden. The primary outcome measure is mortality and secondary outcomes are the incidences of diabetes mellitus, myocardial infarction, and stroke. Carlsson emphasized that it is not a randomized trial. Back in 1987, when the SOS study began, it was not permitted to randomize patients who were candidates for gastric bypass.

In this study, participants were 37 to 60 years of age, with a BMI of 34 or greater in men and 38 or greater in women. Carlsson presented data from 3,429 patients in the SOS study that did not have diabetes at baseline. Of these, 1,658 patients underwent bariatric surgery (19% adjustable gastric banding, 69% vertical banded gastroplasty, 12% gastric bypass) and the remaining subjects were 1,771 obese matched controls receiving standard non-surgical obesity care.

Microvascular (eyes, kidneys and peripheral nerves) and macrovascular (legs, heart and brain) events requiring hospital or specialist outpatient treatment or that were associated with death during follow-up were traced by searching the Swedish Cause of Death Register and the Swedish National Patient Register. These registries are 99% complete as regards medical evidence associated with deaths. The median follow up time was 18 years.

Carlsson reported that bariatric surgery reduced the incidence of microvascular plus macrovascular events, whichever occurred first, in patients without diabetes at baseline (566 and 411 events in the control and surgery groups, respectively; HR=0.73; 95%CI: 0.64-0.82; p<0.001).

When the incidence of microvascular and macrovascular events were analyzed separately, both were reduced in the surgery group compared to controls (HR=0.48; 95%CI: 0.38-0.60; p<0.001 and HR=0.80; 95%CI: 0.70-0.92; p<0.002 for microvascular and macrovascular events, respectively). The reduction of the incidence of microvascular plus macrovascular events was more pronounced in patients with prediabetes at baseline compared to those with normal glucose status (HR=0.52; 95%CI: 0.40-0.68; p<0.001 and HR=0.79; 95%CI: 0.68-0.91; p<0.001, respectively; interaction p-value=0.005).

In summary, bariatric surgery reduced the risk of developing microvascular or macrovascular events or complications overall by 30%. This breaks down into a 20% decrease in macrovascular events and a 50% decrease in microvascular events. The effect was more pronounced in patients with abnormal fasting blood glucose compared with normoglycemic patients.

Carlsson emphasized that, since gastric procedures are permanent treatments, patients should be followed and monitored for long-term outcomes. It was critical to monitor for nutritional deficiencies.

After her presentation, Carlsson was asked who should care for the patient after surgery. She said not the surgical team. The patient should be managed in the primary care setting. However, in Sweden this was not yet customary. Another questioner asked about the effects of the three different surgical procedures. Carlsson replied that they hadn’t observed any differences; other than in percent weight loss, of course. However, she said that their study was not powered to discriminate between procedures.