Diabetes Risk Drops along with the Weight after Bariatric Surgery

By: MITCHEL L. ZOLER, Clinical Endocrinology News Digital Network

BARCELONA – Patients with type 2 diabetes who undergo bariatric surgery benefit from an increasingly reduced incidence of macro- and microvascular complications over the ensuing 20 years compared with matched controls, based on 20-year follow-up of more than 600 patients treated in Sweden.

The rate of complications that were prevented accelerated during 20 years of follow-up even though the prevalence of patients in remission from type 2 diabetes following bariatric surgery fell over time, with a nadir in remission reached at 20 years, Dr. Lars Sjötröm reported at the annual meeting of the European Association for the Study of Diabetes.

Dr. Sjötröm and his associates previously reported results from the Swedish Obese Subjects (SOS) study showing that among the subgroup of patients who entered the study with diabetes, 72% were in remission from diabetes 2 years after bariatric surgery, and 36% were still in remission 10 years after surgery (N. Engl. J. Med. 2004;351:2683-93). Longer follow-up data he reported at the meeting show that after 15 years the remission rate dropped further to 30%, and after 20 years just 18% of the starting population remained in remission of their diabetes. After 20 years, roughly three-quarters of the patients who initially went into remission of their diabetes had relapsed back into active diabetes.

Despite this, the incidence of macro- and microvascular complications continued to fall compared with the control patients, reported Dr. Sjötröm, professor of medicine at the University of Gothenburg, Sweden, and lead investigator of SOS. The rate of complications of the eyes, kidneys, peripheral nerves, or peripheral circulation that required hospitalization was about 8% in the surgery patients and 12% in the controls after 10 years, and after 20 years the rates were about 20% in the surgery patients and 45% in the controls, a 54% relative risk reduction in favor of surgery that appeared greater than after 10 years. His group previously reported a similar finding for the incidence of myocardial infarctions (Diabetes Care 2012;35:2613-7).

"I think you should operate on patients with diabetes; we saw a drop in their complications," he said. "Even when patients relapse, their cardiovascular risk factors are still improved. This may be why we see an effect on complications despite the patients relapsing. Even with all the relapses, the effect of surgery on diabetic complications remains strong after 20 years." Gastric bypass surgery appeared to offer a feasible operation that also resulted in good diabetes control, he added.

The SOS enrolled 607 patients with diabetes out of the 4,047 total patients in the study. The diabetes subgroup comprised 345 who underwent some form of bariatric surgery, and 262 matched controls who did not receive surgery. Their average age was 50 years, their average body mass index was 40 kg/m², and they had diabetes for an average of 3 years.

In addition to producing diabetes remission and preventing complications, surgery also blunted the incidence of new-onset diabetes. A prior report from SOS showed prevention of new-onset diabetes in the surgery group through the first 15 years of follow-up, (N. Engl. J. Med. 2012;367:695-704), and after 20 years this effect "remained quite strong," with a 77% relative risk reduction in incident diabetes during 20 years of follow-up compared with the controls, Dr. Sjötröm reported.

He also called for scaling back body mass index criteria for performing bariatric surgery because the benefits following surgery appeared similar in patients with relatively low BMIs. He cited a recent analysis his group ran on the 233 patients from SOS who did not meet current criteria for bariatric surgery because their BMI was too low. The average BMI in this subgroup was 36 kg/m², and 104 of these patients underwent bariatric surgery (Diabetes Care 2013;36:1335-40). This exploratory analysis of SOS results showed that the benefits from bariatric surgery were similar in patients with lower BMIs and in patients with higher BMIs who meet the standard surgical criteria.

"Current BMI-based eligibility criteria [for bariatric surgery] are not valid," Dr. Sjötröm declared. "Baseline BMI does not predict any treatment effect examined so far. We should give more importance to metabolic variables to select the patients who would benefit the most from bariatric surgery."

SOS has been supported by grants from Astra Zeneca, Cederroth, Hoffman-La Roche, Johnson & Johnson, and Sanofi-Aventis. Dr. Sjötröm has been a speaker for Astra Zeneca and Johnson & Johnson, and he serves on the board of Lenimen.

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