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Bariatric surgery seems "markedly more efficient than usual care" at preventing type 2 diabetes in obese patients, Swedish researchers said today in the New England Journal of Medicine.
In their case-control study, surgery cut the long-term risk of type 2 diabetes by 78%. Among the 1 658 patients who had surgery, mostly vertical banded gastroplasty, the risk of diabetes was 0.68% per year. The risk was four times higher - 2.84% per year - in the 1 771 people in the standard-care group.
"Most of the previous studies on bariatric surgery have focused on the remission of diabetes. This study is more about preventing diabetes," Dr Ted Adams of the University of Utah, who was not connected with the research, said.
"We saw a marked delay (in the development of diabetes) over 15 years," said coauthor Dr Lars Sjostrom of the University of Gothenburg in Sweden. "Some of those surgical patients will probably develop diabetes later. But over a lifetime, there will be a large difference."
Overweight people had higher risk
The improvement was seen even though the people who underwent surgery initially had a higher risk of developing diabetes than those in the control group. "If anything, the surgery group was a bit heavier and had more risk factors than the control group at the start of the study, and still the outcome at 10 years and 15 years was much more favourable in the surgery group," Dr Sjostrom said. "It's favourable in spite of these differences."
The team also found that baseline body mass index wasn't linked with type 2 diabetes risk. Baseline blood glucose levels were better indicators. Dr Sjostrom said a similar effect was seen in studies that looked at the impact of the surgery on rates of heart attack, stroke, cancer prevention and overall mortality.
As a result, "it may be time to give less attention to the degree of obesity when patients are selected for bariatric surgery," he said. In a Journal editorial, Dr Danny Jacobs of Duke University School of Medicine in Durham, North Carolina said, "It remains impractical and unjustified to contemplate the performance of bariatric surgery in the millions of eligible obese adults."
But the results may help doctors understand why the various types of surgery work and pick out the best candidates for the operation, he said. Dr Sjostrom said more studies are needed and a cost analysis of the pros and cons of surgery, now underway, could be published in a year or so.
Findings of doctors
"It may turn out that this is very cost effective," he said. "You might even save money if you operate on patients with impaired fasting glucose because if you operate on 13 such patients, you prevent diabetes in 10 of them."
Dr Jaime Ponce, president of the American Society for Metabolic and Bariatric Surgery, said the study is more evidence that being overweight is important for the development of diabetes.
Three patients (0.2%) died within 90 days of their surgery, 4.8% had lung complications, 3.2% suffered vomiting, 3.5% had infections, and 2.1% developed a haemorrhage or thromboembolism. The 90-day reoperation rate was 2.8%.
The authors note that the link between obesity and diabetes is well documented, and making lifestyle changes or taking weight-reducing drugs can cut the risk of diabetes by 40% to 45%. The new study, part of the larger Swedish Obese Subject (SOS) study, was designed to see if the surgical weight loss would have the same effect. None of the patients included in the test had diabetes when the project began in 1987. Enrolment ended in February 2001.
Those who had the surgery
In the surgery group, the average weight loss at the 10- and 15-year mark was 20 kg. The control group members typically stayed around 3 kg from their starting weight. The matched control patients received standard preventive care consisting of recommendations for healthier eating and more physical activity. The researchers calculated, after adjusting for various factors, that the surgery cut the risk of diabetes by 83% (p<0.001).
"Among patients with impaired fasting glucose, bariatric surgery reduced the risk by 87%, and type 2 diabetes did not develop in approximately 10 of 13 obese patients who underwent bariatric surgery. This risk reduction is at least twice as large as that observed with lifestyle interventions in moderately obese, pre-diabetic persons," said the research team, led by Dr Lena Carlsson, also of the University of Gothenburg.
According to Utah's Dr Adams, "This is simply additional information that can help a patient and clinician regarding whether to have the surgery, as they weigh a number of factors. Preventing diabetes is really a meaningful contribution to the long-term quality of life."
In 2009, SOS researchers concluded that weight-loss surgery reduced the risk of cancer in obese women. In 2007 they reported that it reduced long-term mortality.
(Reuters Health, Gene Emery, August 2012)
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