Contemporary Bariatric Surgery Cuts Type 2 Diabetes by 80%

Miriam E. Tucker

November 04, 2014

Bariatric surgery reduced the risk of developing type 2 diabetes by 80% among patients in a new UK study with up to 7 years of follow-up.

Results from the retrospective review of 2167 bariatric-surgery patients and the same number of matched controls from the UK primary-care database were published online November 3 in Lancet Diabetes & Endocrinology by Helen Booth (King's College London, United Kingdom) and colleagues.

The research is the first to document type 2 diabetes prevention from bariatric surgery in a real-world setting using current bariatric-surgery methods, say the authors. A previous prospective study, the Swedish Obese Subjects (SOS) study, has produced similar findings, but a majority of patients had undergone the now-outmoded vertical banded gastroplasty, Ms Booth and colleagues note.

"This is the first contemporary, pragmatic study to show that weight-loss surgery prevents the development of diabetes," study coauthor Dr Omar Khan (Whittington Hospital, London, United Kingdom) told Medscape Medical News.

Dr Khan said that currently less than 1% of people in the UK who could benefit from bariatric surgery actually receive it and that obese people typically aren't referred for bariatric surgery until they've already developed diabetes and its complications.

"The message from our paper is you're better off actually, once you've got someone who's obese, intervening earlier, before they get diabetes, because it's better for them and it's better in terms of cost-effectiveness."

But in an accompanying editorial, Dr Jacques M Himpens (St Pierre University Hospital, Brussels, Belgium) sounds a note of caution.

"Although the results of Ms Booth and colleagues bring us a step closer to confirming the effect of bariatric surgery on the incidence of de novo type 2 diabetes, many questions still remain unanswered, and more evidence is needed to convince endocrinologists about the nature of this effect."

Bariatric Surgery Resulted in 80% Prevention Compared With Usual Care

The new data on the outcomes from bariatric surgery come from the Clinical Practice Research Datalink (CPRD), which includes electronic health records for five million patients in 680 UK primary-care practices.

Of 2167 patients who underwent bariatric surgery between 2002 and April 2014, 49% received laparoscopic gastric banding, 37% had gastric-bypass procedures, and 15% underwent sleeve gastrectomy. (Two people had codes for more than one procedure.)

Controls were matched for age, sex, and body mass index (BMI), which was 40 kg/m2 or greater in about 60% of the patients.

By the end of follow-up — 7 years maximum, 2.8 years median — 4.3% of the bariatric-surgery patients had been diagnosed with type 2 diabetes, compared with 16.2% of the controls. Incidence rates of type 2 diabetes were 5.7 vs 28.2 per 1000 person-years, respectively.

After adjustment for baseline characteristics including age, BMI, sex, and HbA1c, the hazard ratio for the development of diabetes with bariatric surgery compared with usual medical care was 0.20 (P < .0001).

The effect of bariatric surgery on new-onset diabetes was similar among men and women and across age groups.

After adjustment, diabetes rates were even lower for gastric bypass and sleeve gastrectomy, although there was a decreased risk with laparoscopic banding as well.

The numbers are too small to draw firm conclusions as to which type of bariatric surgery best prevents diabetes and other outcomes, but the researchers are now using CPRD data to further investigate this, Dr Khan told Medscape Medical News.

Results were similar in several sensitivity analyses, including a comparison against the entire database of over 100,000 obese people without diabetes (hazard ratio [HR], 0.16), exclusion of those diagnosed with diabetes within a year of the surgery date (HR, 0.20), exclusion of women with gestational diabetes (HR, 0.19), and allowing for the competing risk of death (HR, 0.20).

A Truly Pragmatic Study

"These findings are important because they provide further evidence that bariatric surgery can reduce the risk of type 2 diabetes in obese people," Dr Himpens notes in his editorial.

But he also finds fault with the study, for what he deems is inadequate matching of the two study groups, as well as the short follow-up time.

For example, he points out that, unlike the prospective SOS study, the controls here received no particular weight-loss intervention of any kind, and their records had far more missing data: 68% of the controls were lacking information on cholesterol compared with just 26% of the bariatric-surgery group, for instance.

"The frequency of missing data in the control group seems to confirm widely held beliefs that many family doctors do not view obesity as a disease and think obese people do not need treatment and monitoring," he says.

"Conversely, the bariatric-surgery patients, who were treated by the most active means against obesity (ie, surgery), are clearly a select category of individuals who were monitored closely."

Dr. Khan told Medscape Medical News that the study reflects reality.

"This is probably reflective of real-life medicine. Most obese people get no medical care at all in the UK. And we know [even] the best medical care for obesity doesn't work, anyway."

He added that although the surgical patients probably were well-monitored before and after their surgery, they didn't necessarily receive the best medical care for their obesity. "That's why I say it's a truly pragmatic study."

What About Weight Regain and Diabetes With Longer Follow-up?

With regard to the length of follow-up (median 2.8 years), Dr Himpens observes "most patients who undergo bariatric procedures regain weight over time, an important consideration in the context of diabetes."

He notes that one study with more than 8 years of follow-up showed that more than 40% of patients who underwent gastric bypass relapsed after initial remission from diabetes.

"Thus, other factors seem to affect the natural history of type 2 diabetes after bariatric surgery. Hence, whether altered anatomy after bariatric surgery provides continued protection against de novo type 2 diabetes in the case of weight regain remains an open question."

In response, Dr Khan told Medscape Medical News, "It's possible that over time some of the surgery patients who don't have diabetes will develop diabetes. But in the worst-case scenario, we're postponing the development of diabetes, which is not a bad thing. If you can reduce the number of years you have diabetes, we know that will reduce end-organ damage."

And, he added, "In the group that didn't have surgery, I suspect a lot of them will be gaining weight even more than those who had weight-loss surgery. I suspect the disparity will actually grow over time."

Dr Khan said that while he sees prevention of obesity as the long-term goal — with political measures such as sugar and fat taxes and changes in food packaging — bariatric surgery is the best short-term solution.

"In the short to medium term, what do you do with someone who's already got a BMI of over 40? We know any form of intervention is too late….This paper, in combination with lots of others, demonstrates the benefits of bariatric surgery in both treating diseases like diabetes and preventing them from occurring in the first place."

The study was funded by the UK National Institutes for Health Research Health Services and Delivery Research program. Ms Booth and Dr Khan report that they have no relevant financial relationships; disclosures for the coauthors are listed in the article. Dr Himpens has received personal fees as a consultant for Ethicon Endosurgery.

Lancet Diabetes Endocrinol. Published online November 3, 2014. Abstract

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