MELBOURNE – The benefits of bariatric surgery in people with type 2 diabetes are significantly reduced with longer disease duration at the time of surgery and with time since surgery, a long-running, prospective, controlled study has found.
The Swedish Obese Subjects study showed that 72% of surgery patients achieved remission at 2 years after treatment, compared with 16% of control patients.
Furthermore, 15 years after surgery, 31% of the surgery patients remained in remission, compared to 7% of control patients, according to data presented at the International Diabetes Federation world congress.
When stratified by disease duration at baseline, newly diagnosed patients maintained significantly higher remission rates at 2, 10 and 15 years’ follow-up (roughly 94%, 60%, and 47%, respectively) than did those who had had diabetes for more than 3 years at baseline (about 39%, 12%, and 9%).
Dr. Markku Peltonen
These data came from the SOS (Swedish Obese Subjects) study, a nonrandomized, prospective, observational study involving 2,010 obese subjects who underwent bariatric surgery in 1987-2001, when they were 37-60 years old. A total of 68% of the bariatric surgery recipients had vertical band gastroplasty, 19% underwent gastric banding, and 13% had a Roux en-Y gastric bypass. They were extensively matched by 18 variables to 2,037 obese controls. The SOS study is being conducted at 25 surgical departments and 480 primary care clinics across Sweden. Follow-up is ongoing.
There were 343 individuals with type 2 diabetes in the surgical group and 260 in the control group, enabling a secondary analysis of the impact of bariatric surgery in type 2 diabetes.
Presenter Markku Peltonen said that although bariatric surgery achieves impressive results in the short-term, there is considerable relapse in the longer term.
"It’s typical of bariatric surgery that you achieve the greatest weight loss initially, after 2 years, then there is a slow regain again and this was observed in this study," said Dr. Peltonen, director of the department of chronic disease prevention at the National Institute for Health and Welfare, Helsinki.
"Even in the long term, they are doing much better than the controls who were treated with traditional weight management means," he said in an interview.
This also extended to the microvascular and macrovascular complications of diabetes, with the study showing a significant 47% lower incidence of complications in the surgery group, compared with the control group.
However, these benefits were also attenuated by disease duration. Patients who had had diabetes for more than 3 years and were treated with surgery showed no significant differences in diabetes complication rates, compared with the patients given medical care only.
Dr. Peltonen said he was surprised by the degree of impact that disease duration had on the outcomes of surgery.
"Somehow the expectation would be that we would see an effect even in those people with long diabetes duration, because they have a serious, advanced disease but it looks like, based on our results, that maybe it’s so that the disease has advanced for so long that bariatric surgery cannot reverse that development."
Session chair John Dixon said the SOS study represented the pinnacle of long-term data for bariatric surgery, and offered impressive insights.
"The fact that 31% of these patients are still in remission from diabetes some 15 years down the track is extraordinary, because we know the deterioration of beta cells is significant and this group has held it off for a long time," said Dr. Dixon, head of clinical obesity research at the Baker IDI Heart and Diabetes Institute in Melbourne.
Dr. Dixon said the finding that patients treated early fared better and had a reduction in long-term complications was also a very important clinical finding, suggesting that bariatric surgery should be considered earlier in obese patients not getting good control with conventional therapy.
SOS was supported by the Swedish Research Council, the Swedish Foundation for Strategic Research, and the Swedish government. Some study investigators authors had received paid lectureships, held stock in, or were on the advisory boards for pharmaceutical companies.