Bariatric Surgery in Obese Type 1 Diabetes Has Pros, Cons

Marlene Busko

September 25, 2019

BARCELONA — Middle-aged obese patients with type 1 diabetes who had gastric bypass surgery had lower rates of cardiovascular death and stroke but higher rates of diabetic ketoacidosis (DKA) than their peers who did not have surgery, in new research.

This is the largest, longest study of bariatric surgery in type 1 diabetes, with close to 400 case-control dyads and a mean follow-up of almost 5 years, said Gudrun Höskuldsdottir, MD, Sahlgrenska University Hospital, Sweden, who presented the findings in an oral session last week at the European Association for the Study of Diabetes (EASD) 2019 Annual Meeting.

Nevertheless, questions remain. Because patients with type 1 diabetes lack functioning beta cells, they cannot hope for possible remission of diabetes after bariatric surgery (unlike patients with type 2 diabetes), but the operation may help them maintain glycemic control with less insulin.

According to Höskuldsdottir, the current study "meaningfully extend[s] earlier research" in obese patients with type 1 diabetes and suggests "potentially sizeable benefits of gastric bypass surgery...with regard to cardiovascular events and cardiovascular mortality.

“But at the same time, there's a higher risk for serious hyperglycemic events [that] need to be taken seriously," she cautioned, noting four patients died in the surgery group following diabetic coma (compared with one control).

Hence, it is important to evaluate patients with type 1 diabetes for bariatric surgery on a case-by-case basis, she stressed to Medscape Medical News.

And surgeons must work with diabetologists to optimize insulin delivery around the time of the operation, she noted.  

Additionally, patients who can use technology such as continuous glucose monitoring (CGM), for example, may be better able to avoid diabetic ketoacidosis (DKA) after bariatric surgery.

Serious hypoglycemic events were also more common in the surgery group than controls, but not significantly so.

The researchers only had information on hyper- and hypoglycemic events that required hospitalization, and it is especially likely that a number of hypoglycemic events that were treated outside of the hospital were missed, Höskuldsdottir said.

Session co-chair Nils Wierup, PhD, Lund University, Malmo, Sweden, told Medscape Medical News that this cohort is one of the larger samples of obese patients with type 1 diabetes, and the "hyperglycemic and hypoglycemic information that they had is very important" when evaluating whether a patient is a potential candidate for bariatric surgery.

Almost One in Five Patients With Type 1 Diabetes in Sweden Is Obese

Höskuldsdottir noted that whereas the 2018 American Diabetes Association (ADA) Standards of Medical Care in Diabetes guidelines recommend and discuss bariatric (metabolic) surgery for certain patients with type 2 diabetes, they also state that whereas "metabolic surgery has been shown to improve the metabolic profiles of morbidly obese patients with type 1 diabetes, establishing the role of metabolic surgery in such patients will require larger and longer studies."

"I think most of us," she told the audience, "would feel comfortable discussing surgical treatments of obesity with our type 2 diabetes patients."

But "discussing bariatric surgery with your type 1 diabetes patient" is a little more complicated, she said.

However, it's relevant. In Sweden, more than 18% of patients with type 1 diabetes are obese and over 50% are overweight, Höskuldsdottir said.

In their work, the group aimed to compare outcomes after bariatric surgery versus medical care in type 1 diabetes based on data from the National Diabetes Register in Sweden and Scandinavian Obesity Surgery (SoS) registry.

They identified 387 patients in Sweden with type 1 diabetes who underwent Roux-en-Y gastric bypass in 2007-2013 and matched them with 387 controls with type 1 diabetes of the same gender who did not undergo surgery and had a similar age, diabetes duration, and body mass index (BMI).  

On average, patients were 41 years old, with a BMI of 40 kg/m2, diabetes duration of 18.8 years, and suboptimal HbA1c levels.

The primary outcomes were all-cause mortality, cardiovascular mortality, cardiovascular disease, and hypo- or hyperglycemic events (that required hospitalization).

Secondary outcomes, which were not presented at EASD, included changes in kidney function, amputation, psychiatric disorders, and alcohol/drug abuse.

Fewer Strokes, More DKA, and Patient Deaths a Concern

The mean follow-up was 4.7 years (up to 9 years) for cardiovascular disease, DKA, and hypoglycemia, and 5.8 years (up to 10 years) for mortality.

All-cause mortality was lower in the patients who had bariatric surgery, but this outcome was not statistically significant (P = .06).

However, the risk of cardiovascular death during follow-up was significantly lower in the patients who had undergone bariatric surgery (HR, 0.15; P = .013).

Moreover, during the almost 5-year follow-up, those who had bariatric surgery had a much lower risk of heart failure (HR, 0.32; P = .003) and stroke (HR, 0.18; P = .026) than the patients who didn't have surgery, but they had a similar risk of heart attack and atrial fibrillation.

There was a numerical but nonsignificant increase in serious hypoglycemic events in the surgery group.

However, patients who had bariatric surgery had twice the risk of a serious hyperglycemic event (including DKA) that required hospitalization (HR, 1.99; P = .03) starting 2 or 3 days after surgery and persisting.

"It is important to realize that four patients in the gastric bypass group died because of diabetic coma as opposed to one patient in the control group," Höskuldsdottir stressed.

"Although these are not many events I think we should take each case of death in this patient population seriously."

"The early events of hyperglycemia and DKA directly after surgery indicate that there is a need for contact with the diabetes help with insulin dosage," Höskuldsdottir stressed.

"I understand that none of you here would recommend discontinuing or greatly reducing insulin treatment when the surgery is started."

Many Remaining Questions

Study strengths include the fact that the data represent 90% of patients with type 1 diabetes undergoing bariatric surgery in Sweden, Höskuldsdottir noted.

However, there were also some limitations, she said, including a lack of information about use of insulin pumps or CGM, or about changes in weight or glycemic control over time, and it's possible patients who had surgery may have been healthier.

And, she noted, there are further questions, such as, "How do the patients sustain weight loss? Do they regain the weight? How does [Roux-en-Y gastric bypass] compare with medical treatment (very low-calorie treatment) or with gastric sleeve?"

And in reply to a question from the audience, she said the indication for bariatric surgery in type 1 diabetes is based on BMI alone and not on additional indications that apply in type 2 diabetes such as sleep apnea or complications of type 2 diabetes.

"The main focus [in type 1 diabetes] would be BMI, [and] of course there are the same contraindications as for other populations," including alcohol abuse and psychiatric disorders, for example, she noted.

Finally, treatment with GLP-1 receptor agonists and other newer diabetes drugs was not common when the study was conducted, so further research is needed to compare outcomes after bariatric surgery versus medical therapy with these newer agents.

The researchers have reported no relevant financial relationships.

EASD 2019 Annual Meeting. Presented September 19, 2019. Abstract 91.

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