Bariatric Surgery for Obesity Reduces Some Risks, Raises Others

Miriam E Tucker

January 16, 2018

Bariatric surgery reduces the long-term rates of hypertension, type 2 diabetes, and other obesity-related medical conditions, but those advantages must be weighed against the risks of surgery-related complications and diminished effects beyond 5 years.

These are among the conclusions from two studies published January 16 in the Journal of the American Medical Association as part of an obesity-related theme issue.

One, a large cohort study by Gunn Signe Jakobsen, MD, of the Morbid Obesity Centre, Vestfold Hospital Trust, Tønsberg, Norway, showed that bariatric surgery reduced the risk for hypertension and other obesity-related comorbidities but also raised the risk for surgery-related complications at a median of 6.5 years.

"The risk for complications should be considered in the decision-making process," Dr Jakobsen and colleagues write.

And in a smaller observational 5-year follow-up study, Sayeed Ikramuddin, MD, of the Department of Surgery, University of Minnesota, Minneapolis, and colleagues found that adults with type 2 diabetes randomized to gastric bypass in addition to lifestyle had significantly better glycemia, cholesterol, and blood pressure levels compared with those randomized to medical management with lifestyle.

However, because the effect size was diminished over 5 years, "further follow-up is needed to understand the durability of the improvement," Dr Ikramuddin and colleagues say.

In other related articles in the same issue of JAMA, as reported by Medscape Medical News, researchers report that the popular new bariatric procedure of sleeve gastrectomy seems to be nearly as good an option as gastric bypass. The decision as to which specific surgery is best for any individual patient needs to be shared by the patient and surgeon, taking into account risks and benefits for each individual, they say. Another report showed that severely obese patients who received 'usual care' were twice as likely to die during a median follow-up of 4 years compared with those who underwent bariatric surgery. 

Less Hypertension and Other Comorbidities, but More Complications

In the larger Norwegian study, Dr Jakobsen and colleagues analyzed changes in obesity-related comorbidities following bariatric surgery or specialized medical treatment in 1888 severely obese patients (body mass index [BMI] ≥ 40 or ≥ 35 kg/m2 with at least one comorbidity at baseline).

Patients had chosen their respective treatments. Those who opted for medical treatment could choose between individual- or group-based programs in the outpatient clinic or at a rehabilitation center. Those opting for surgery were significantly younger and had higher BMIs; 92% underwent gastric bypass and 7% underwent sleeve gastrectomy.

For the coprimary outcomes, hypertension remission (based on dispensed drugs) was twice as likely with surgery, and risk for new-onset hypertension was significantly cut by 60% compared with medical treatment.

Endpoint Absolute Risk, % Surgical Group
(n = 932)
Absolute Risk, % Medical Group
(n = 956)
Risk Difference, % Relative Risk
Hypertension remission 31.9 12.4 19.5 2.1
Hypertension, new onset 3.5 12.2 8.7 0.4
Diabetes remission 57.5 14.8 42.7 3.9
New-onset diabetes 0.3 7.5 7.2 0.07
Dyslipidemia remission 43.0 13.2 29.8 2.6
New-onset dyslipidemia 1.1 6.4 5.3 0.3
Depression, new onset 8.9 6.5 2.4 1.5
Opioid use, new onset 19.4 15.8 3.6 1.3
Any gastrointestinal surgery 31.3 15.5 15.8 2.0


Among the prespecified secondary outcomes, surgically treated patients had significantly higher rates of both diabetes and dyslipidemia remission and lower overall risks for new-onset diabetes and dyslipidemia.

However, surgery patients also had greater risks for new-onset depression and anxiety/sleep disorders (RR 1.3) and opioid treatment.

And surgical patients had higher risks for several complications related to the procedure, including having an additional gastrointestinal surgical procedure and abdominal pain (26.1% vs 13.5%; RR 1.9). 

On the more positive side, at long-term follow-up relatively few patients had vitamin and mineral deficiencies, protein malnutrition, nausea/vomiting, or hypoglycemia (< 3% for all cases).

Diabetes-Related Benefits Persist at 5 Years, but Level Off

The smaller study by Dr Ikramuddin and colleagues was an observational follow-up of a randomized clinical trial conducted at four sites in the United States and Taiwan, involving 120 patients with a hemoglobin A1c (HbA1c) of 8.0% or higher and BMI 30.0 to 39.0 kg/m2.

All patients received lifestyle intervention, then 60 had intensive medical management while the other 60 underwent gastric bypass.

Patients were followed for 5 years, at which point data were obtained from 43 in the medical management group and 55 in the gastric bypass group.

The primary composite triple endpoint was HbA1c less than 7.0%, low-density lipoprotein cholesterol less than 100 mg/dL, and systolic blood pressure less than 130 mmHg at 5 years.

In the first year after randomization, the triple endpoint was achieved by 50% in the gastric bypass group vs 16% with medical management (P = .003).

Achievement of the endpoint dropped in both groups from year 1 to year 3, and remained stable for year 3 to year 5. By 5 years, the proportions of patients achieving the triple endpoint were 23% with gastric bypass and 4% with medical management (P = .01).

For HbA1c specifically, the net treatment difference at 5 years was 1.6% (P < .001) in the gastric bypass group. Both groups experienced a substantial decrease in HbA1c in the first year — although greater with the surgery — followed by nearly equal gradual rebounds in both groups.

Full diabetes remission, defined as HbA1c less than 6.0% at all visits for 1 year without taking any glucose-lowering medications, was achieved in approximately nine participants (16%) in the gastric bypass group at 2 years, but declined to 4 (7%) at year 5.

A total of 66 and 38 adverse events occurred in the surgery and medical treatment groups, respectively, by 5 years. Fourteen episodes of surgical complications occurred in the surgery group, while nearly equal numbers — 15 bypass and 16 medical — experienced gastrointestinal events.

Bone fractures, previously reported at 3 years, were not seen in years 3 to 5.

Vitamin B12 deficiency was present in two participants (4%) in the gastric bypass group and one (3%) in the medical management group. Three participants (6%) in the gastric bypass group had anemia vs none in the medical management group.

"It is important to consider the adverse events associated with surgical treatment," Dr Ikramuddin and colleagues conclude. 

Dr Jakobsen received funding from the Vestfold Hospital Trust. Dr Ikramuddin serves as an advisory board member for Novo Nordisk, USGI Medical , and Medica, consults for Metamodix, and receives grant support from Medtronic, ReShape Medical, and institutional support from EnteroMedics.

JAMA 2018;319:291-301. Abstract

JAMA 2018;319:266-278. Abstract

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