Gastric Bypass Ups Fracture Risk, Need for Long-term Management

Liam Davenport

May 22, 2019

Patients, including those aged 65 years or older, who undergo Roux-en-Y gastric bypass (RYGB) for severe obesity should be followed long term for fractures, because they face a substantially increased risk compared with those who undergo adjustable gastric banding (AGB), say US investigators.

Elaine W. Yu, MD, Endocrine Unit, Massachusetts General Hospital, Boston, and colleagues examined the Medicare claims data of more than 42,000 individuals who underwent bariatric surgeries during an 8-year period.

They found that after an average follow-up of 3.5 years, RYGB patients had a 73% increased risk for nonvertebral fractures in comparison with AGB patients.

The risk for hip fractures was almost threefold higher among RYGB patients vs those in the AGB group. The risk for wrist fracture was 70% higher, and that for pelvis fracture was almost 50% greater.

The study, published online in JAMA Surgery on May 15, showed that the increased risk could not be explained by age, sex, diabetes status, or race. The fracture risk patterns seen among individuals aged 65 years or older were similar to those of younger patients.

The team writes that, despite the "myriad health benefits" associated with bariatric surgery, "increased fracture risk is an important factor to discuss with patients seeking RYGB."

They suggest that, on the basis of their findings, "aggressive management of bone health (eg, bone density scans, calcium and vitamin D supplementation and physical activity) is warranted."

Sleeve Gastrectomy Would Have Been Better Comparator

In an accompanying editorial, Margaret E. Smith, MD, and Amir A. Ghaferi, MD, from the Department of Surgery, University of Michigan, Ann Arbor, commend the authors for conducting the study, although they note that it has several limitations.

They highlight the fact that although the fracture rate may be significantly different between RYGB and AGB patients, "the clinical effect of minimal absolute differences in fractures is likely insignificant." For example, despite a hazard ratio of 2.81, only 103 patients who underwent RYGB (0.4%) experienced a hip fracture, compared with 25 (0.2%) of the gastric band cohort.

Moreover, gastric banding may not have been the ideal comparator to RYGB, because the former is a "rapidly declining" procedure. They comment that sleeve gastrectomy may have offered a "more salient" comparison.

Smith and Ghaferi nevertheless say that the results of the study "highlight a necessary shift in perspective from short-term outcomes of bariatric surgery to the long-term management and mitigation of potential unintended effects.

"As bariatric surgery is often referred to as a 'life-long' treatment for obesity, physicians should focus on long-term outcomes and managing the longitudinal effects of this life-saving treatment."

RYGB Ups Fracture Risk by 70% Compared With Gastric Band

The number of bariatric surgery procedures has increased in recent years. Numerous trials have shown that it leads to greater weight loss and is more cost-effective than lifestyle and medical treatments for severe obesity, say Yu and colleagues.

However, studies have indicated that bariatric surgery is associated with an increased risk for fractures at sites typically seen in osteoporosis and that bone loss continues up to 5 years post surgery.

The researchers note, however, that few older adults have been included in studies that assessed fracture risk, despite bariatric surgery increasingly being offered to individuals aged 60 years or older.

They therefore gathered Medicare claims data for the period 2006 to 2014 on people with severe obesity who underwent bariatric surgery with either RYGB or AGB, a procedure that is not associated with an increased fracture risk.

From an initial cohort of 3,908,991 individuals with severe obesity, the team selected 29,624 who had undergone RYGB and 12,721 who had undergone AGB.

RYGB patients were, on average, younger than those who received AGB, at 51 years vs 55 years. For both RYGB and AGB, the majority of patients were women (78.8% and 77.9%, respectively).

Rates of hypertension, diabetes, chronic obstructive pulmonary disease, and medication use were similar for the two groups, although RYGB patients were more likely to have fatty liver disease. The combined comorbidity scores were similar between the two arms.

During a mean follow-up of 3.3 years for RYGB patients and 3.9 years for AGB patients, 4.7% and 0.5%, respectively, were censored as a result of patients undergoing a second bariatric operation.

A total of 658 fractures occurred during follow-up.

The overall incidence rate for fracture was 6.6 per 1000 person-years with RYGB, vs 4.6 per 1000 person-years for AGB.

Multivariate analysis that was adjusted for demographic characteristics, medical history, and medication use indicated that RYGB was associated with a significantly increased risk for nonvertebral fractures, at a hazard ratio (HR) of 1.73.

Specifically, there was an increased risk for fracture with RYGB in comparison with AGB at the hip (HR, 2.81), wrist (HR, 1.70), and pelvis (HR, 1.48).

With respect only to individuals aged 65 years or older, the team found that the incidence rate of nonvertebral fractures was 9.9 per 1000 person-years with RYGB, vs 5.3 per 1000 person-years for AGB.

The adjusted risk for nonvertebral fractures with RYGB vs AGB was similar to that seen in the overall population, at an HR for any nonvertebral fracture of 1.75.

For hip fracture, the HR with RYGB vs AGB among individuals aged 65 years or older was 2.51; the HR for wrist fracture was 1.65.

Sex, age, diabetes status, and race did not significantly modify the association between RYGB and fracture risk. The team used propensity score matching and found very similar outcomes.

What's the Explanation?

In explaining the increased fracture risk following RYGB, the researchers say that the mechanism is "likely multifactorial" and may include skeletal unloading due to the weight loss and calcium malabsorption post surgery.

They add: "Many RYGB-associated alterations in gut hormones, metabolism, and the microbiome have the potential to directly alter bone physiology, although to date none has been causally proven to instigate bone loss after RYGB."

As for the prevention of RGYB-associated fractures, the team says that the appropriate strategy "is not clear."

Studies have shown that vitamin D, calcium supplementation, and exercise can slow bariatric surgery-related bone loss. The authors note that guidelines for health management recommend supplementation and that exercise and protein supplements may be beneficial.

"In theory, careful use of antiresorptive osteoporosis agents could inhibit high bone turnover associated with RYGB, but no trials have been conducted to test the safety and efficacy of this therapeutic strategy," they conclude.

The study was supported by National Institutes of Health grants and the Clinical Scientist Development Award from the Doris Duke Charitable Foundation. Yu has received research grants from Seres Therapeutics for unrelated studies. Coauthor Seoyoung C. Kim, MD, ScD, has received research grants from Pfizer, Bristol-Myers Squibb, and Roche for unrelated studies. Other coauthors have disclosed no relevant financial relationships. Smith has received a National Institute of Health Obesity Surgery Scientist Training Grant. Ghaferi has received grant support from the Agency for Healthcare Research and Quality, a Patient-Centered Outcomes Research Institute Award, and salary support from Blue Cross Blue Shield of Michigan as the director of the Michigan Bariatric Surgery Collaborative.

JAMA Surg. Published online May 15, 2019. Abstract, Editorial

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