Gastric Bypass Surgery Increases Risk of Fracture

Sofie Ahlin, MD, PhD

Fracture risk increases after gastric bypass surgery, recent study findings showed.

Sofie Ahlin, MD, PhD, and a team of investigators investigated the association between different bariatric surgery procedures and fracture risk. The findings emphasized the need for long-term follow-up of bone health for patients undergoing such treatment.

Ahlin, of the University of Gothenburg in Sweden, collected information on fracture events from the Swedish National Patient Register. The team ultimately analyzed 2007 patients treated with 1 of 3 bariatric surgeries—gastric bypass, gastric banding, or vertical banded gastroplasty—and 2040 control patients with obesity matched on a group level. Variables included age, sex, height and weight, and waist and hip circumferences.

The investigators searched the same database for ICD-9 and 10 codes for fractures that required hospitalization or specialist outpatient treatment. Vertebrae, distal forearm, proximal humerus, and proximal femur fractures were considered major osteoporotic.

Risk factors for osteoporosis and fracture included age; sex; smoking; excessive alcohol intake; premature menopause; and a previous history of fractures. Baseline questionnaires were used to obtain such data.

Patients in the study received a discharge questionnaire which had information about recommended mineral and vitamin supplementation after surgery. For some patients, it was suggested they had multivitamin supplementation at the time of surgery, but no other additional calcium or vitamin D supplementation was recommended at baseline.

Median follow-up for fractures was 17.6 years (IQR, 14.2-20.8) in control patients and 17.9 (IQR, 7.2-21.1), 17.8 (IQR, 13.4-20.6), and 15.1 (IQR, 13.9-19.1) years in those who underwent gastric banding, vertical banded gastroplasty, and gastric bypass.

The mean weight loss at 1-year follow-up in the bariatric surgery group was between 20-32% for the different surgical procedures. Due to partial weight regain, mean weight loss at the 10-year follow-up was between 14-24%. At all time-points, weight loss was greater after gastric bypass than banding or vertical banded gastroplasty.

The incidence rate for first-time fracture during follow-up was 22.9 per 1000 person-years (95% CI, 18.5-28.3) in the gastric bypass group. Incidence rates were 10.4 (95% CI, 9.1-11.9), 10.7 (95% CI, 8.2-14), and 9.3 (95% CI, 8.3-10.4) for vertical banded gastroplasty, gastric banding, and control cohorts. Overall, gastric bypass surgery was associated with a higher risk of first-time fracture than typical care (HR, 2.64; 95% CI, 2.07-3.36; P <.001). The association was statistically significant even after multivariable adjustment for preselected risk factors and inclusion year (adjHR, 2.58; 95% CI, 2.02-3.31; P <.001).

Vertical banded gastroplasty was associated with a slightly higher risk of first-time fracture compared with usual care (adjHR, 1.2; 95% CI, 1-1.43; P=.047). Gastric bypass led to higher risk of first-time fracture compared with vertical banded gastroplasty and gastric banding (adjHR, 2.15; 95% CI, 1.66-2.79; and adjHR, 1.99; 95% CI, 1.41-2.82; P <.001).

What’s more, gastric bypass was linked to higher risk for first-time major osteoporosis fracture compared to gastric banding (adjHR, 1.94; 95% CI, 1.24-3.05; P=.004) and vertical banded gastroplasty (adjHR, 3.14; 95% CI, 2.19-4.51; P <.001).

The study results should be considered a serious long-term side effect, the study authors noted, because fracture could lead to disability, lost productivity, increased medical costs, and suffering.

The study, “Fracture risk after three bariatric surgery procedures in Swedish obese subjects: up to 26 years follow-up of a controlled intervention study,” was published online in the Journal of Internal Medicine.