FRI079 Long-term Bone Consequences Of Roux-En-Y Gastric Bypass: A Cross-sectional And Case-Control Study Of Post-menopausal Women

Abstract Disclosure: G. Papadakis: None. E. Gonzalez Rodriguez: None. S. Mantziari: None. J. Pasquier: None. E. Shevroja: None. N. Vionnet: None. L. Favre: None. Bariatric surgery decreases bone mineral density (BMD) due to mechanical unloading (weight loss) and secondary hyperparathyroidism linked to nutrient deficiencies (calcium, vitamin D). Most studies on the bone impact of bariatric surgery have investigated premenopausal women after a follow up of less than 3 years. In the current study, we sought to determine the long-term bone impact of Roux-en-Y gastric bypass (RYGB) on post-menopausal women. A cross-sectional and a case-control study were performed in women for whom a Dual X-ray absorptiometry (DXA) at least 3 years after surgery was available. BMD was measured at lumbar spine (LS), total hip (TH) and femoral neck (FN). Trabecular bone score (TBS) at LS was analyzed after correction for soft tissue thickness. History of fractures was inquired and DXA images were reviewed for vertebral fractures. For patients on anti-osteoporotic drugs, the DXA scan before the onset of therapy was taken into account. One-hundred nineteen women were eligible at a mean 9.0 ± 5.6 years after RYGB. The fracture rate was 12% and 6% for major osteoporotic and vertebral fractures, respectively. As calcium/vitamin D supplements were administered to all patients, serum 25-hydroxyvitamin D levels exceeded the threshold of 75 nmol/l in 77% of participants with insufficient levels (less than 50 nmol/l) only in 3 patients. Serum PTH levels were within the normal range in 87% of participants. A multivariate regression model including BMI, age, time since RYGB, one-year weight loss and serum PTH highlighted higher BMI as the sole significant predictor for better BMD at LS and TH (p=0.001 and p=0.008, respectively). Time since RYGB was the only variable inversely associated with TBS. Plasma levels of bone turnover markers (β-crosslaps, P1NP) exhibited a strong inverse correlation with BMD at all sites. For the case-control substudy, 76 post-RYGB women were age- and BMI-matched to female participants of the OsteoLaus study, a population-based cohort in Lausanne. The patient group had significantly lower BMD at all sites: LS (p=0.03), TH (p=0.01), FN (p=0.007), as well as lower TBS (p=0.003) compared to controls. No statistical difference was observed for fractures, although more major osteoporotic fractures occurred in the post-RYGB group (8 vs 4 in the controls). Possibly contributing to the bone impairment, the post-bariatric cohort had more active smokers (21 vs 7 in the controls, p=0.006) and less hormonal replacement therapy users (2 vs 12 in the controls, p=0.009). In conclusion, post-bariatric BMI is the strongest determinant of long-term BMD levels. Despite satisfactory vitamin D/PTH levels, a history of RYGB several years ago was associated with lower BMD and altered bone structure in this postmenopausal cohort. Long-term bone health monitoring is warranted after RYGB especially in women who are smoking and achieved substantial weight loss. Presentation: Friday, June 16, 2023