Impact of vitamin D deficiency on bone health after Roux-en-Y gastric bypass and sleeve gastrectomy: a large propensity-matched cohort study

BACKGROUND: Vitamin D deficiency (VDD) affects 30%-70% of patients with obesity, yet its impact on postoperative bone health outcomes after metabolic surgery remains incompletely characterized. OBJECTIVES: To investigate the differential impact of Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) on postoperative bone health outcomes, both in the bariatric population with and without pre-existing VDD. SETTINGS: Analysis of TriNetX Global Collaborative Network, a deidentified real-world database from multiple institutes. METHODS: Using the TriNetX, we identified adults with obesity who underwent RYGB or SG from 2008 to 2022, with follow-up extended up to 5 years postsurgery. Propensity score matching (1:1) adjusted for baseline confounders. Primary outcomes included osteopenia, osteoporosis, and fracture-related osteoporosis. RESULTS: After matching, 35,804 patients with preoperative VDD were compared to 35,804 without. Although absolute risk differences were small, VDD patients had significantly higher odds of developing osteopenia (1.9% vs 1.0%; odds ratio [OR] 2.04, 95% confidence interval [CI] 1.79-2.32, P < .001) and osteoporosis (.7% vs .3%; OR 2.54, 95% CI 2.00-3.23, P < .001). Subgroup analyses showed elevated osteopenia risk among VDD patients undergoing RYGB (OR 1.69, 95% CI 1.41-2.02, P < .001) and SG (OR 2.02, 95% CI 1.68-2.42, P < .001), with higher osteoporosis risk in both RYGB (OR 1.94, 95% CI 1.45-2.59, P < .001) and SG (OR 1.91, 95% CI 1.36-2.67, P = .001). No significant differences in fracture-related osteoporosis were found. Postoperative labs showed persistently lower vitamin D and elevated parathyroid hormone levels in VDD patients (all P < .001). Calcium and phosphate levels were marginally higher in VDD patients. CONCLUSIONS: Preoperative VDD was linked to increased postmetabolic surgery osteopenia/osteoporosis risk. Findings support routine screening, tailored supplementation, and long-term bone monitoring. Prospective studies with standardized imaging are needed to clarify long-term skeletal outcomes.