Introduction: Bariatric surgery may have detrimental effects on bone health. We investigated the long-term effects of bariatric surgery on bone health to delineate whether they differed by procedure type.

Methods: The records of patients who had undergone either sleeve gastrectomy (SG) or Roux-en-Y Gastric Bypass (RYGB) surgery with a follow up period of 2 years were reviewed. Comparison was made between blood assays (vitamin D, parathormone, calcium, phosphate and magnesium) and aerial bone mineral density (aBMD) measured at baseline with measurements made at 6, 12, 18 and 24 months post-operatively. History of fractures was also recorded.

Results: There were 1309 in the SG group and 1132 patients in the RYGB group. There was a gradual decrease in vitamin D, calcium, phosphate and magnesium and increase in parathormone levels peaking at 18 months in both groups (P<0.05). There was also reduction in aBMD over time being greater at 24 months and most marked in the total hip and full body measures (p<0.05). This correlated to amount of weight loss. All changes were more in RYGB (p<0.05) where there was also a higher number of post-operative fractures (p<0.05).

Conclusion: Bariatric surgery is associated with gradual decline in bone health and increased fracture risk peaking at 18 months after surgery. This effect is more prominent with RYGB (combined restrictive and malabsorptive) procedures as opposed to SG (restrictive only) surgeries. It is imperative to counsel patients about increased bone fragility and fracture risk prior to making the choice of bariatric surgery.