Firstly, we would like to point to the fact that our study had the highest period for post-bariatric surgical follow up of 8.6 years among the other published studies. In this single-centre case–control study, the risk of fracture in patients with obesity who underwent bariatric surgical intervention, mainly sleeve gastrectomy, was significantly higher at 2.7-folds comparing with age and gender-matched patients with obesity managed with weight reduction therapy. Nevertheless, the vast majority of the fractures were not typical for osteoporotic fragility fracture in both groups. These data pointed to negative sequelae of bariatric procedures on bone health in the long term which needs to be addressed. Post-bariatric surgery data gave no consistent results, but more data is pointing towards increasing the risk of fractures [6,7,8,9, 14,15,16]. These studies differed with the type of bariatric procedures and duration of follow-up (Appendix Table 6 summarized these studies).
As compared to previous studies, our study revealed the highest fracture risk in our surgical group with an OR of 2.71. We think this could be because our surgical intervention group had more history of previous fractures with proton pump and antiepileptics use as compared to controls. However, this could be counteracted by the fact that controls are more likely to be on steroids.
Two UK retrospective studies in 2012 and 2015 did not show a statistically significant increment in fracture risk [6, 7], and we think this could be due to the relatively short follow-up period of 3 years. Lu et al. (2015), from Taiwan, revealed a significantly increased risk of fractures at only 1.2-folds and a slightly longer mean follow-up duration of 4.8 years as compared to the above UK studies. The sub-analysis of this study revealed that the relative risk of fracture is significantly more for the malabsorptive procedure (HR: 1.47, 95% CI 1.01–2.15) and not for the restrictive procedures (HR 1.17, 95% CI 0.97–1.41). However, the study was not powered to show the difference between malabsorptive and restrictive procedures .
Rousseau et al. (2016) conducted the largest ever study in this area with 12, 676 patients in the bariatric surgery group and a matched 38, 028 obese patients who undergone a non-surgical intervention and 12, 6760 non-obese patients. Fracture risk increased significantly by 1.8-folds in the surgical group vs 1.13 in the obese non-surgical group in comparison with non-obese subjects . In this study, the mean follow-up duration was only 4.4 years (Appendix Table 6).
We think the longer the duration for the follow-up, the more likely will be the increased risk for the fracture, and this has been demonstrated very well in our study and from the above discussion.
Whether fracture risk differs by the type of bariatric procedure was investigated by Yu et al. (2017), the conclusion was that Roux-en-Y gastric bypass was associated with a 43% (HR1.43, 95% CI 1.13–1.81) increment in risk of non-vertebral fracture compared with adjustable gastric banding . A meta-analysis ran by Zhang et al. (2018) showed a significant increase in non-vertebral fracture risk with RR 1.42. Sub-group analysis showed mixed surgical procedures (mixture of restrictive and malabsorptive procedure) compared with restrictive surgical procedure trended to have a higher fracture risk, but this finding was not statistically significant (RR 1.54, 95% CI 0.96–2.46) . Our strength for the study came from the fact that we have a reasonable number of the patient as calculated by sample size and the long duration of the follow-up (8.6 years). It also came from the Middle East where there is a paucity of data and where the population differs from the Western populations (R1 and R2).
The Limitations of our Study
The surgical group was not BMI matched to the control group, which is understandable. This is important as it is well known that the higher the BMI, the more the fracture risk [8, 17,18,19]. In our study, the median BMI at the time of fracture was comparable between the surgical and control groups (36.17 vs 35.98). We also found that our surgical group is more likely to have previous fractures and be on proton pump inhibitors and antiepileptics as compared to controls, and that on contrary, controls are more likely to be on steroids which could affect our results. Smoking, alcohol consumption data, and other comorbidities that can affect bone health were missing in the majority of our patients, which we think could be important cofounders for fracture risk. Sub-clinical vertebral fractures were not included in the outcome, which could underestimate the fracture rate. Most of the fractures in our cohort are not a typical osteoporotic site for fracture; however, these results are pointing to negative sequelae on bone health in general, particularly in the first 4-yearspost-bariatric intervention. This highlights the importance of adherence to post-bariatric procedure recommendations like vitamins, minerals, and proteins supplements and to consider some intervention to counteract such risk. Lastly, we recommend that any future study in this respect should be prospective with consideration of the possible confounders and long enough to answer these important questions.