SAT-540 Bisphosphonates and Fracture Incidence in Young Adults

Introduction: Osteoporosis and its treatment have widely been studied in postmenopausal women. In contrast, limited evidence on osteoporosis and its treatment exists for the younger adults. Determining whether bisphosphonates truly help reduce fracture risk in the younger population can have profound effects on their quality of life and reduce overall healthcare costs. The objective of our study is to assess whether exposure to bisphosphonates reduces fracture incidence in a younger population (age 19-40 years) in a 5-year follow up period. Methods: This is a Retrospective cohort study where the Kaiser Permanente electronic health records were used to search for patients of age 19-40 with abnormal bone density (either Z-score < -2 or T-Score < -2.5). Age matched controls consisted of a population with no bisphosphonate exposure or exposure less than six months (n=358). The treatment cohort consisted of those started on bisphosphonate therapy for a minimum of 6 months within 4 years of their first Dual-energy X-ray absorptiometry (DXA) (n=64). We compared the subsequent incidence of fracture of both groups as well as time to fracture to see if there was a significant difference between the two groups. over the 5-year follow up period. Comparisons were analyzed with chi-square for categorical variables and Wilcoxon rank sum test for continuous variables. Results: 422 patients were identified with abnormal bone density. 64 were found to have bisphosphonates exposure. Fracture occurred in 32 (9.8%) patients in the control group. 6 (10.3%) patients were found to have fracture in the treatment group. T-score were noted to be -2.3±0.80 and -2.53±0.58 for the control and treatment group respectively. Using multivariable logistic regression, no significant differences were found between groups in total fractures (Hazard ratio (HR) 1.54 (95% confidence interval (CI) 0.26-6.26)). Similarly, no correlation was noted between the length of bisphosphonate therapy and fracture incidence (Odds ratio (OR) 0.996 (95% CI 0.966-1.026)). Conclusion: Several studies have shown the reduction of fracture incidence with the use of bisphosphonates in postmenopausal women. Our study investigated their effects in young adults. No significant differences in total fracture incidence were noted between groups. Although lower T-scores were noted in the treatment group, we didn't find a correlation between T-score and fracture risk. This finding may suggest that there is a variation in the pathophysiology of low bone density in young adults such that they don't have bone resorption or true osteoporosis. This could be one of the reasons why standard therapy for osteoporosis may not have shown benefits in our treatment group. Further research into the pathophysiology of low bone density in young adults and what specific etiologies would benefit from antiresorptive therapy may be needed for more definitive conclusions.