Proportion of Osteoporotic Women Remaining at Risk for Fracture Despite Adherence to Oral Bisphosphonates

Abstract

Background

Adherence to oral bisphosphonates is often low, but even adherent patients may remain at elevated fracture risk. The goal of this study was to estimate the proportion of bisphosphonate-adherent women remaining at high risk of fracture.

Methods

A retrospective cohort of women aged 50 years and older, adherent to oral bisphosphonates for at least two years was identified, and data were extracted from a multi-system health information exchange. Adherence was defined as having a dispensed medication possession ratio ≥ 0.8. The primary outcome was clinical occurrence of: low trauma fracture (months 7–36), persistent T-score ≤ − 2.5 (months 13–36), decrease in bone mineral density (BMD) at any skeletal site ≥ 5%, or the composite of any one of these outcomes.

Results

Of 7435 adherent women, 3110 had either pre- or post-adherent DXA data. In the full cohort, 7% had an incident osteoporotic fracture. In 601 women having both pre- and post-adherent DXA to evaluate BMD change, 6% had fractures, 22% had a post-treatment T-score ≤ − 2.5, and 16% had BMD decrease by ≥ 5%. The composite outcomes occurred in 35%. Incident fracture was predicted by age, previous fracture, and a variety of co-morbidities, but not by race, glucocorticoid treatment or type of bisphosphonate.

Conclusion

Despite bisphosphonate adherence, 7% had incident osteoporotic fractures and 35% had either fracture, decreases in BMD, or persistent osteoporotic BMD, representing a substantial proportion of treated patients in clinical practices remaining at risk for future fractures. Further studies are required to determine the best achievable goals for osteoporosis therapy, and which patients would benefit from alternate therapies.