In clinical practice, adherence with bisphosphonate therapy varies greatly among women with osteoporosis or osteopenia. Our study suggests that better adherence with bisphosphonates confers tangible benefits in terms of graded increases in bone mineral density. Interventions to improve drug adherence should be an important component of disease management.
Introduction: In clinical trials, bisphosphonates have been found to increase bone mineral density (BMD) in women with osteoporosis or osteopenia. In clinical practice, where drug adherence is more variable, change in BMD with bisphosphonate therapy-overall and by level of adherence-is largely unknown.
Methods: A retrospective cohort study was conducted at Henry Ford Health System (Detroit, MI, USA). Study subjects were women who had low BMD at the left total hip (T-score<-1.0), began oral bisphosphonate therapy, and had ≥1 BMD measurements at the left total hip≥6 months following treatment initiation. Change in BMD was calculated between the most recent pretreatment scan and the first follow-up scan. Adherence (i.e., medication possession ratio (MPR)) was measured from therapy initiation to the first follow-up scan.
Results: Among 644 subjects, mean age was 66 years, pretreatment BMD was 0.73 g/cm2, and pretreatment T-score was -1.8. Over a mean follow-up of 27.1 months, mean MPR was 0.57 (95% CI, 0.54 and 0.59), and mean percentage change in BMD was 1.5% (1.1 and 1.9%). Within the MPR strata (five consecutive equi-intervals, from low (0-0.19) to high (0.80-1.0)), mean change in BMD was -0.8% (-1.6 and 0.1%), 0.7% (-0.3 and 1.7%), 2.1% (1.1 and 3.0%), 2.1% (1.4 and 2.9%), and 2.9% (2.3 and 3.5%), respectively. In adjusted analyses, percentage change in BMD was higher (by 1.4-3.4%, p<0.05 for all) in the highest four MPR intervals, respectively, versus MPR 0-0.19.
Conclusions: Among women with osteoporosis or osteopenia in clinical practice, better adherence with bisphosphonates appears to confer tangible benefits in terms of increases in BMD.