Men's Osteoporosis Support Group

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Bisphosphonate compliance and fracture risk

Bone. 2008 Sep 26. [Epub ahead of print], Effectiveness of bisphosphonate therapy in a community setting. Feldstein AC, and others. PMID: 18926939. This retrospective cohort study used a matched design that compared time to clinical fracture in at-risk community women who initiated a bisphosphonate medication between 7/1/1996 and 6/30/2006 to those who did not. The study involved 1829 Eligible Washington and Oregon HMO members who were newly treated women aged >/=55 years with either a BMD T-score of </=-2.0 or a prior qualifying clinical fracture. The same number of controls were used. The primary outcome was the first new incident fracture validated through chart review. Only about 45% of treated patients had a bisphosphonate medication possession ratio (MPR) of >/=0.80. During follow-up, 198 (10.8%) of patients in the treated group had incident fractures, vs. 179 (9.8%) of patients in the comparison group. The authors concluded, "In this analysis of a community cohort of post-menopausal women at risk, the fracture risk of patients who received bisphosphonates did not differ significantly from those who did not. (Editor's emphasis) An enhanced understanding of this lack of treatment effect is urgently needed."

Editor's comments. In another Update I discuss articles that show the importance of a high degree of compliance (taking your medications on the prescribed schedule in the prescribed dosage). In fact if compliance was greater that 80%, this doubled the fracture reduction. Thus in the Feldstein and others study, with the low incidence of compliance, we would expected reduced improvement in fracture reduction. But to get none at all is problematic. Hopefully further investigation will shed light on this question. There is another recent study regarding compliance and fracture reduction to which I'll present next.

Curr Med Res Opin. 2008 Oct 14. [Epub ahead of print]. Relationship between duration of compliant bisphosphonate use and the risk of osteoporotic fractures. Meijer WM and others. PMID: 18922215. This study involved at total of 14,760 women who were new bisphosphonate users aged >/= 45 years or with diagnosed post-menopausal osteoporosis in the period of January 1996 - June 2004. The authors investigated the relationship between duration of compliant bisphosphonate use and the risk of osteoporotic fracture. Compliance was defined as >/= 80% possession ratio of bisphosphonate. Results showed 387 fracture patients fulfilled the inclusion criteria. When compared to controls, increasing duration of compliant bisphosphonate use was associated with a decreased risk of fracture (trend p < 0.01). The authors founds that 1-2 years of compliant bisphosphonate use and 3-4 years of compliant bisphosphonate use decreased fracture risk by 12% and 46%, respectively, compared to < 1 year of compliant bisphosphonate use. Unexpectedly, 5-6 years of compliant bisphosphonate use was no longer associated with a decreased risk of fractures compared to < 1 year of compliant bisphosphonate use. The authors conclude, "These results show a direct link between duration of compliant bisphosphonate use and fracture risk, and confirm the importance of continuing the use of bisphosphonates to maintain optimal bone protection. However, this link is inconclusive for bisphosphonate use for more than 4 years."

Editor's comments. This study found the more traditional and expected result that the higher the degree of compliance the greater the reduction in fracture risk, particularly for the first four years. However, unexpectedly, it also found no decrease in fracture risk after 5-6 years of compliant bisphosphonate use when compared to < 1 year of compliant bisphosphonate use. This result is puzzling and I hope further studies will shed light on it.

Here is another recent Update with additional information on compliance that you might find helpful. Overall it is important to take osteoporosis medication in a compliant manner if one expects to get effective fracture reduction. Another Update that might have bearing on these results highlights a study that found that stopping alendronate (Fosamax) after five years of therapy had no effect on fracture rate over the next five years. So it just might be that after a few years on a bisphosphonate such as Fosamax, Actonel or Boniva, a person maxes out on fracture risk improvement, possibly because bone mineral density (BMD) has improved to the point where medications simply can't decrease the risk of fracture further. And since the bisphosphonates have such a long half-life (at least ten years), even though you stop taking them, they are still influencing BMD for a long time after cessation. I suspect we'll be hearing a lot more on this topic with time.

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