Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Osteoporosis Medication Adherence and Fracture Risk among Women in a Large U.S. Health Plan.

Viswanathan1,  Hema, Wade5,  Sally W., Curtis4,  Jeffrey R., Yu3,  Jingbo, White6,  Jeffrey, Stolshek2,  Bradley, Merinar2,  Claire

Amgen Inc., Thousand Oaks, CA
Amgen Inc.
HealthCore, Inc.
University of Alabama at Birmingham
Wade Outcomes Research and Consulting
WellPoint, Inc.

Purpose:

Osteoporosis (OP) poses a significant economic and clinical burden. Low adherence may mitigate treatment efficacy, including fracture risk reduction. This study examined the association between OP medication adherence during the first year on therapy and subsequent fracture risk using recent data from a commercially insured population.

Methods:

Female patients were identified from a large, commercially insured U.S. population with integrated pharmacy and medical claims. Patients were included if they were >= age 45, new to OP therapy (no OP medication claims in prior year) with first (index) OP medication claim between 1/1/2005 and 4/30/2008, and had continuous coverage for >= 12 months pre- and post-index. Patients were excluded if they had: pre-index Paget's disease or malignant neoplasm, or were in a skilled nursing facility, or on multiple OP medications at index. Clinically-diagnosed and coded fractures were identified using published claims criteria. Patients who had a fracture in the first year on therapy were excluded. This ensured that the time periods for assessing exposure (medication) and outcome (fracture) did not overlap. Logistic regression was used to assess the association between the medication possession ratio (MPR: < 0.5, 0.5 to 0.8, > 0.8) during the 12 months post-index and fracture risk thereafter in bisphosphonate users. Covariates included baseline demographic and clinical characteristics including comorbidities and prior fracture.

Results:

The analysis included 35,958 patients who were new to OP therapy, had a mean age (± SD) of 59.4 ± 9.2 years (range: 45 to 102 years), and had a mean post-index follow up of 834.3 days. At index, 99.6% of patients used a bisphosphonate. Over 12 months post-index, the mean MPR was 0.57 (95% CI: 0.57, 0.58). Mean 12-month MPR was lower among patients with fracture (N = 1,006) compared with those without fracture (N = 34,952; 0.54 vs 0.57, respectively; p < 0.001). Patients were clustered at the upper and lower ends of the MPR range. In multivariate modeling, bisphosphonate users with a MPR > 0.8 (N = 12,318) over 12 months had a 18% lower risk of subsequent fracture compared with those with a MPR < 0.5 (N = 13,878), even after controlling for demographic characteristics, insurance type, prior fracture, select comorbidities, and other potential confounders (p = 0.007; Table).

Table. Adjusted Fracture Risk by Level of Adherence Among Female Bisphosphonate Users*

Medication Possession Ratio (MPR)Number of PatientsOdds Ratio for Fracture95% Confidence Intervalp-value
<0.513,878ReferenceNANA
0.5 to 0.85,2330.8050.668, 0.9710.023
>0.812,3180.8220.713, 0.9470.007
* Adjusted for demographic characteristics, insurance type, prior fracture, select comorbidities, and other potential confounders

Conclusion:

In this study, female patients in a large, commercial health plan had a mean 12-month MPR of 0.57 for OP medications. Women with low adherence (MPR < 0.5) experienced an increased fracture risk even after controlling for a large number of fracture-related covariates.

To cite this abstract, please use the following information:
Viswanathan, Hema, Wade, Sally W., Curtis, Jeffrey R., Yu, Jingbo, White, Jeffrey, Stolshek, Bradley, et al; Osteoporosis Medication Adherence and Fracture Risk among Women in a Large U.S. Health Plan. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :1552
DOI: 10.1002/art.29318

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