Cost and consequences of noncompliance with osteoporosis treatment among women initiating therapy.

Objective: The objective was to evaluate compliance with osteoporosis (OP) treatments and determine the fracture and healthcare burden associated with noncompliance.

Methods: This retrospective analysis of a US claims database identified women initiating an OP medication from 1 January 2002 to 30 June 2009. Patients were ≥55 years and had ≥1 pharmacy claim for a bisphosphonate or non-bisphosphonate (raloxifene, calcitonin, teriparatide); the index date was the first pharmacy claim. There were three study periods: baseline (12 months pre-index); compliance period (0-12 months post-index); and follow-up period (12-24 months post-index). Medication possession ratio (MPR) was calculated during the compliance period to differentiate two cohorts: compliant (MPR ≥ 80%) and noncompliant (MPR < 80%). Outcomes during follow-up were modeled by logistic regression (presence of fracture), Poisson regression (healthcare utilization incidence rate) and gamma regression (healthcare costs), all adjusted for patient demographic and clinical characteristics.

Results: Overall, 685,505 women initiating OP therapy were identified and 57,913 (8.4%) met the inclusion criteria: only 23,430 (40.5%) were compliant and 34,483 (59.5%) were noncompliant. Mean age was 64 years. Noncompliance was associated with a 20% higher risk of any fracture (odds ratio: 1.20, 95% CI = 1.07-1.35), a higher incidence rate ratio (IRR) for inpatient utilization (IRR: 1.26, 95% CI = 1.19-1.34) and a lower rate of outpatient utilization (IRR: 0.97, 95% CI = 0.95-0.98). Noncompliant patients had 13% higher medical costs (cost ratio: 1.13, 95% CI = 1.06-1.21) than compliant patients.

Limitations: Inclusion in this study required 36 months of continuous healthcare coverage. Thus, the results are primarily applicable to a stable, managed care population and may not be generalizable to other populations.

Conclusion: Noncompliance with OP therapy was associated with a higher risk of fracture, higher all-cause medical costs and a higher frequency of inpatient service utilization. Additional research is needed to identify barriers to compliance with OP therapy.