Impact of Medicare Part D on antidepressant treatment, medication choice, and adherence among older adults with depression

Abstract

Objectives: Depression in older adults is often undertreated due, in part, to medication costs. We examined the impact of improved prescription drug coverage under Medicare Part D on use of antidepressants, medication choice, and adherence.

Design, setting and participants: Observational claims-based study of older adults with depression (ICD-9: 296.2, 296.3, 311, 300.4) continuously enrolled in a Medicare managed care plan between 2004 and 2007. Three groups with limited ($150 or $350 quarterly caps) or no drug coverage in 2004-2005 obtained Part D benefits in 2006. A comparison group had stable employer-sponsored coverage throughout.

Measurements: Any antidepressant prescription fill, antidepressant choice (tricyclics or monoamine oxidase inhibitors versus newer antidepressants), and adherence (80% of days covered) in the first 6 months of treatment.

Results: : Part D was associated with increased odds of any antidepressant use among those who previously lacked coverage (odds ratio [OR] 1.61, 95% confidence interval [CI] 1.41-1.85) but odds of use did not change among those with limited prior coverage. Use of older antidepressant agents did not change with Part D. All three groups whose coverage improved with Part D had significantly higher odds of 80% of days covered with an antidepressant (OR = 1.86 [95% CI: 1.44-2.39] for no coverage, 1.74 [95% CI: 1.25%3.42] for $150 cap; and 1.19 [95% CI: 1.06-1.34] for the $350 cap groups).

Conclusions: Medicare Part D was associated with improvements in antidepressant use and adherence in depressed older adults who previously had no or limited drug coverage but not with changes in use of older agents. use and adherence in depressed older adults who previously had no or limited drug coverage but not with changes in use of older agents.

Figure 1

Flow chart describing study samples * Denominator = 200,000 individuals enrolled in study insurance plan 2004–07