THE IMPACT OF DEPRESSION ON MEDICATION ADHERENCE IN A CALIFORNIA MEDICAID POPULATION WITH CARDIOVASCULAR DISEASE

Purpose: Previous research has identified depression as a risk factor for noncompliance with medical treatment. The study objectives were 1) to investigate the association of a new depression episode with cardiovascular disease (CVD) medication adherence; 2) to assess the association of depression treatment modality with CVD medication adherence.

Method: California Medicaid (Medi-Cal) eligibility and claims data (2002-2004) were used to identify adult patients (≥18 years of age) with a diagnosis of hypertension (HYPT), coronary artery disease (CAD), and/or heart failure (HF) and at least one prescription fill for a cardiovascular medication, while data from January 1 to June 30, 2004 were used to identify patients with a new episode of depression.  CVD medication adherence was based on proportion of days covered ≥0.8 using 2004 data.  Assessment of depression treatment modality involved data from the date of diagnosis to the last day of 2004. Multiple logistic regression models were used to assess predictors of CVD medication adherence. 

Result: We identified 67,023 CVD patients, 49% with HYPT, 10% with HF, 8% with CAD, 19% with HYPT+CAD, and 14% with HF+CAD. Approximately 1.9% patients had a new episode of depression in 2004. Mean age was 66.2(SD=13.3) years. Patients with HYPT or HYPT+CAD were more likely to have depression (72%) than not (67%, p=0.003).  Only 33% of patients were adherent with CVD medication. No depression diagnosis was one of the significant factors associated with CVD medication adherence [odd ratio (OR): 1.26, 95% confidence interval (CI): 1.10-1.43]. In patients with depression, the factors associated with CVD medication adherence included a greater number of outpatient visits (OR: 1.036, CI: 1.03-1.044), greater number of cardiovascular medications used (OR: 1.51, CI: 1.33-1.72), treatment modality for depression as compared to no treatment [used both antidepressant and psychotherapy (OR: 3.16, CI: 1.80-5.57), used antidepressant only (OR: 2.04, CI: 1.44-2.90)], no hospitalization (OR: 2.49, CI: 1.70-3.66), and type of CVD (vs. HYPT) [HF+CAD (OR: 2.00,  CI: 1.27-3.14), HYPT+CAD (OR: 1.60, CI: 1.12-2.28)].  Patients adherent with antidepressants were also significantly associated with CVD medication adherence (OR: 10.99, CI: 7.00-17.24).

Conclusion: A new episode of depression and its treatment modality have significant impact on CVD medication adherence. Physician’s decision on prescribing CVD medication should consider the influence of depression on medication adherence in patients with CVD and depression.