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Health Services Research & Development

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2008 HSR&D National Meeting Abstract

National Meeting 2008

3023 — Adherence to Oral Hypoglycemic Medications among VA Patients with Schizophrenia and Type 2 Diabetes

DIXON LB (VA VISN 5 MIRECC and University of Maryland School of Medicine), MCCARTHY JF (VA SMITREC and University of Michigan), SOLIMAN S (University of Michigan), VALENSTEIN M (VA SMITREC and University of Michigan)

Relative to the general population, individuals with schizophrenia have higher rates of co-occurring medical conditions, such as Type 2 diabetes, and poorer associated health outcomes. To evaluate whether psychiatric illness confers specific disadvantages in diabetes self-management, we compared adherence to oral hypoglycemic medications between diabetes patients with versus without schizophrenia.

Using the VA’s National Psychosis Registry, we identified all patients with schizophrenia and Type 2 diabetes diagnoses in FY2002 who filled at least one oral hypoglycemic prescription (N=11,477). From a random sample of all VA patients in FY2002, we identified a comparison group of patients with diabetes but without schizophrenia (N=10,808). We used the Medication Possession Ratio (MPR) as an objective measure of medication adherence in FY2003, calculated by dividing the days' supply of oral hypoglycemics that was dispensed by the number of days' supply needed to take the medication continuously. We operationalized nonadherence as having an MPR < 0.8, indicating receipt of less than 80% of needed medications.

Over one year, nonadherence was less prevalent among diabetes patients with schizophrenia (43%) than those without schizophrenia (51%; p < 0.001). In multivariable regression analyses, diabetes patients with schizophrenia were 27% less likely than patients without schizophrenia to be nonadherent (AOR: 0.73; 95% CI: 0.68-0.78). Patient characteristics associated with poorer adherence included African-American race, homelessness, substance use disorder, depression, greater medical co-morbidity, greater prescription copayments, and receipt of prescriptions with < 30 days’ supply. Having more outpatient visits and having a higher proportion of prescriptions delivered by mail were associated with better adherence.

Among patients actively engaged in care, fewer VA patients with schizophrenia and diabetes than without schizophrenia were nonadherent to oral hypoglycemic medications. However, adherence was worrisome in all patients. Whether co-management of a chronic psychiatric illness, contact with mental health providers, or other factors bestows benefits for diabetes self-management in persons with schizophrenia merits continued investigation.

These data indicate that all patients with diabetes require additional support to improve or maintain medication adherence. Current treatment practices for patients with schizophrenia, such as regular system contacts, may increase adherence among all patients.

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