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Health Services Research & Development

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2011 HSR&D National Meeting Abstract

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2011 National Meeting

1007 — The Impact of Comorbid Depression on Longitudinal Medication Adherence among Veterans with Type 2 Diabetes

Axon RN (Charleston REAP), Mauldin PD (Charleston REAP), Gebregziabher M (Charleston REAP), Echols C (Charleston REAP), Gilbert GE (Charleston REAP), Hunt KJ (Charleston REAP), Lynch C (Charleston REAP), Egede LE (Charleston REAP)

Prior research suggests that comorbid depression is associated with poorer glycemic control and higher mortality among individuals with diabetes, and medication adherence has been implicated as a potential mediator of this effect. In order to better understand the relationship between depression and medication adherence as measured by medication possession ratio (MPR), we performed a retrospective analysis of a national cohort of Veterans with type 2 diabetes.

A national cohort of veterans with type 2 diabetes was created by linking multiple patient and administrative files from the VA National Patient Care Database (NPCD) and the VA Pharmacy Benefits Management (PBM) database. The cohort included 690,968 veterans with diabetes who were followed over a 5 year period. The main outcome measure was medication adherence (MPR 80.0% indicating good adherence). We fit logistic regression using generalized estimating equations (GEE) with medication adherence as the dependent variable and depression (1 = yes, 0 = no) as the main independent variable, with adjustment for potential confounders.

The study population consisted of veterans receiving prescriptions for insulin or oral hypoglycemic agents (VA classes HS501 or HS502, respectively) in 2002 who were followed until death, loss to follow-up, or through December 2006. The study population was 72.9% non-Hispanic White, 12.9% non-Hispanic Black, 5.1% Hispanic and 9.2% Other/Missing/Unknown racial/ethnic group, with a mean age 65.8 ± 11.2 years in 2002. Depression was negatively associated with medication adherence over time (OR 0.89 (95% CI: 0.88, 0.91). After adjusting for demographic and comorbidity factors, depression remained negatively associated with medication adherence over time (OR 0.94 (95% CI: 0.92, 0.95) indicating that depression is an independent contributor to poor medication adherence, and that these effects persist over time.

Patients with a history of depression had 6% lower odds of having good medication adherence over 5 years of follow-up in a national sample of veterans with type 2 diabetes compared to those without a history of depression.

This study provides new data regarding the longitudinal effects of depression on medication adherence, and suggests that aggressive recognition and treatment of depression in veterans with diabetes will likely result in better adherence and improved outcomes.

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