Date of Award

1-1-2012

Document Type

Campus Access Dissertation

Department

Health Services and Policy Management

First Advisor

Sudha Xirasagar

Abstract

Background: Stroke is the third leading cause of mortality and affects about 800.000 adults each year. Diabetes is a major stroke risk factor, and stroke mortality is doubled if diabetes is present. The empirical causal relationship between stroke and glycemic control remains speculative, although cross sectional and attributed associations are documented. This study uses a national population-based 10-year, longitudinal dataset from a single payer, nationwide universal coverage, single health plan system with low copayments and almost no access barriers to address this important knowledge gap. Finding significant stroke risk reduction with medication adherence can motivate diabetes patients for high adherence and motivate providers and health plans to aggressively pursue medication adherence among patients and dramatically reduce stroke morbidity, mortality and costs. Objective: To examine whether long-term hazard among type 2 diabetes patients is reduced by high adherence to antidiabetic medication.

Methods: An all-medical care claims merged database of all patients with a diabetes diagnosis 2000-2009 was used. Newly diagnosed diabetes patients, diagnosed between 2000 and 2008, followed up through 2009, 43,034 patients who suffered stroke 1+ years after diagnosis, and 173,468 matched controls (1:4) on month of diabetes diagnosis, age group and gender, who had at least one prescription filled for antihyperglycemic medication in the year prior to stroke/pseudo-event for matched controls, the stroke date of their stroke match. Adherence was measured as Proportion of Days Covered (PDC) by antihyperglycemic medication Time dependent proportional hazard regression was used to model stroke hazard ratio using PDC (≥0.8, 0.4-0.79, <0.4) and Charlson Comorbidity counts (≤2, 3-5, 6+) as time dependent variables adjusting for age, gender, Defined Daily Dose (DDD) measure of diabetes severity, hypertension, hyperlipidemia, urbanization, treating physician specialty, medical facility level, Diabetes Care Management Program participation.

Results: Stroke hazard ratio per year since diagnosis was 1.09 for PDC<0.4 and 1.05 for 0.45 and 3-5 comorbidities vs. <2 group, translating into 1.41 and 1.25 in Year 9.

Conclusion: Medication adherence yields rich stroke reduction benefits, cutting stroke risk several times over when hazards in all years are added. The beneficial effect exceeds the risk from factors beyond patient control namely co-morbidities. Participation in diabetes care program cut the risk in half.

Rights

© 2012, Chuan-Song Wu

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