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Background: Black patients with diabetes are at elevated risk for poor glycemic control. This study assessed the relative importance of improving medication adherence as a strategy for reducing the black-white gap in HbA1c control. Methods: We used a retrospective, longitudinal repeated measures design to model the temporal relationship between medication adherence and racial differences in HbA1c in a managed care setting. We identified 2,099 (black=564, white=1535) insured adult diabetes patients newly treated on oral hypoglycemic therapy between 01/01/94 and 12/31/00. We used hierarchical mixed models with multiple imputation to estimate (1) the impact of medication adherence on the black-white gap in HbA1c control and (2) HbA1c by race. Results: At baseline, black patients had higher HbA1c values compared to whites (9.8 vs. 8.9; p<0.05). Black patients were consistently 7% less adherent to oral medications over time. In stratified models, tighter medication adherence was associated with better HbA1c control among all patients [whites: -0.23 (-0.20, -0.16); blacks: (-0.18 (-0.32, -0.03)]. However, better adherence (>75%) resulted in only a slight reduction (-0.02%) in the black-white gap. Frequent self-monitoring and insulin use had clinically and statistically significant impacts on HbA1c, particularly among black patients (SMBG: -0.65% (-1.04, -0.26); insulin: -0.18 (-0.32, -0.03)).Conclusions: The black-white gap in HbA1c was largely determined by fixed (e.g., age) and unmeasured (e.g., biological) factors. However, better adherence, more frequent self-monitoring, and insulin use were all highly predictive of lower HbA1c levels. Improving medication adherence is an important goal for all patients, but is unlikely as a single strategy to reduce the black-white gap in glycemic control in this setting. [ABSTRACT FROM AUTHOR]

Adherence to hypoglycemic medications is often suboptimal. Adherence differences may contribute to health disparities for black diabetes patients, including higher complication rates, greater complication-related disability, and higher mortality. In this longitudinal retrospective study, we assessed black-white differences in long-term adherence to hypoglycemic therapy among newly diagnosed diabetes patients in a managed care setting where all members had prescription drug coverage. Our study cohort included 1909 newly diagnosed adult diabetes patients (26% black and 74% white) who initiated hypoglycemic therapy and received continuous care within 14 health centers of a large multi-specialty care group practice in the Boston area. Using 10 years of computerized medical record and claims data, we used longitudinal survival methods and generalized estimating equations to examine racial differences in (1) incidence of hypoglycemic therapy (time from diabetes diagnosis until first hypoglycemic therapy), (2) time until discontinuation of hypoglycemic therapy from first prescription, and (3) long-term adherence (amount dispensed versus amount prescribed) over a 24-month follow-up from first hypoglycemic prescription. We found that black patients were as likely as whites to initiate oral therapy but experienced higher rates of discontinuation with their medication (HR: 1.8, 95% CI: 1.2, 2.7) and were less adherent over time. These black-white differences increased over the first 6 months of therapy but stabilized thereafter for patients initiated on sulfonylurea. Significant black-white differences in adherence levels were constant throughout follow-up for patients initiated on metformin. Racial differences in adherence to hypoglycemic persist even with equal access to medication. Unequal adherence may contribute to racial disparities in diabetes outcomes. Early and aggressive emphasis on sustaining medication use after initiation of medication may lead to improved adherence to hypoglycemic medication and may potentially reduce persistent racial differences in self-management practice and clinical outcomes. [ABSTRACT FROM AUTHOR]