Medication Adherence and Racial Differences in A1C Control

Diabetes Care, May 2008

OBJECTIVE—The purpose of this study was to examine medication adherence and other self-management practices as potential determinants of higher glycemic risk among black relative to white patients. RESEARCH DESIGN AND METHODS—We used a retrospective, longitudinal repeated-measures design to model the contribution of medication adherence to black-white differences in A1C among type 2 diabetic patients at a large multispecialty group practice. We identified 1,806 adult (aged ≥18 at diagnosis) patients (467 black and 1,339 white) with newly initiated oral hypoglycemic therapy between 1 December 1994 and 31 December 2000. Race was identified using an electronic medical record and patient self-report. Baseline was defined as the 13 months preceding and included the month of therapy initiation. All patients were required to have at least 12 months of follow-up. RESULTS—At initiation of therapy, black patients had higher average A1C values compared with whites (9.8 vs. 8.9, a difference of 0.88; P < 0.0001). Blacks had lower average medication adherence during the first year of therapy (72 vs. 78%; P < 0.0001). Although more frequent medication refills were associated with lower average A1C values, adjustment for adherence did not eliminate the black-white gap. CONCLUSIONS—We found persistent racial differences in A1C that were not explained by differences in medication adherence. Our findings suggest that targeting medication adherence alone is unlikely to reduce disparities in glycemic control in this setting. Further research is needed to explore possible genetic and environmental determinants of higher A1C among blacks at diagnosis, which may represent a critical period for more intensive intervention.

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Medication Adherence and Racial Differences in A1C Control

ALYCE S. ADAMS PHD CONNIE MAH TRINACTY PHD FANG ZHANG PHD KEN KLEINMAN SCD RICHARD W. GRANT JAMES B. MEIGS STEPHEN B. SOUMERAI SCD DENNIS ROSS-DEGNAN SCD E p i d e m i o l o g y / H e a l t h OBJECTIVE - The purpose of this study was to examine medication adherence and other self-management practices as potential determinants of higher glycemic risk among black relative to white patients. RESEARCH DESIGN AND METHODS - We used a retrospective, longitudinal repeated-measures design to model the contribution of medication adherence to black-white differences in A1C among type 2 diabetic patients at a large multispecialty group practice. We identified 1,806 adult (aged 18 at diagnosis) patients (467 black and 1,339 white) with newly initiated oral hypoglycemic therapy between 1 December 1994 and 31 December 2000. Race was identified using an electronic medical record and patient self-report. Baseline was defined as the 13 months preceding and included the month of therapy initiation. All patients were required to have at least 12 months of follow-up. RESULTS - At initiation of therapy, black patients had higher average A1C values compared with whites (9.8 vs. 8.9, a difference of 0.88; P 0.0001). Blacks had lower average medication adherence during the first year of therapy (72 vs. 78%; P 0.0001). Although more frequent medication refills were associated with lower average A1C values, adjustment for adherence did not eliminate the black-white gap. CONCLUSIONS - We found persistent racial differences in A1C that were not explained by differences in medication adherence. Our findings suggest that targeting medication adherence alone is unlikely to reduce disparities in glycemic control in this setting. Further research is needed to explore possible genetic and environmental determinants of higher A1C among blacks at diagnosis, which may represent a critical period for more intensive intervention. - D costly condition (1). Adverse health iabetes is a highly prevalent and events associated with diabetes include microvascular and macrovascular events. However, the risk of these and other complications of diabetes can be reduced through effective management including the use of efficacious prescription drugs (2). Diabetes is also a leading contributor to racial and ethnic disparities in health outcomes in the U.S. (3). Poorer glycemic control among blacks may be a key driver of these disparities (4). One explanation proposed for racial differences in glycemic control is lower quality of care within clinics serving predominantly black communities (5). However, improving access and overall quality of care may not reduce disparities in outcomes (6,7). Racial differences in medication adherence and other self-management practices (e.g., self-monitoring of blood glucose) have been identified in the literature (8 10). A better understanding of how medication adherence and other modifiable factors influence disparities in glycemic risk is needed to design appropriate interventions (11). To date, few studies have directly modeled the relationship between medication adherence and racial differences in A1C values among insured populations with equal access to care (12 14). The primary objective of this study was to model the relationship between medication adherence and other modifiable behaviors and A1C over time for newly treated black and white type 2 diabetic patients in a multispecialty group practice. We then compared the relative contributions of specific factors (e.g., refill adherence) to the black-white gap in A1C after adjustment. We hypothesized that racial differences in self-management practices would explain disparities in glycemic control previously identified in this insured population (15), treated in a setting in which variations in quality of care have been minimized (6). RESEARCH DESIGN AND METHODS The setting for this study was Harvard Vanguard Medical Associates, a multispecialty group practice in Massachusetts with 14 clinic sites. All patients were insured by Harvard Pilgrim Health Care. The reliability of the automated medical records system at Harvard Vanguard Medical Associates, which captures data from all ambulatory encounters, has been documented previously (16). This data source includes all ambulatory and inpatient encounters (e.g., laboratory tests, laboratory test results, prescribing information, and pharmacy contacts) in a combination of coded and narrative fields. This analysis focused on patients newly treated with oral medication therapy after their first observed diabetes diagnosis. Restricting our cohort to newly diagnosed and treated patients ensured a more homogeneous group of subjects in the initial phase of pharmacological management of hyperglycemia. Using a combination of electronic medical records and claims generated between January 1992 and December 2001, we identified 16,000 patients who had diabetes, defined as one in (...truncated)


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Alyce S. Adams, Connie Mah Trinacty, Fang Zhang, Ken Kleinman, Richard W. Grant, James B. Meigs, Stephen B. Soumerai, Dennis Ross-Degnan. Medication Adherence and Racial Differences in A1C Control, Diabetes Care, 2008, pp. 916-921, 31/5, DOI: 10.2337/dc07-1924