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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.
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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)