Medication Adherence Does Not Explain Black-White Differences in Cardiometabolic Risk Factor Control among Insured Patients with Diabetes.
BACKGROUND
Among patients with diabetes, racial differences in cardiometabolic risk factor control are common. The extent to which differences in medication adherence contribute to such disparities is not known. We examined whether medication adherence, controlling for treatment intensification, could explain differences in risk factor control between black and white patients with diabetes.


METHODS
We identified three cohorts of black and white patients treated with oral medications and who had poor risk factor control at baseline (2009): those with glycated hemoglobin (HbA1c) >8 % (n = 37,873), low-density lipoprotein cholesterol (LDL-C) >100 mg/dl (n = 27,954), and systolic blood pressure (SBP) >130 mm Hg (n = 63,641). Subjects included insured adults with diabetes who were receiving care in one of nine U.S. integrated health systems comprising the SUrveillance, PREvention, and ManagEment of Diabetes Mellitus (SUPREME-DM) consortium. Baseline and follow-up risk factor control, sociodemographic, and clinical characteristics were obtained from electronic health records. Pharmacy-dispensing data were used to estimate medication adherence (i.e., medication refill adherence [MRA]) and treatment intensification (i.e., dose increase or addition of new medication class) between baseline and follow-up. County-level income and educational attainment were estimated via geocoding. Logistic regression models were used to test the association between race and follow-up risk factor control. Models were specified with and without medication adherence to evaluate its role as a mediator.


RESULTS
We observed poorer medication adherence among black patients than white patients (p < 0.01): 50.6 % of blacks versus 39.7 % of whites were not highly adherent (i.e., MRA <80 %) to HbA1c oral medication(s); 58.4 % of blacks and 46.7 % of whites were not highly adherent to lipid medication(s); and 33.4 % of blacks and 23.7 % of whites were not highly adherent to BP medication(s). Across all cardiometabolic risk factors, blacks were significantly less likely to achieve control (p < 0.01): 41.5 % of blacks and 45.8 % of whites achieved HbA1c <8 %; 52.6 % of blacks and 60.8 % of whites achieved LDL-C <100; and 45.7 % of blacks and 53.6 % of whites achieved SBP <130. Adjusting for medication adherence/treatment intensification did not alter these patterns or model fit statistics.


CONCLUSIONS
Medication adherence failed to explain observed racial differences in the achievement of HbA1c, LDL-C, and SBP control among insured patients with diabetes.
School of Medicine, Virginia Commonwealth University, Richmond, VA, USA. jelstonlafat@vcu.edu.|Henry Ford Health System, Detroit, MI, USA. jelstonlafat@vcu.edu.|Department of Social and Behavioral Health, Virginia Commonwealth University, PO Box 980149, Richmond, VA, 23298, USA. jelstonlafat@vcu.edu.
Jennifer Elston
JE
Lafata
Division of Research, Kaiser Permanente Northern California, Oakland, CA, USA.
Andrew J
AJ
Karter
HealthPartners Institute for Education and Research, Minneapolis, MN, USA.
Patrick J
PJ
O'Connor
University of Florida, Gainesville, FL, USA.
Heather
H
Morris
Division of Research, Kaiser Permanente Northern California, Oakland, CA, USA.
Julie A
JA
Schmittdiel
School of Medicine, Virginia Commonwealth University, Richmond, VA, USA.
Scott
S
Ratliff
Group Health Research Institute, Seattle, WA, USA.
Katherine M
KM
Newton
Kaiser Permanente Colorado Institute for Health Research, Denver, CO, USA.|University of Colorado Skaggs School of Pharmacy and Pharmaceutical Sciences, Aurora, CO, USA.
Marsha A
MA
Raebel
Marshfield Clinic, Marshfield, WI, USA.
Ram D
RD
Pathak
Lutheran HealthCare, Brooklyn, NY, USA.
Abraham
A
Thomas
Kaiser Permanente Georgia Center for Health Research- Southeast, Atlanta, GA, USA.
Melissa G
MG
Butler
Department of Research and Evaluation, Kaiser Permanente Southern California, Los Angeles, CA, USA.
Kristi
K
Reynolds
Kaiser Permanente Hawaii, Center for Health Research - Hawaii, Honolulu, HI, USA.
Beth
B
Waitzfelder
Kaiser Permanente Colorado Institute for Health Research, Denver, CO, USA.
John F
JF
Steiner
D000293:Adolescent; D000328:Adult; D001741:Black or African American / Q000523:psychology* / Q000706:statistics & numerical data; D000368:Aged; D001794:Blood Pressure / Q000502:physiology; D002318:Cardiovascular Diseases / Q000208:ethnology* / Q000517:prevention & control; D008078:Cholesterol, LDL / Q000097:blood; D003920:Diabetes Mellitus / Q000097:blood / Q000188:drug therapy / Q000208:ethnology* / Q000523:psychology; D005260:Female; D005500:Follow-Up Studies; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D008297:Male; D055118:Medication Adherence / Q000208:ethnology*; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D012959:Socioeconomic Factors; D014481:United States; D044465:White People / Q000523:psychology* / Q000706:statistics & numerical data; D055815:Young Adult; D016903:Drug Monitoring
D008078:Cholesterol, LDL; D006442:Glycated Hemoglobin
cardiometabolic risk factors; diabetes care; medication adherence; racial disparities