Differences in A1C by race and ethnicity among patients with impaired glucose tolerance in the Diabetes Prevention Program.
OBJECTIVE
We sought to examine racial and ethnic differences in A1C in individuals with impaired glucose tolerance (IGT).


METHODS
We studied 3,819 individuals aged > or = 25 years with IGT who were found to be eligible to participant in the Diabetes Prevention Program. A1C was compared among five racial and ethnic groups before and after adjustment for factors that differed among groups or might affect glycemia including age, sex, education, marital status, blood pressure, adiposity (BMI and waist circumference), hematocrit, fasting and post-glucose load glucose levels, glucose area under the curve (AUC), beta-cell function, and insulin resistance.


RESULTS
Mean +/- SD A1C was 5.91 +/- 0.50%. Among whites, A1C was 5.80 +/- 0.44%, among Hispanics 5.89 +/- 0.46%, among Asian 5.96 +/- 0.45%, among American Indians 5.96 +/- 0.46%, and among blacks 6.19 +/- 0.59%. Age, sex, systolic blood pressure, diastolic blood pressure, BMI, fasting glucose, glucose AUC, corrected insulin response, and insulin resistance were each independent predictors of A1C. Adjusting for these and other factors, mean A1C levels were 5.78% for whites, 5.93% for Hispanics, 6.00% for Asians, 6.12% for American Indians, and 6.18% for blacks (P < 0.001).


CONCLUSIONS
A1C levels are higher among U.S. racial and ethnic minority groups with IGT after adjustment for factors likely to affect glycemia. Among patients with IGT, A1C may not be valid for assessing and comparing glycemic control across racial and ethnic groups or as an indicator of health care disparities.
Herman
William H
WH
Department of Internal Medicine and Epidemiology, University of Michigan Health System, Ann Arbor, Michigan, USA. dppmail@biostat.bsc.gwu.edu
Ma
Yong
Y
Uwaifo
Gabriel
G
Haffner
Steven
S
Kahn
Steven E
SE
Horton
Edward S
ES
Lachin
John M
JM
Montez
Maria G
MG
Brenneman
Tina
T
Barrett-Connor
Elizabeth
E
D000328:Adult; D044383:Black People; D001794:Blood Pressure; D003920:Diabetes Mellitus / Q000097:blood / Q000517:prevention & control; D004522:Educational Status; D005006:Ethnicity; D005260:Female; D018149:Glucose Intolerance / Q000097:blood*; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006304:Health Status; D006630:Hispanic or Latino; D006801:Humans; D007198:Indians, North American; D008297:Male; D008875:Middle Aged; D008913:Minority Groups; D044469:Racial Groups; D044465:White People
D006442:Glycated Hemoglobin