Is Glycemic Control Improving in U.S. Adults?

OBJECTIVE—The purpose of this study was to examine whether glycemic control has improved in recent years among individuals with diagnosed diabetes. RESEARCH DESIGN AND METHODS—We examined trends in A1C levels for adults with diagnosed diabetes using three consecutive waves of the National Health and Nutrition Examination Survey (NHANES): 1999–2000, 2001–2002, and 2003–2004. We estimated mean A1C levels and the proportion with A1C <7.0, <8.0, and <9.0%. We used multivariate regression to test whether A1C levels differed by NHANES wave after controlling for other factors. Multivariate dichotomous logistic regression and predictive margins were used to test whether the percentages of individuals with diabetes in selected A1C intervals differed by NHANES wave. RESULTS—Mean A1C levels among individuals with diagnosed diabetes declined from 7.82% in 1999–2000 to 7.47 and 7.18% in 2001–2002 and 2003–2004, respectively. After controlling for demographics and diabetes duration, A1C levels were 0.308 (P = 0.20) and 0.511 (P = 0.03) percentage points lower in 2001–2002 and 2003–2004, respectively, than in 1999–2000. The logistic results indicated corresponding improvements over time: the predictive margin for having A1C <7.0% increased from 37.0% in 1999–2000 to 49.7% in 2001–2002 and to 55.7% in 2003–2004. CONCLUSIONS—Glycemic control improved between 1999 and 2004. This trend may represent an important improvement in diabetes care and is encouraging for future reduction of diabetes-related complications.