Diabetes Care Publish Ahead of Print, published online October 12, 2007
Is Glycemic Control Improving in U.S. Adults? Thomas J. Hoerger, PhD,1 Joel E. Segel, BA,1 Edward W. Gregg, PhD,2 Jinan B. Saaddine, MD2 1
2
RTI International, Research Triangle Park, NC Centers for Disease Control and Prevention, Atlanta, GA
Address correspondence and reprint requests to: Thomas J. Hoerger Director RTI-UNC Center of Excellence in Health Promotion Economics RTI International 3040 Cornwallis Road P.O. Box 12194 Research Triangle Park, NC 27709 E-mail:
[email protected]
Received for publication 9 August 2007 and accepted in revised form 9 October 2007.
1 Copyright American Diabetes Association, Inc., 2007
ABSTRACT Objective: To examine whether glycemic control has improved in recent years among persons 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 less than 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 persons with diabetes in selected A1c intervals differed by NHANES wave. Results: Mean A1c levels among persons 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 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 diabetesrelated complications.
2
M
glycemic control in clinical disease management and public health programs during the past decade, these observations are both concerning and surprising. In this study, we examined recent national trends in glycemic control among adults with diagnosed diabetes.
ajor randomized controlled trials conducted during the 1990s demonstrated the importance of tightly and consistently managing A1c levels among type 1 and type 2 diabetes patients (1,2). A follow-up of the Diabetes Control and Complications Trial (DCCT) reaffirmed the value of glycemic control, since microvascular complications remained lower among intervention participants seven years after the trial concluded (3). These and other studies highlighted the central role of glycemic control in the management of diabetes. Accordingly, professional associations, including the American Association of Clinical Endocrinologists (AACE), the American Diabetes Association (ADA), and the European Association for the Study of Diabetes (EASD), established clinical guidelines in the range of 6.5-7.0% to motivate health professionals and patients to consistently manage blood glucose levels (4,5). The National Diabetes Quality Improvement Alliance, a private-public entity, developed national performance measures to monitor glycemic control and other diabetes care processes and outcomes. Despite the emphasis on glycemic control, evidence of improvement in A1c control over time remains scant. In a recent study comparing nationally representative data from 1999–2002 with comparable data from 1988–1994, the mean A1c level declined from 7.8% to 7.7% (not significant at the 5% level) among adults with self-reported diabetes (6). The study found some evidence suggesting an improvement in poorly controlled A1c; the percentage of patients with A1c over 9.0% decreased from 24.5% to 20.6%, but this decline was not significant at the 5% level. Other studies have also shown little or no time trend in A1c levels (7,8); one (8) reported that the rate of glycemic control (A1c
