Trends in prevalence and control of diabetes in the United States, 1988-1994 and 1999-2010

Abstract

Background: Trends in the prevalence and control of diabetes defined by hemoglobin A1c (HbA1c) levels are important for health care policy and planning.

Objective: To update trends in the prevalence of diabetes, prediabetes, and glycemic control.

Design: Cross-sectional.

Setting: NHANES (National Health and Nutrition Examination Survey) in 1988-1994 and 1999-2010.

Participants: Adults aged 20 years or older.

Measurements: We used calibrated HbA1c levels to define undiagnosed diabetes (≥6.5%); prediabetes (5.7% to 6.4%); and, among persons with diagnosed diabetes, glycemic control (<7.0% or <8.0%). Trends in HbA1c categories were compared with fasting glucose levels (≥7.0 mmol/L [≥126 mg/dL] and 5.6 to 6.9 mmol/L [100 to 125 mg/dL]).

Results: In 2010, approximately 21 million U.S. adults aged 20 years or older had total confirmed diabetes (self-reported diabetes or diagnostic levels for both fasting glucose and calibrated HbA1c). During 2 decades, the prevalence of total confirmed diabetes increased, but the prevalence of undiagnosed diabetes remained fairly stable, reducing the proportion of total diabetes cases that are undiagnosed to 11% in 2005-2010. The prevalence of prediabetes was lower when defined by calibrated HbA1c levels than when defined by fasting glucose levels but has increased from 5.8% in 1988-1994 to 12.4% in 2005-2010 when defined by HbA1c levels. Glycemic control improved overall, but total diabetes prevalence was greater and diabetes was less controlled among non-Hispanic blacks and Mexican Americans compared with non-Hispanic whites.

Limitation: Cross-sectional design.

Conclusion: Over the past 2 decades, the prevalence of total diabetes has increased substantially. However, the proportion of undiagnosed diabetes cases decreased, suggesting improvements in screening and diagnosis. Among the growing number of persons with diagnosed diabetes, glycemic control improved but remains a challenge, particularly among non-Hispanic blacks and Mexican Americans.

Primary funding source: National Institutes of Health.

Figure 1. Trends in the prevalence of diagnosed diabetes and undiagnosed diabetes (calibrated hemoglobin A1c ≥6.5%) by age (Panel A) and race/ethnic group (Panel B), U.S. adults aged 20 years or older, NHANES 1988-1994, 1999-2004, and 2005-2010

Legend: Abbreviations: White, Non-Hispanic White; Mex Am, Mexican-American; Black, Non-Hispanic Black

Figure 1. Trends in the prevalence of diagnosed diabetes and undiagnosed diabetes (calibrated hemoglobin A1c ≥6.5%) by age (Panel A) and race/ethnic group (Panel B), U.S. adults aged 20 years or older, NHANES 1988-1994, 1999-2004, and 2005-2010

Legend: Abbreviations: White, Non-Hispanic White; Mex Am, Mexican-American; Black, Non-Hispanic Black

Figure 2. Prevalence of total confirmed diabetes* and obesity†, U.S. adults aged 20 years or older, NHANES 1988-1994, 1999-2004, and 2005-2010

Legend: * “Total confirmed diabetes” was defined as diagnosed diabetes or undiagnosed diabetes with diagnostic levels of both HbA1c (≥6.5%) and fasting glucose (≥126 mg/dL). †Obesity defined as body mass index≥30 kg/m²; there were 601 people missing body mass index. Prevalence estimates for total confirmed diabetes and obesity were obtained using only the subsample of participants who attended the morning fasting session (N=7,385 for 1988-94; 5,680 for 1999-2004; 6,719 for 2005-10). The midpoint for obesity prevalence between 1988-94 and 1999-2004 was calculated as the average of the prevalence of the two time periods.