2 tables omitted
Diabetes and its complications are major causes of morbidity and mortality
in the United States and contribute substantially to health-care costs. Data
from the National Health Interview Survey (NHIS) and the Behavioral Risk Factor
Surveillance System (BRFSS) have documented steady increases in the prevalence
of diabetes.1,2 However, these surveys rely only on self-reports
of previously diagnosed diabetes and cannot measure the prevalence of undiagnosed
diabetes. The change in prevalence demonstrated by these data might reflect
other factors such as enhanced detection rather than true increases. The National
Health and Nutrition Examination surveys (NHANES) are the only nationally
representative surveys that examine both diagnosed and undiagnosed diabetes.
During 1976-1980 (NHANES II) and 1988-1994 (NHANES III), the overall combined
prevalence of diabetes (diagnosed and undiagnosed on the basis of fasting
glucose) increased.3 This report presents data on prevalence of
diagnosed and undiagnosed diabetes and impaired fasting glucose from NHANES
1999-2000 and NHANES III (1988-1994). The findings indicate that diabetes
and impaired fasting glucose continue to affect a major proportion of the
U.S. population. An estimated 29 million (14.4%) persons aged ≥20 years
had either diagnosed diabetes, undiagnosed diabetes, or impaired fasting glucose;
29% of diabetes cases were undiagnosed. Persons can reduce their risk for
diabetes through weight management and physical activity.
NHANES 1999-20004 was designed to be nationally representative
of the U.S. civilian, noninstitutionalized population on the basis of a complex,
multistage probability sample. Survey participants were interviewed in their
homes and subprovide estimates that were representative of the U.S. population.
Prevalence based on fasting glucose in the morning sample of persons without
diagnosed diabetes was adjusted as described previously6 so estimates
based on these data would represent the total U.S. population. Age- and sex-adjusted
rates were computed by the direct method by using U.S. 2000 Census data, with
age categories of 20-39, 40-59, and ≥60 years. Replicated variance estimation
methods were used to calculate the standard errors, accounting for both the
complex sample design and the use of both interview and morning examination
sample data in combination. Two sample t-tests were used to test differences
The estimated unadjusted prevalence of previously diagnosed diabetes
in adults aged ≥20 years during 1999-2000 was 5.9% (95% confidence interval
[CI] = 4.9-6.9), representing 11.8 million (95% CI = 9.8-13.8 million) U.S.
adults. The prevalence increased by age, reaching 15.0% (95% CI = 12.6-17.5)
among persons aged ≥60 years. Rates were similar by sex. The adjusted prevalence
was significantly lower in non-Hispanic whites compared with Mexican Americans
and non-Hispanic blacks. The unadjusted prevalence of undiagnosed diabetes
based on fasting glucose in adults aged ≥20 years was 2.4% (95% CI = 1.5-3.4)
during 1999-2000, representing 4.9 million (95% CI = 3.0-6.8 million) U.S.
adults. Prevalence increased slightly with age and was similar in men and
women. Rates were similar by race/ethnicity.
Combining diagnosed and undiagnosed diabetes, the unadjusted prevalence
of total diabetes during 1999-2000 was 8.3% (95% CI = 6.9-9.8), affecting
an estimated 16.7 million (95% CI = 13.8-19.6 million) persons aged ≥20
years. Differences in prevalence by age, sex, and race/ethnicity mirrored
those for diagnosed diabetes. During 1999-2000, the proportion of total diabetes
that was undiagnosed was 29% (95% CI = 21%-38%). The overall prevalence of
diagnosed diabetes, undiagnosed diabetes, total diabetes, and the overall
proportion of total diabetes that was undiagnosed did not change significantly
from 1988-1994 to 1999-2000.
Overall prevalence of impaired fasting glucose during 1999-2000 was
6.1% (95% CI = 4.4-7.9), representing 12.3 million (95% CI = 8.8-15.8 million)
persons aged ≥20 years. Rates increased with age, were higher in men (7.9%)
(95% CI = 5.5-10.2) than in women (4.5%) (95% CI = 2.8-6.2), and were similar
by race/ethnicity. The overall decrease in prevalence observed from 1988-1994
to 1999-2000 was not statistically significant.
During 1999-2000, the combined unadjusted prevalence of total diabetes
and impaired fasting glucose in adults aged ≥20 years was 14.4% (95% CI
= 12.3%-16.5%), representing 29.0 million (95% CI = 24.8-33.2 million) persons.
Prevalence increased with age, reaching 33.6% (95% CI = 28.8%-38.4%) by age
≥60 years. Adjusted prevalence was significantly lower in women than in
men, and in non-Hispanic whites compared with non-Hispanic blacks and Mexican
Americans. Rates were similar in 1988-1994 and 1999-2000.
CC Cowie, PhD, National Institute of Diabetes and Digestive and Kidney
Diseases, Bethesda; KF Rust, PhD, Westat, Inc., Rockville; D Byrd-Holt, Social
& Scientific Systems, Inc., Silver Spring, Maryland. MS Eberhardt, PhD,
S Saydah, PhD, National Center for Health Statistics; LS Geiss, MA, MM Engelgau,
MD, ES Ford, MD, EW Gregg, PhD, National Center for Chronic Disease Prevention
and Health Promotion, CDC.
Diabetes continues to affect a substantial proportion of U.S. adults.
On the basis of NHANES 1999-2000, a total of 8.3% of persons aged ≥20 years
had either diagnosed or undiagnosed diabetes, and this percent increased to
19.2% for persons aged ≥60 years. Men and women were affected similarly
by diabetes. However, non-Hispanic blacks and Mexican Americans had a disproportionately
high prevalence compared with non-Hispanic whites. Impaired fasting glucose
increases the risk for diabetes and is associated with other cardiovascular
risk factors.7 In 1999-2000, an additional 6.1% of adults had impaired
fasting glucose (a rate similar in magnitude to the prevalence of diagnosed
diabetes), increasing to 14.4% for persons aged ≥60 years, with men affected
more than women. Overall, an estimated 14.4% of the U.S. population aged ≥20
years and 33.6% of those aged ≥60 years had either diabetes or impaired
The findings in this report are subject to at least two limitations.
First, the substantially smaller sample size of NHANES 1999-2000 limits the
precision of estimated prevalences and the statistical power to detect changes
in these estimates between the surveys. Second, because an oral glucose tolerance
test (OGTT) was not performed in NHANES 1999-2000, this survey does not capture
the additional proportion of persons with abnormal postload glucose tolerance
and normal fasting glucose levels. NHANES III (1988-1994) indicated that total
glucose intolerance was 36% higher based on OGTT data.3
The findings in this report indicate that the prevalence of diabetes,
either diagnosed or undiagnosed, and impaired fasting glucose did not appear
to increase substantially during the 1990s. Estimates of diagnosed diabetes
in NHANES 1999-2000 are similar in magnitude to those from NHIS and BRFSS
during the same years. The apparent lack of increase in prevalence is unexpected
in light of the increasing prevalence of obesity and overweight in U.S. adults
documented by the NHANES surveys.8 Although a potential change
in the ratio of undiagnosed to total diabetes prevalence would be an important
finding, the observed differences are not statistically significant. Further
investigation with additional years of NHANES data will be necessary to provide
more precise estimates. In addition, the potential impact on the prevalence
estimates of the change in diagnosis of diabetes adopted by the ADA in 19975 should be accounted for, along with changes in demographic characteristics
Recent trials have documented that lifestyle modification (i.e., weight
management and increased physical activity) reduces the risk for developing
diabetes among persons with impaired glucose tolerance.9 Other
clinical trials and studies have demonstrated that the risk for diabetic complications
is reduced substantially by blood glucose, blood pressure, and blood lipid
control.10 These messages should continue to be communicated through
education and outreach activities such as the "Steps to a Healthier US" by
the U.S. Department of Health and Human Services (http://www.healthierus.gov/steps), and the "Small Steps, Big Rewards" (http://ndep.nih.gov/get-info/dpc.htm
and "Control the ABCs of Diabetes" (http://ndep.nih.gov/control/control.htm) campaigns of the National Diabetes Education Program.
References: 10 available
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