One-Third of Adults with Diabetes Still Donít
Know They Have It
The prevalence of diagnosed diabetes in U.S. adults age 20 and
older has risen from about 5.1 percent to 6.5 percent, according
to researchers at the National Institutes of Health (NIH) and the
Centers for Disease Control and Prevention (CDC), who analyzed national
survey data from two periods — 1988 to 1994 and 1999 to 2002.
However, the percentage of adults with undiagnosed diabetes did
not change significantly over the years studied. About 2.8 percent
of U.S. adults — one-third of those with diabetes —
still don’t know they have it.
The study, published in the June 2006 issue of Diabetes Care,
notes that type 2 diabetes accounts for up to 95 percent of all
diabetes cases and virtually all undiagnosed diabetes cases. Diabetes
is a group of diseases marked by high levels of blood glucose resulting
from defects in insulin production, insulin action, or both. It
is the most common cause of blindness, kidney failure, and amputations
in adults and a major cause of heart disease and stroke.
Over the years studied, about 26 percent of adults age 20 and older
continued to have impaired fasting glucose (IFG), a form of pre-diabetes.
IFG, in which blood glucose measured after an overnight fast is
high but not yet diagnostic of diabetes, increases the risk of heart
disease as well as the risk of developing type 2 diabetes.
“It’s important to know if you have pre-diabetes or
undiagnosed type 2 diabetes,” said Dr. Larry Blonde, chair
of the National Diabetes Education Program (NDEP), jointly sponsored
by the NIH, CDC, and 200 partner organizations. “You should
talk to your health care professional about your risk. If your blood
glucose is high but not high enough to be diagnosed as diabetes,
losing weight and increasing physical activity will greatly lower
your risk of getting type 2 diabetes. If you have diabetes, controlling
your blood glucose, blood pressure, and cholesterol will prevent
or delay the complications of diabetes.”
The researchers also found that:
- nearly 22 percent of people age 65 and older had diabetes.
- about 13 percent of non-Hispanic blacks age 20 and older had
diabetes. Diabetes was twice as common in non-Hispanic blacks
compared to non-Hispanic whites.
- about 8 percent of Mexican Americans age 20 and older had diabetes.
Because the average age of Mexican Americans is younger than for
other groups, the age-and sex-adjusted prevalence of diabetes
in Mexican Americans is twice that of non-Hispanic whites and
about equal to that of non-Hispanic blacks.
- IFG and undiagnosed diabetes were about 70 percent more common
in men than in women, especially in non-Hispanic white men.
- nearly 40 percent of people age 65 and older had IFG, which
becomes more common with age.
In the study, the researchers compared two slices of data, one
from 1988 to 1994 and the other from 1999 to 2002. The data were
derived from a national sample of U.S. adults age 20 years and older
who took part in the National Health and Nutrition Examination Survey
(NHANES) conducted by the CDC’s National Center for Health
Statistics. Survey participants were interviewed in their homes
and received a physical exam with a blood test, which included a
glucose reading taken after an overnight fast. The NHANES is unique
because it includes a blood test that detects undiagnosed diabetes
“This study updates and generally corroborates earlier analyses
that were based on 2 years of NHANES data,” said lead author
Catherine Cowie, Ph.D., of the National Institute of Diabetes and
Digestive and Kidney Diseases (NIDDK). “We’re seeing
a rising prevalence of diagnosed diabetes that is not substantially
offset by a drop in the rate of undiagnosed — about one-third
of adults with diabetes still don’t know they have it. Another
26 percent of adults have a form of pre-diabetes.”
Pre-diabetes, which usually causes no symptoms, is serious because
many people with the condition develop type 2 diabetes in the next
10 years. Also, pre-diabetes substantially raises the risk of a
heart attack or stroke even if type 2 diabetes does not develop.
People with pre-diabetes may have IFG or impaired glucose tolerance
(IGT) or both.
- In IFG, blood glucose is high (100 to 125 milligrams per deciliter
or mg/dL) after an overnight fast but not high enough to be diagnostic
- In IGT, blood glucose is high (140 to 199 mg/dL) 2 hours after
drinking a sugary drink in an oral glucose tolerance test but
not high enough to be diagnostic of diabetes.
In the current study, researchers did not assess the prevalence
of IGT because an oral glucose tolerance test was not a part of
People with pre-diabetes can often prevent or delay diabetes if
they lose a modest amount of weight by cutting calories in their
diet and increasing physical activity (for example, walking 30 minutes
a day 5 days a week). A major study of people with IGT has shown
that lifestyle changes leading to a 5 to 7 percent weight loss lowered
diabetes onset by 58 percent.
If you are over age 45, you should consult your health care provider
about testing for pre-diabetes or diabetes. If you are younger than
45, overweight, and have another risk factor, you should ask about
testing. You are at greater risk of developing pre-diabetes and
type 2 diabetes if you:
- are age 45 or older
- have a family history of diabetes
- are overweight
- have an inactive lifestyle (exercise less than three times a
- are members of a high-risk ethnic population (e.g., African
American, Hispanic/Latino American, American Indian and Alaska
Native, Asian American, Pacific Islander)
- have high blood pressure: 140/90 mm/Hg or higher
- have an HDL cholesterol less than 35 mg/dL or a triglyceride
level 250 mg/dL or higher
- have had diabetes that developed during pregnancy (gestational
diabetes) or have given birth to a baby weighing more than 9 pounds
- have polycystic ovary syndrome, a metabolic disorder that affects
the female reproductive system
- have acanthosis nigricans (dark, thickened skin around neck
- have a history of disease of the blood vessels to the heart,
brain, or legs
- have had IFG or IGT on previous testing.
In its “Small Steps. Big Rewards. Prevent Type 2 Diabetes”
campaign, the NDEP (www.ndep.nih.gov/)
is reaching out to people at risk for type 2 diabetes with the message
that they have the power to turn the tide against this disease.
The NDEP campaign, “Control Your Diabetes for Life,”
encourages people with diabetes to control their blood glucose as
well as their blood pressure and cholesterol. By keeping all three
as close to normal as possible, people with diabetes can prevent
or delay the development and progression of diabetes complications,
which affect the heart, eyes, nerves, kidneys, and blood vessels.
For more diabetes statistics, see http://diabetes.niddk.nih.gov/dm/pubs/statistics/index.htm.
The National Institute of Diabetes and Digestive and Kidney Diseases,
part of the NIH, conducts and supports research on diabetes; endocrine
and metabolic diseases; digestive diseases, nutrition, and obesity;
and kidney, urologic and hematologic diseases. Spanning the full
spectrum of medicine and afflicting people of all ages and ethnic
groups, these diseases encompass some of the most common, severe,
and disabling conditions affecting Americans.
The NIH and the CDC, agencies of the U.S. Department of Health
and Human Services, sponsor the National Diabetes Education Program,
which is working to reduce the morbidity and mortality associated
with diabetes. For information about CDC and its programs, see www.cdc.gov.
The National Institutes of Health (NIH) — The Nation's
Medical Research Agency — includes 27 Institutes and
Centers and is a component of the U.S. Department of Health and
Human Services. It is the primary federal agency for conducting
and supporting basic, clinical and translational medical research,
and it investigates the causes, treatments, and cures for both common
and rare diseases. For more information about NIH and its programs,