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13% of U.S. Adults Have Diabetes, But Many are Undiagnosed


In the United States, nearly 13 percent of adults age 20 and older
have diabetes, but 40 percent of them have not been diagnosed,
according to epidemiologists from the National Institutes of Health
(NIH) and the Centers for Disease Control and Prevention (CDC),
whose study includes newly available data from an Oral Glucose
Tolerance Test (OGTT). Diabetes is especially common in the elderly:
nearly one-third of those age 65 and older have the disease. An
additional 30 percent of adults have pre-diabetes, a condition
marked by elevated blood sugar that is not yet in the diabetic
range. The researchers report these findings in the February 2009
issue of Diabetes Care, which posted a pre-print version of the
article online at

The study compared the results of two national surveys that included
a fasting blood glucose (FBG) test and 2-hour glucose reading from
an OGTT. The OGTT gives more information about blood glucose abnormalities
than the FBG test, which measures blood glucose after an overnight
fast. The FBG test is easier and less costly than the OGTT, but
the 2-hour test is more sensitive in identifying diabetes and pre-diabetes,
especially in older people. Two-hour glucose readings that are
high but not yet diabetic indicate a greater risk of cardiovascular
disease and of developing diabetes than a high, but not yet diabetic,
fasting glucose level.

“We’re facing a diabetes epidemic that shows no signs of abating,
judging from the number of individuals with pre-diabetes,” said
lead author Catherine Cowie, Ph.D., of the National Institute of
Diabetes and Digestive and Kidney Diseases (NIDDK), a part of the
NIH. “For years, diabetes prevalence estimates have been based
mainly on data that included a fasting glucose test but not an
OGTT. The 2005-2006 National Health and Nutrition Examination Survey,
or NHANES, is the first national survey in 15 years to include
the OGTT. The addition of the OGTT gives us greater confidence
that we’re seeing the true burden of diabetes and pre-diabetes
in a representative sample of the U.S. population.”

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 leading cause of heart disease
and stroke. Type 2 diabetes accounts for up to 95 percent of all
diabetes cases and virtually all cases of undiagnosed diabetes.
Pre-diabetes, which causes no symptoms, substantially raises the
risk of a heart attack or stroke and of developing type 2 diabetes.

In its analysis, the team also found that:

  • The rate of diagnosed diabetes increased between the surveys,
    but the prevalence of undiagnosed diabetes and pre-diabetes remained
    relatively stable.
  • Minority groups continue to bear a disproportionate burden.
    The prevalence of diabetes, both diagnosed and undiagnosed, in
    non-Hispanic blacks and Mexican- Americans is about 70 to 80
    percent higher than that of non-Hispanic whites.
  • Diabetes prevalence was virtually the same in men and women,
    as was the proportion of undiagnosed cases.
  • Pre-diabetes is more common in men than in women (36 percent
    compared to 23 percent).
  • Diabetes is rare in youth ages 12 to 19 years, but about 16
    percent have pre-diabetes.

“These findings have grave implications for our health care system,
which is already struggling to provide care for millions of diabetes
patients, many of whom belong to vulnerable groups, such as the
elderly or minorities,” said Griffin P. Rodgers, M.D., director
of the NIDDK. “Of paramount importance is the need to curb the
obesity epidemic, which is the main factor driving the rise in
type 2 diabetes.”

The study is based on 2005-2006 data from the NHANES conducted
by the CDC’s National Center for Health Statistics. The survey
involved 7,267 people, who represented a national sample of persons
age 12 years and older. Participants were interviewed in their
homes and received a physical exam. A subsample had a blood sugar
reading taken after an overnight fast as well as the OGTT, sometimes
called a 2-hour glucose challenge. The OGTT measures blood glucose
2 hours after a person drinks a premeasured sugary beverage.
The findings were then compared to those of the last NHANES survey
that included the OGTT, which was conducted from 1988 to 1994.

“These findings of yet another increase in diabetes prevalence
are a reminder that a full-scale public health response is in order.
Re-directing the trends in diabetes will require changing the nutritional
and physical activity habits of people at risk, and also creative
and substantial efforts by health systems and communities," said
Ed Gregg, Ph.D., epidemiology and statistics branch chief in CDC’s
Division of Diabetes Translation.

“It’s important to know if you have diabetes or pre-diabetes,
because there’s so much you can do to preserve your health,” said
Joanne Gallivan, M.S., R.D., director of the National Diabetes
Education Program (NDEP) for the NIH. “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
a modest amount of weight and increasing physical activity will
greatly lower your risk of getting type 2 diabetes. If you already
have diabetes, controlling your blood glucose, blood pressure,
and cholesterol will prevent or delay the complications of diabetes.”

over age 45 should be tested for pre-diabetes or diabetes. Those
younger than 45 who are overweight and have another risk factor
should ask their health care provider about testing. People are
at greater risk of developing pre-diabetes and type 2 diabetes
if they:

  • are age 45 or older
  • have a family history of diabetes
  • are overweight
  • are inactive (exercise less than three times a week)
  • 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 or
  • have a history of disease of the blood vessels to the heart,
    brain, or legs
  • have had higher-than-normal blood glucose levels on previous

The National Diabetes Education Program, jointly sponsored by
the NIH, CDC, and 200 partner organizations, provides diabetes
education to improve the treatment and outcomes for people with
diabetes, promote early diagnosis, and prevent or delay the onset
of diabetes. In its “Small Steps. Big Rewards. Prevent Type 2 Diabetes” campaign,
the NDEP ( informs people at risk for type 2
diabetes that they have the power to turn the tide against this
disease. The “Control Your Diabetes for Life” campaign encourages
people with diabetes to control their blood glucose as well as
their blood pressure and cholesterol to prevent or delay complications,
which affect the heart, eyes, nerves, kidneys, and blood vessels.

CDC, through its Division of Diabetes Translation,
funds 59 diabetes prevention and control programs across all states,
and U.S.-Affiliated territories and island jurisdictions, and 11
tribes and tribal organizations.

NIDDK, part of the NIH, conducts and supports basic and clinical
research and research training on some of the most common, severe
and disabling conditions affecting Americans. The Institute's research
interests include: diabetes and other endocrine and metabolic diseases;
digestive diseases, nutrition, and obesity; and kidney, urologic
and hematologic diseases. For more information, visit

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, visit



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