Diabetes Type 1 & 2
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Almost everyone knows someone who has diabetes. An estimated 18.2 million
people in the United States--6.3 percent of the population--have diabetes,
a serious, lifelong condition. Of those, 13 million have been diagnosed,
and about 5.2 million people have not yet been diagnosed. Each year, about
1.3 million people aged 20 or older are diagnosed with diabetes.
Diabetes is a disorder of metabolism--the way our bodies use digested
food for growth and energy. Most of the food we eat is broken down into
glucose, the form of sugar in the blood. Glucose is the main source of
fuel for the body.
After digestion, glucose passes into the bloodstream, where it is used
by cells for growth and energy. For glucose to get into cells, insulin
must be present. Insulin is a hormone produced by the pancreas, a large
gland behind the stomach.
When we eat, the pancreas automatically produces the right amount of insulin
to move glucose from blood into our cells. In people with diabetes, however,
the pancreas either produces little or no insulin, or the cells do not
respond appropriately to the insulin that is produced. Glucose builds up
in the blood, overflows into the urine, and passes out of the body. Thus,
the body loses its main source of fuel even though the blood contains large
amounts of glucose.
The three main types of diabetes are
- type 1 diabetes
- type 2 diabetes
- gestational diabetes
Type 1 diabetes is an autoimmune disease. An autoimmune disease results
when the body's system for fighting infection (the immune system) turns
against a part of the body. In diabetes, the immune system attacks the
insulin-producing beta cells in the pancreas and destroys them. The pancreas
then produces little or no insulin. A person who has type 1 diabetes must
take insulin daily to live.
At present, scientists do not know exactly what causes the body's immune
system to attack the beta cells, but they believe that autoimmune, genetic,
and environmental factors, possibly viruses, are involved. Type 1 diabetes
accounts for about 5 to 10 percent of diagnosed diabetes in the United
States. It develops most often in children and young adults, but can appear
at any age.
Symptoms of type 1 diabetes usually develop over a short period, although
beta cell destruction can begin years earlier. Symptoms include increased
thirst and urination, constant hunger, weight loss, blurred vision, and
extreme fatigue. If not diagnosed and treated with insulin, a person with
type 1 diabetes can lapse into a life-threatening diabetic coma, also known
as diabetic ketoacidosis.
The most common form of diabetes is type 2 diabetes. About 90 to 95 percent
of people with diabetes have type 2. This form of diabetes is associated
with older age, obesity, family history of diabetes, previous history of
gestational diabetes, physical inactivity, and ethnicity. About 80 percent
of people with type 2 diabetes are overweight.
Type 2 diabetes is increasingly being diagnosed in children and adolescents.
However, nationally representative data on prevalence of type 2 diabetes
in youth are not available.
When type 2 diabetes is diagnosed, the pancreas is usually producing enough
insulin, but for unknown reasons, the body cannot use the insulin effectively,
a condition called insulin resistance. After several years, insulin production
decreases. The result is the same as for type 1 diabetes--glucose builds
up in the blood and the body cannot make efficient use of its main source
of fuel.
The symptoms of type 2 diabetes develop gradually. Their onset is not
as sudden as in type 1 diabetes. Symptoms may include fatigue or nausea,
frequent urination, unusual thirst, weight loss, blurred vision, frequent
infections, and slow healing of wounds or sores. Some people have no symptoms.
Gestational diabetes develops only during pregnancy. Like type 2 diabetes,
it occurs more often in African Americans, American Indians, Hispanic Americans,
and among women with a family history of diabetes. Women who have had gestational
diabetes have a 20 to 50 percent chance of developing type 2 diabetes within
5 to 10 years.
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The fasting plasma glucose test is the preferred test for diagnosing type
1 or type 2 diabetes. It is most reliable when done in the morning. However,
a diagnosis of diabetes can be made after positive results on any one of
three tests, with confirmation from a second positive test on a different
day:
- A random (taken any time of day) plasma glucose value of 200 mg/dL
or more, along with the presence of diabetes symptoms.
- A plasma glucose value of 126 mg/dL or more after a person has fasted
for 8 hours.
- An oral glucose tolerance test (OGTT) plasma glucose value of 200 mg/dL
or more in a blood sample taken 2 hours after a person has consumed a
drink containing 75 grams of glucose dissolved in water. This test, taken
in a laboratory or the doctor's office, measures plasma glucose at timed
intervals over a 3-hour period.
Gestational diabetes is diagnosed based on plasma glucose values measured
during the OGTT. Glucose levels are normally lower during pregnancy, so
the threshold values for diagnosis of diabetes in pregnancy are lower.
If a woman has two plasma glucose values meeting or exceeding any of the
following numbers, she has gestational diabetes: a fasting plasma glucose
level of 95 mg/dL, a 1-hour level of 180 mg/dL, a 2-hour level of 155 mg/dL,
or a 3-hour level of 140 mg/dL.
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People with pre-diabetes, a state between "normal" and "diabetes," are
at risk for developing diabetes, heart attacks, and strokes. However, studies
suggest that weight loss and increased physical activity can prevent or
delay diabetes. There are two forms of pre-diabetes.
Impaired Fasting GlucoseA person has impaired fasting glucose (IFG) when
fasting plasma glucose is 100 to 125 mg/dL. This level is higher than normal
but less than the level indicating a diagnosis of diabetes. Impaired Glucose
Tolerance
Impaired glucose tolerance (IGT) means that blood glucose during the oral
glucose tolerance test is higher than normal but not high enough for a
diagnosis of diabetes. IGT is diagnosed when the glucose level is 140 to
199 mg/dL 2 hours after a person drinks a liquid containing 75 grams of
glucose.
About 35 million people ages 40 to 74 have impaired fasting glucose and
16 million have impaired glucose tolerance. Because some people have both
conditions, the total number of U.S. adults ages 40 to 74 with pre-diabetes
comes to about 41 million. These recent estimates were calculated using
data from the 1988-1994 National Health and Nutrition Examination Survey
and projected to the 2000 U.S. population.
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Diabetes is widely recognized as one of the leading causes of death and
disability in the United States. In 2000, it was the sixth leading cause
of death. However, diabetes is likely to be underreported as the underlying
cause of death on death certificates. About 65 percent of deaths among
those with diabetes are attributed to heart disease and stroke.
Diabetes is associated with long-term complications that affect almost
every part of the body. The disease often leads to blindness, heart and
blood vessel disease, stroke, kidney failure, amputations, and nerve damage.
Uncontrolled diabetes can complicate pregnancy, and birth defects are more
common in babies born to women with diabetes.
In 2002, diabetes cost the United States $132 billion. Indirect costs,
including disability payments, time lost from work, and premature death,
totaled $40 billion; direct medical costs for diabetes care, including
hospitalizations, medical care, and treatment supplies, totaled $92 billion.
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Diabetes is not contagious. People cannot "catch" it from each other.
However, certain factors can increase the risk of developing diabetes.
Type 1 diabetes occurs equally among males and females, but is more common
in whites than in nonwhites. Data from the World Health Organization's
Multinational Project for Childhood Diabetes indicate that type 1 diabetes
is rare in most African, American Indian, and Asian populations. However,
some northern European countries, including Finland and Sweden, have high
rates of type 1 diabetes. The reasons for these differences are unknown.
Type 2 diabetes is more common in older people, especially in people who
are overweight, and occurs more often in African Americans, American Indians,
some Asian Americans, Native Hawaiians and other Pacific Islander Americans,
and Hispanic Americans. On average, non-Hispanic African Americans are
1.6 times as likely to have diabetes as non-Hispanic whites of the same
age. Hispanic Americans are 1.5 times as likely to have diabetes as non-Hispanic
whites of similar age. American Indians have one of the highest rates of
diabetes in the world. On average, American Indians and Alaska Natives
are 2.3 times as likely to have diabetes as non-Hispanic whites of similar
age. Although prevalence data for diabetes among Asian Americans and Pacific
Islanders are limited, some groups, such as Native Hawaiians and Japanese
and Filipino residents of Hawaii aged 20 or older, are about twice as likely
to have diabetes as white residents of Hawaii of similar age.
The prevalence of diabetes in the United States is likely to increase
for several reasons. First, a large segment of the population is aging.
Also, Hispanic Americans and other minority groups make up the fastest-growing
segment of the U.S. population. Finally, Americans are increasingly overweight
and sedentary. According to recent estimates, the prevalence of diabetes
in the United States is predicted to reach 8.9 percent of the population
by 2025.
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Before the discovery of insulin in 1921, everyone with type 1 diabetes
died within a few years after diagnosis. Although insulin is not considered
a cure, its discovery was the first major breakthrough in diabetes treatment.
Today, healthy eating, physical activity, and taking insulin via injection
or an insulin pump are the basic therapies for type 1 diabetes. The amount
of insulin must be balanced with food intake and daily activities. Blood
glucose levels must be closely monitored through frequent blood glucose
checking.
Healthy eating, physical activity, and blood glucose testing are the basic
management tools for type 2 diabetes. In addition, many people with type
2 diabetes require oral medication, insulin, or both to control their blood
glucose levels.
People with diabetes must take responsibility for their day-to-day care.
Much of the daily care involves keeping blood glucose levels from going
too low or too high. When blood glucose levels drop too low--a condition
known as hypoglycemia--a person can become nervous, shaky, and confused.
Judgment can be impaired, and if blood glucose falls too low, fainting
can occur.
A person can also become ill if blood glucose levels rise too high, a
condition known as hyperglycemia.
People with diabetes should see a health care provider who will help them
learn to manage their diabetes and who will monitor their diabetes control.
An endocrinologist is a doctor who often specializes in diabetes care.
In addition, people with diabetes often see ophthalmologists for eye examinations,
podiatrists for routine foot care, and dietitians and diabetes educators
to learn the skills needed for day-to-day diabetes management.
The goal of diabetes management is to keep blood glucose levels as close
to the normal range as safely possible. A major study, the Diabetes Control
and Complications Trial (DCCT), sponsored by the National Institute of
Diabetes and Digestive and Kidney Diseases (NIDDK), showed that keeping
blood glucose levels close to normal reduces the risk of developing major
complications of type 1 diabetes.
This 10-year study, completed in 1993, included 1,441 people with type
1 diabetes. The study compared the effect of two treatment approaches--intensive
management and standard management--on the development and progression
of eye, kidney, and nerve complications of diabetes. Intensive treatment
aimed to keep hemoglobin A1C as close to normal (6 percent) as possible.
Hemoglobin A1C reflects average blood glucose over a 2- to 3-month period.
Researchers found that study participants who maintained lower levels of
blood glucose through intensive management had significantly lower rates
of these complications. More recently, a followup study of DCCT participants
showed that the ability of intensive control to lower the complications
of diabetes has persisted 8 years after the trial ended.
The United Kingdom Prospective Diabetes Study, a European study completed
in 1998, showed that intensive control of blood glucose and blood pressure
reduced the risk of blindness, kidney disease, stroke, and heart attack
in people with type 2 diabetes.
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In recent years, advances in diabetes research have led to better ways
of managing diabetes and treating its complications. Major advances include
- development of quick-acting and long-acting insulins
- better ways to monitor blood glucose and for people with diabetes to
check their own blood glucose levels, including advances in noninvasive
blood glucose monitoring
- development of external insulin pumps that deliver insulin, replacing
daily injections
- laser treatment for diabetic eye disease, reducing the risk of blindness
- successful transplantation of both kidneys and pancreas in people whose
kidneys fail because of diabetes
- better ways of managing diabetes in pregnant women, improving their
chances of a successful outcome
- new drugs to treat type 2 diabetes and better ways to manage this form
of diabetes through weight control
- evidence that intensive management of blood glucose reduces and may
prevent development of diabetes complications
- demonstration that two types of antihypertensive drugs, ACE (angiotensin-converting
enzyme) inhibitors and ARBs (angiotensin receptor blockers), are more
effective than other antihypertensive drugs in reducing a decline in
kidney function in people with diabetes
- promising results with islet transplantation for type 1 diabetes reported
by the University of Alberta in Canada
- evidence that people at high risk for type 2 diabetes can lower their
chances of developing the disease through diet, weight loss, and physical
activity
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Researchers continue to look for the cause or causes of diabetes and ways
to prevent and cure the disease. Scientists are searching for genes that
may be involved in type 1 or type 2 diabetes. Some genetic markers for
type 1 diabetes have been identified, and it is now possible to screen
relatives of people with type 1 diabetes to determine whether they are
at risk.
Type 1 Diabetes
The Diabetes Prevention Trial--Type 1 (DPT-1) identified relatives at
risk for developing type 1 diabetes and investigated two ways to delay
or prevent type 1 diabetes. Results showed that neither low-dose insulin
injections nor an oral form of insulin were successful in delaying or preventing
type 1 diabetes in people at risk.
The DPT-1 was funded by the NIDDK, the National Institute of Allergy and
Infectious Diseases, the National Institute of Child Health and Human Development,
and the National Center for Research Resources within the National Institutes
of Health, as well as the American Diabetes Association and the Juvenile
Diabetes Research Foundation International.
Researchers are working on a way for people with type 1 diabetes to live
without daily insulin injections. In an experimental procedure called islet
transplantation, islets are taken from a donor pancreas and transferred
into a person with type 1 diabetes. Once implanted, the beta cells in these
islets begin to make and release insulin.
Scientists have made many advances in islet transplantation in recent
years. Since reporting their findings in the June 2000 issue of the New
England Journal of Medicine, researchers at the University of Alberta
in Edmonton, Alberta, Canada, have continued to use a procedure called
the Edmonton protocol to transplant pancreatic islets into people with
type 1 diabetes. A multicenter clinical trial of the Edmonton protocol
for islet transplantation is currently under way, and results will be announced
in several years. According to the International Islet Transplant Registry,
as of June 2003 about 50 percent of the patients have remained free of
the need for insulin injections up to 1 year after receiving a transplant.
A clinical trial of the Edmonton protocol is also being conducted by the
Immune Tolerance Network, funded by the National Institutes of Health and
the Juvenile Diabetes Research Foundation International.
The goal of islet transplantation is to infuse enough islets to control
the blood glucose level without insulin injections. For an average-sized
person (70 kg), a typical transplant requires about 1 million islets, extracted
from two donor pancreases. Because good control of blood glucose can slow
or prevent the progression of complications associated with diabetes, such
as nerve or eye damage, a successful transplant may reduce the risk of
these complications. But a transplant recipient will need to take immunosuppressive
drugs to stop the immune system from rejecting the transplanted islets.
Researchers are trying to find new approaches that will allow successful
transplantation without the use of immunosuppressive drugs. These drugs
have significant side effects and their long-term effects are still unknown.
Immediate side effects of immunosuppressive drugs may include mouth sores
and gastrointestinal problems, such as stomach upset or diarrhea. Patients
may also have increased blood cholesterol levels, decreased white blood
cell counts, decreased kidney function, and increased susceptibility to
bacterial and viral infections. Taking immunosuppressive drugs increases
the risk of tumors and cancer as well.
Researchers do not fully know what long-term effects islet transplantation
may have. Although the early results of the Edmonton protocol are very
encouraging, more research is needed to answer questions about how long
the islets will survive and how often the transplantation procedure will
be successful.
A major obstacle to widespread use of islet transplantation will be the
shortage of islet cells. The supply available from deceased donors will
be enough for only a small percentage of those with type 1 diabetes. However,
researchers are pursuing alternative sources, such as creating islet cells
from other types of cells. New technologies could then be employed to grow
islet cells in the laboratory.
In 1996, NIDDK launched its Diabetes Prevention Program (DPP). The goal
of this research effort was to learn how to prevent or delay type 2 diabetes
in people with impaired glucose tolerance (IGT), a strong risk factor for
type 2 diabetes.
The findings of the DPP, which were released in August 2001, showed that
people at high risk for type 2 diabetes could sharply lower their chances
of developing the disease through diet and exercise. In addition, treatment
with the oral diabetes drug metformin also reduced diabetes risk, though
less dramatically.
Participants randomly assigned to intensive lifestyle intervention reduced
their risk of getting type 2 diabetes by 58 percent. On average, this group
maintained their physical activity at 30 minutes per day, usually with
walking or other moderate intensity exercise, and lost 5 to 7 percent of
their body weight. Participants randomized to treatment with metformin
reduced their risk of getting type 2 diabetes by 31 percent.
Of the 3,234 participants enrolled in the DPP, 45 percent were from minority
groups that suffer disproportionately from type 2 diabetes: African Americans,
Hispanic Americans, Asian Americans and Pacific Islanders, and American
Indians. The trial also recruited other groups known to be at higher risk
for type 2 diabetes, including individuals aged 60 and older, women with
a history of gestational diabetes, and people with a first-degree relative
with type 2 diabetes.
The National Institutes of Health (NIH) is studying the best strategies
to prevent and treat cardiovascular disease (CVD) in people with diabetes
in three trials: Look AHEAD, ACCORD, and BARI 2D. These studies are all
joint efforts of the NIDDK and the National Heart, Lung, and Blood Institute.
The Look AHEAD: Action for Health in Diabetes study will be the largest
clinical trial to date to examine the long-term health effects of voluntary
weight loss. This multi-center, randomized clinical trial will study the
consequences of a lifestyle intervention designed to achieve and maintain
weight loss over the long term through decreased caloric intake and increased
exercise. Look AHEAD will focus on the disease most associated with overweight
and obesity, type 2 diabetes, and on the outcome that causes the greatest
morbidity and mortality in people with type 2 diabetes, cardiovascular
disease.
The Action to Control Cardiovascular Risk in Diabetes (ACCORD) study,
a randomized multi-center trial, is being undertaken by the NIH to study
three key approaches to preventing major cardiovascular events in individuals
with type 2 diabetes. The primary outcome to be measured is the first occurrence
of a major cardiovascular disease event, specifically heart attack, stroke,
or cardiovascular death. In addition, the study will investigate the impact
of the treatment strategies on other cardiovascular outcomes; total mortality;
limb amputation; eye, kidney, or nerve disease; health-related quality
of life; and cost-effectiveness.
The Bypass Angioplasty Revascularization Investigation in Type 2 Diabetics
(BARI 2D) trial, a 5-year, multi-center clinical trial, will compare medical
versus early surgical management of patients with type 2 diabetes who also
have coronary artery disease and stable angina or ischemia. At the same
time, BARI 2D will study the effect of two different strategies to control
blood glucose--providing insulin versus increasing the sensitivity of the
body to insulin--on the risk of cardiovascular mortality and morbidity.
Several new drugs have been developed to treat type 2 diabetes. By using
the oral diabetes medications now available, many people can control blood
glucose levels without insulin injections. Studies are under way to determine
how best to use these drugs to manage type 2 diabetes.
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- a disorder of metabolism--the way the body digests food for energy
and growth
What are the main types of diabetes?
- type 1 diabetes
- type 2 diabetes
- gestational diabetes
What are the impacts of diabetes?
- It affects 18.2 million people--6.3 percent of the U.S. population.
- It is a leading cause of death and disability.
- It costs $132 billion per year.
Who gets diabetes?
- people of any age
- people with a family history of diabetes
- others with high risk: commonly older people, overweight and sedentary
people, African Americans, Alaska Natives, American Indians, Asian Americans,
Native Hawaiians, some Pacific Islander Americans, and Hispanic Americans
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To learn more about type 1, type 2, and gestational diabetes, as well
as diabetes research, statistics, and education, contact
National Diabetes Education
Program
American Diabetes Association
Juvenile Diabetes Research
Foundation International
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