Fact Sheet N° 138
Revised April 2002
Diabetes mellitus is a chronic disease
caused by inherited and/or acquired deficiency in production of
insulin by the pancreas, or by the ineffectiveness of the insulin
produced. Such a deficiency results in increased concentrations of
glucose in the blood, which in turn damage many of the body's systems,
in particular the blood vessels and nerves.
There are two principle
forms of diabetes:
Type 2 diabetes (formerly named
non-insulin-dependent) which results from the body's inability to
respond properly to the action of insulin produced by the
pancreas. Type 2 diabetes is much more common and accounts for
around 90% of all diabetes cases worldwide. It occurs most
frequently in adults, but is being noted increasingly in
adolescents as well.
Certain genetic markers
have been shown to increase the risk of developing Type 1 diabetes.
Type 2 diabetes is strongly familial, but it is only recently that
some genes have been consistently associated with increased risk for
Type 2 diabetes in certain populations. Both types of diabetes are
complex diseases caused by mutations in more than one gene, as well as
by environmental factors.
Diabetes in pregnancy
may give rise to several adverse outcomes, including congenital
malformations, increased birth weight and an elevated risk of
perinatal mortality. Strict metabolic control may reduce these risks
to the level of those of non-diabetic expectant mothers.
tolerance (IGT) and impaired fasting glycaemia (IFG) refer to levels
of blood glucose concentration above the normal range, but below those
which are diagnostic for diabetes. Subjects with IGT and/or IFG are at
substantially higher risk of developing diabetes and cardiovascular
disease than those with normal glucose tolerance. The benefits of
clinical intervention in subjects with moderate glucose intolerance is
a topic of much current interest.
Symptoms: The symptoms
of diabetes may be pronounced, subdued, or even absent.
In Type 1 diabetes, the classic
symptoms are excessive secretion of urine (polyuria), thirst (polydipsia),
weight loss and tiredness.
These symptoms may be less marked in
Type 2 diabetes. In this form, it can also happen that no early
symptoms appear and the disease is only diagnosed several years
after its onset, when complications are already present.
Recently compiled data show that
approximately 150 million people have diabetes mellitus worldwide,
and that this number may well double by the year 2025. Much of
this increase will occur in developing countries and will be due
to population growth, ageing, unhealthy diets, obesity and
By 2025, while most people with
diabetes in developed countries will be aged 65 years or more, in
developing countries most will be in the 45-64 year age bracket
and affected in their most productive years.
About 40% of diabetes sufferers
require oral agents for satisfactory blood glucose control, and
some 40% need insulin injections. This hormone was isolated by
Frederic Banting and Charles Best in 1921 in Canada. It
revolutionized the treatment of diabetes and prevention of its
complications, transforming Type 1 diabetes from a fatal disease
to one in which long-term survival became achievable.
People with Type 1 diabetes are
usually totally dependent on insulin injections for survival. Such
people require daily administration of insulin. The majority of
people suffering from diabetes have the Type 2 form. Although they
do not depend on insulin for survival, about one third of
sufferers needs insulin for reducing their blood glucose levels.
associated with Diabetes Mellitus:
Diabetic retinopathy is a leading
cause of blindness and visual disability. Diabetes mellitus is
associated with damage to the small blood vessels in the retina,
resulting in loss of vision. Findings, consistent from study to
study, make it possible to suggest that, after 15 years of
diabetes, approximately 2% of people become blind, while about 10%
develop severe visual handicap. Loss of vision due to certain
types of glaucoma and cataract may also be more common in people
with diabetes than in those without the disease.
control can delay the onset and progression of diabetic retinopathy.
Loss of vision and blindness in persons with diabetes can be
prevented by early detection and treatment of vision-threatening
retinopathy: regular eye examinations and timely intervention with
laser treatment, or through surgery in cases of advanced
retinopathy. There is evidence that, even in developed countries, a
large proportion of those in need is not receiving such care due to
lack of public and professional awareness, as well as an absence of
treatment facilities. In developing countries, in many of which
diabetes is now common, such care is inaccessible to the majority of
Diabetes is among the leading causes
of kidney failure, but its frequency varies between populations
and is also related to the severity and duration of the disease.
Several measures to slow down the progress of renal damage have
been identified. They include control of high blood glucose,
control of high blood pressure, intervention with medication in
the early stage of kidney damage, and restriction of dietary
protein. Screening and early detection of diabetic kidney disease
are an important means of prevention.
Heart disease accounts for
approximately 50% of all deaths among people with diabetes in
industrialized countries. Risk factors for heart disease in people
with diabetes include smoking, high blood pressure, high serum
cholesterol and obesity. Diabetes negates the protection from
heart disease which pre-menopausal women without diabetes
experience. Recognition and management of these conditions may
delay or prevent heart disease in people with diabetes.
Diabetic foot disease, due to
changes in blood vessels and nerves, often leads to ulceration and
subsequent limb amputation. It is one of the most costly
complications of diabetes, especially in communities with
inadequate footwear. It results from both vascular and
neurological disease processes. Diabetes is the most common cause
of non-traumatic amputation of the lower limb, which may be
prevented by regular inspection and good care of the foot.
population-based studies in China, Finland and USA have recently
demonstrated the feasibility of preventing, or delaying, the onset of
diabetes in overweight subjects with mild glucose intolerance (IGT).
The studies suggest that even moderate reduction in weight and only
half an hour of walking each day reduced the incidence of diabetes by
more than one half.
Diabetes is a serious
and costly disease which is becoming increasingly common, especially
in developing countries and disadvantaged minorities. However, there
are ways of preventing it and/or controlling its progress. Public and
professional awareness of the risk factors for, and symptoms of
diabetes are an important step towards its prevention and control.
information, please contact the Communications Office of the
Director-General's Office, WHO Geneva, Tel (+41 22) 791 2222, Fax (+41
22) 791 4858; e-mail: email@example.com.
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