The clinical course and outcome of
diabetes depends on the type.
Course of type
For more than 25 years, it has been proposed that type 1 diabetes is the result
of both genetic and environmental factors. These factors can lead to an
autoimmune reaction in which the pancreatic beta cells are destroyed, leading to
type 1 diabetes and a lifelong dependence on insulin.
In both children and adults, the rate of
progression from the onset of beta-cell destruction to glucose intolerance, and
then to symptomatic disease, is variable. We now know that this process can
last from only a few months to several decades.
With new and
ongoing studies, type 1 diabetes can be identified at earlier, pre-symptomatic
stages. The condition can now also be staged, starting with the detection of
two or more islet auto-antibodies in the blood (stage 1) and progressing at a
variable rate to a second stage of glucose intolerance or an abnormality in
blood-glucose stability (stage 2), before becoming clinically symptomatic
represents manifestations of the typical symptoms and signs of diabetes, which
may include frequent urination, excessive thirst, weight loss and fatigue.
Prognosis of type 1 diabetes
Untreated type 1 diabetes
is a fatal condition as a result of diabetic ketoacidosis – a complication that
is characterised by severe disturbances in carbohydrate, protein and fat
metabolism. Poorly controlled type 1 diabetes is a risk factor for chronic
complications such as blindness, renal failure, foot amputation, and heart attack.
But there is good news: in
type 1 diabetes, the incidence of microvascular disease (e.g. damage to the
smaller blood vessels) and macrovascular disease (e.g. damage to the large blood vessels) can be dramatically reduced with tight control
of blood-glucose levels.
If you manage to control
your condition well, the decreased incidence of macrovascular disease can persist
for up to 30 years. Even a few years of intensive glucose control translates
into reduced rates of microvascular and macrovascular complications 10 years
later. Most people with type 1 diabetes should aim to achieve and maintain a
target HbA1c of less than 7% to prevent microvascular disease.
(CVD), which falls into the macrovascular disease category, is a major cause of
death and morbidity in people with diabetes. CVD includes heart disease, stroke
and all other diseases of the heart and circulation, including hardening and
narrowing of the arteries supplying blood to the legs (peripheral arterial disease).
One analysis of people
with type 1 diabetes who were diagnosed before the age of 15 found that the
leading cause of death before the age of 30 years was acute complications of
diabetes. After the age of 30, CVD was predominant – although death
attributable to acute complications was still important in this age group.
Life expectancy is reduced, on average, by
more than 20 years in people with type 1 diabetes who have not controlled their
It’s also worth taking note of the risks
during pregnancy. Babies of women with type 1 diabetes are:
- Five times as likely to be stillborn.
- Three times as likely to die in their first few months of life.
- Twice as likely to have a
major congenital anomaly.
However, with careful planning and adequate treatment, most women with type 1
diabetes can have successful pregnancies.
Course of type 2 diabetes
Type 2 diabetes can be a
progressive disease in which the risks of macrovascular disease, microvascular disease
and death are all strongly associated with hyperglycaemia (elevated blood
The course of the disease
is characterised by a decline in beta-cell function and progressive insulin
resistance – when the cells in the muscles,
fat and liver don’t respond well to insulin and can’t easily take up glucose
from the blood.
The process involves the
degeneration of multiple parameters, including haemoglobin A1C (HbA1c), fasting blood glucose (i.e. your blood-glucose
levels after a period of fasting) and postprandial glucose levels (i.e. your blood-glucose
levels after consuming a meal).
In type 2 diabetes, the beta
cells in the pancreas fail to adjust to impaired glucose tolerance, which leads
to a decline in their function. Progressive loss of beta-cell function and, to
a lesser extent, reduced beta-cell mass, lead to worsening glycaemic control
and the development of complications.
Many of the current
therapies don’t completely stop this progressive loss of beta-cell function,
even though they lower blood-glucose levels, and unfortunately their use is
also associated with hypoglycaemia (low blood glucose) and weight gain.
Prognosis of type 2
By the time they’re diagnosed, 50% of people with type 2 diabetes already show
signs of complications. These complications may begin 5-6 years before
diagnosis, while the diabetes itself may start 10 years or more before the clinical
diagnosis is made.
CVD is a major cause of death and disability
in people with type 2 diabetes, accounting for 52% of fatalities in this group.
People with type 2 diabetes have a two-fold increased risk of stroke within the
first five years of diagnosis compared with the general population.
Other possible complications include:
- Kidney disease. Diabetes
is the single most common cause of end-stage kidney disease and about one
in three people with type 2 diabetes develop overt kidney disease. Kidney
disease accounts for 11% of deaths in people with type 2 diabetes.
- Depression. The
prevalence of depression is approximately twice as high in people with
diabetes as it is in the general population.
- Neuropathy (nerve damage). Damage to the nerves that transmit
impulses to and from the brain and spinal cord to the muscles, skin, blood
vessels and other organs may affect up to 50% of
people with diabetes. It can also cause erectile dysfunction and chronic pain.
- Limb amputation. Diabetes
is the most common cause of lower-limb amputation. About one in every 20 people
with diabetes will develop a foot ulcer in any given year and more than
one in ten foot ulcers result in the amputation of a foot or leg. Up to
70% of people die within five years of having an amputation as a result of diabetes.
Life expectancy is reduced, on average, by up to 10 years in people with type 2 diabetes.
Course of gestational diabetes
diabetes is a form of diabetes that causes high blood glucose levels during
pregnancy. If left untreated, it can lead to several complications for both
mother and baby. The
mother is at increased risk for pre-eclampsia, a condition characterised by
high blood pressure, and there’s an increased risk of birth complications, including
premature birth, still birth, macrosomia (a large baby), hypoglycaemia of the
newborn, jaundice and mineral deficiencies.
Researchers have found that women who gain
excessive amounts of weight later in pregnancy (between 28 and 36 weeks) are
more likely to have a difficult labour, requiring interventions such as forceps
delivery and instrumental delivery, which may lead to injury. The effects on the
baby are also more significant, with a greater risk of high birth weight.
The risk for complications is reduced
immensely with tight blood glucose control and weight management. In most
cases, the gestational diabetes is resolved after the baby is born.
Prognosis of gestational
A previous diagnosis of
gestational diabetes carries a lifetime risk of progression to type 2 diabetes.
In fact, women with a history of gestational diabetes are around seven times
more likely to develop type 2 diabetes than women who had a normal pregnancy. If
the woman with gestational diabetes needed insulin injections to control her
blood glucose during pregnancy, her risk for type 2 diabetes is further
When compared to women who don’t develop gestational
diabetes, women with a history of the condition are also at greater risk for CVD
events – especially heart attack – later in life. However, women who maintain a
healthy lifestyle throughout their middle years may reduce their CVD risk,
despite having a history of gestational diabetes.
The risk of a mother getting gestational
diabetes again in a future pregnancy is between 30% and 84%. If the second
pregnancy occurs within a year of the first, the risk of recurrence is higher.
Babies born to mothers who had gestational
diabetes are at greater risk of developing obesity and type 2 diabetes later in
Overall prognosis of
While diabetes can reduce a person’s life expectancy, it’s a condition that can
now be controlled with great success.
The general statistical prognosis is that 15%
of people with type 1 diabetes will die before the age of 40. But thanks to
advances in the understanding of the condition, this number is much lower than
it was a few decades ago. Sensible blood glucose control, along with a healthy,
active lifestyle, can help people with type 1 diabetes lead long, productive
A type 2 diabetes diagnosis in your 40s cuts 5-10
years off your average life expectancy. This is also a vast improvement on what
the prognosis used to be. Medical science has now also made it possible to live
a full, productive life with fewer complications if you’ve been diagnosed with
type 2 diabetes.
With both type 1 and type 2 diabetes, a multi-disciplinary
team approach is required to manage the condition effectively. It’s important
to look for a diabetes clinic that has dedicated, appropriately trained staff,
where you can do both individual consultations as well as group education
sessions. There should be adequate protocols that cover screening and regular care,
including referrals to other health professionals.
Apart from the recommended monitoring that
should be done at your clinic or doctor’s rooms, you should also be guided in
terms of vaccination (e.g. you may need to be vaccinated against influenza,
pneumococcal pneumonia and hepatitis).
You should go for a yearly dental examination and
visit the oral hygienist twice a year to control gum disease, which both contributes
to and worsens high blood glucose levels. Gum disease is more prevalent in
adults with type 2 diabetes and severe infections can lead to heart problems
which, in turn, affect life expectancy.
People with autoimmune diabetes are also more
likely to have thyroid disease, coeliac disease and depression. Talk to your
doctor about the symptoms of these diseases and don’t delay getting treatment
if you suspect you may be affected.
supplied by Jeannie Berg, diabetes educator and Chairperson of the Diabetes Education Society of South Africa (DESSA), and reviewed by Dr Joel Dave (MBChB PhD FCP Cert Endocrinology), Senior Specialist in the
Division of Diabetic Medicine and Endocrinology, University of Cape Town.