Dr Aidin Rawshani

Complications of type 1 diabetes


Type 1 diabetes leads to complications — blood sugar is crucial

This chapter deals with complications (sequential diseases, consequences) of type 1 diabetes. Knowledge of these complications is important for those who have type 1 diabetes, as it is possible to prevent, or at least postpone, these complications through careful control of risk factors. However, one should know that our knowledge of these complications develops constantly.

Before 1922, there were never any complications of diabetes (complications of type 1 diabetes), as no patients could survive long enough for complications to occur. At that time, all patients died shortly after the onset of the disease and this was the result of the acute condition of ketoacidosis, which today has become a rare cause of death among people with type 1 diabetes.

In 1922, insulin was introduced by Fredrick Banting and Charles Best, so people with type 1 diabetes could suddenly survive. Today — almost 100 years later — type 1 diabetes is a fairly common disease affecting both children, young people and adults. We have learned an incredible amount about the disease, effective treatments and the importance of controlling risk factors. Today, people with type 1 diabetes can become 80 years or even older.

Despite these successes, the life expectancy of people with type 1 diabetes is on average 11 years shorter than people without the disease. This is explained, according to thousands of studies, by the sharply increased risk of cardiovascular disease. People with type 1 diabetes have chronically elevated blood sugar and this leads to damage to the vessels, which in turn affects the organs (which depend on the vessels).

The damage that occurs as a result of high blood sugar is called “complications”, or “diabetic complications”.21

Microvascular and macrovascular complications in type 1 diabetes

The complications that arise are divided into two types:

  • Microvascular complications — These complications are due to the fact that the smallest vessels of the body are damaged by high blood sugar.
  • Macrovascular complications — These complications are due to the fact that large vessels can also suffer from high blood sugar.

Microvascular complications

These complications are very typical for people with high blood sugar. People without high blood sugar in principle do not suffer from this kind of complications. Microvascular complications include kidney damage, nerve damage and damage to the retina.

Kidney damage – High blood sugar damages the kidneys. In medical language, this is called nephropathy.

Nerve damage — High blood sugar damages the nerves of the body and this is called neuropathy. This may be marked, for example, as a loss of sensation (possibly pain) in the feet and legs.

Injuries to the retina — The retina is crucial for us humans to see. High blood sugar leads to damage to the retina and hence loss of vision (visual impairment). This is called retinopathy.

Nephropathy, retinopathy and neuropathy all depend on high blood sugar. This means that the risk of these complications increases with high blood sugar, and likewise reduces the risk if blood sugar can be controlled.

Macrovascular complications

These complications are not unique to people with type 1 diabetes, but they can also affect the rest of us. Unfortunately, people with type 1 diabetes have a markedly increased risk of these complications. The most common of the macrovascular complications is varicose dilatation (atherosclerosis) of the heart vessels and this leads to coronary heart disease.

Myocardial infarction

People with coronary heart disease may suffer a heart attack. People with type 1 diabetes have several times increased risk of coronary heart disease and heart attack, and this is because the high blood sugar makes these people have more aggressive atherosclerosis.22


Stroke (apoplexy) is also a macrovascular complication, and people with type 1 diabetes have a 3 times increased risk of stroke, compared with people without type 1 diabetes.23

Heart failure

Heart failure was a complication that flew under the radar for many years. Today we know that people with type 1 diabetes have a significantly increased risk of heart failure and this is also considered explained by high blood sugar. People with type 1 diabetes have almost 5-fold increased risk of heart failure, compared with people without type 1 diabetes.24

Life expectancy in type 1 diabetes

In a large Swedish study, the largest of its kind, more than 30,000 people with type 1 diabetes were followed and it was found that during the study, people with type 1 diabetes had 2 to 4 times increased risk of dying. The increased risk is mainly explained by mortality from cardiovascular disease.25

In a study from Scotland, it was estimated that this leads to a shorter life expectancy for people with type 1 diabetes compared to people without type 1 diabetes.26

The cause of complications of type 1 diabetes

There is no doubt that high blood sugar is the cause of microvascular complications (kidney damage, nerve lesions, damage to the retina) in type 1 diabetes. The same complications are observed even in type 2 diabetes, which is also characterized by high blood sugar. There are many ways to measure blood sugar (fasting blood sugar, fluctuations in blood sugar, long-term blood sugar).

Today, most clinics and scientists agree that HbA1c (long-term blood sugar) is an excellent marker of how the blood sugar level lies. Long-term blood sugar (HbA1c) reflects how high blood sugar has been in the last 6 weeks.27

High blood sugar is especially harmful to three tissues

  1. Retina
  2. Nerves
  3. Kidneys (damage to glomeruli that are small structures of the kidneys that filter the blood)
  4. Small blood vessels (microvascular damage)

A hypothesis about how high blood sugar damages our blood vessels

These three sites have a common denominator: the cells of these tissues are not able to regulate their absorption of sugar (glucose). This means that when blood sugar rises (which does in type 1 diabetes), these cells take up more glucose. This means that the concentration of sugar (glucose) becomes too high inside the cells and they fail to reduce their absorption of glucose. This leads (it is believed) to the production of harmful substances (superoxides) inside the cells. These superoxides lead to damage to the cells (this process is called “oxidative stress”).

It is believed today that both microvascular and macrovascular complications are the result of oxidative stress, which, in turn, is caused by high blood sugar. In addition, it has been seen that this leads to a decrease in the production of two important enzymes (NO synthase, prostacyclin synthase). These enzymes are important to counteract the onset of atherosclerosis (varicose veins, atherosclerosis). High blood sugar is the most important explanation for this! 28

How important is good blood sugar control?

Glycemic control is the medical term for sugar control (blood sugar control). Good glycaemic control means managing to keep blood sugar as far as possible, without risking serious blood sugar falls (hypoglycaemia). Good glycemic control is crucial for preventing complications of type 1 diabetes.

In fact, studies show that the whole 95% of the risk of complications can be explained by blood sugar.Well-made randomized controlled clinical trials show that good glycaemic control reduces the risk of complications. The best-known study called DCCT, which noted that intensive glycaemic control reduced the risk of microvascular complications by 35 -76%, and macrovascular complications decreased by as much as 58%! 30

It was also found that the benefits of intensive glycemic control lasted many years after the end of the study. Intensive glycaemic control is equally important in type 2 diabetes. Although studies show that people with type 2 diabetes do not appear to have immediate benefit from intensive glycaemic control, they are highly likely to benefit in the long run (by reducing their risk of microvascular and macrovascular complications).31

Now we will go through the microvascular and macrovascular complications one at a time.

Retinopathy: damage to the retina leads to visual impairment

Retinopathy means that the retina becomes damaged and this leads to visual impairment. This is a consequence of changing the blood vessels of the retina. The vessels become dilated in certain places, they leak liquid and can even bleed. In addition, it becomes many more vessels than normal. Overall, this leads to damage to the retina, resulting in impaired vision.

Individuals with type 1 diabetes are also at increased risk of cataract and glaucoma.32

Fortunately, there is effective treatment in the form of laser therapy (photocoagulation) that can slow down these changes in the retina.

Individuals with type 1 diabetes must therefore regularly undergo retinal examination to detect retinopathy early, as this will slow down damage early in the process. 33

Nephropathy: kidney damage that can lead to renal failure

Diabetes nephropathy is actually the world’s most common cause of chronic renal failure (however, the majority of people with diabetes and renal failure have type 2 diabetes). Nephropathy means that the functioning of the kidneys is impaired. This can be detected by measuring the concentration of a protein in the urine. This protein is called albumin and if you secrete too much albumin it is a sign of nephropathy. The more albumin one secretes, the more pronounced the nephropathine is.

In medical language, the term albuminuria is used to describe the presence of albumin in the urine. The name microalbuminuria is used if the concentration of albumin in the urine is between 30 and 299 mg/day. The term macroalbuminuria is used if you secrete 300 mg or more albumin per day. The concentration of albumin in the urine must be measured on everyone with diabetes at least once every year.

The presence of protein (albumin) in the urine is a strong risk factor for two conditions:

  1. Renal damage
  2. Nephropathy
  3. Increased risk of cardiovascular disease

It is quite easy to understand why albuminuria is associated with an increased risk of renal failure (chronic kidney failure); after all, albumin in the urine is a symptom that the kidneys are affected. However, it is unclear why albuminuria/nephropathy is associated with such a high risk of cardiovascular disease. However, today we know that the risk of renal failure and cardiovascular disease gradually increases with the concentration of albumin in the urine (that is, the more albuminuria, the higher the risk).

How common is nephropathy and albuminuria?

A Danish study showed that a third of people newly diagnosed with type 1 diabetes develop microalbuminuria within 20 years.35 These figures are similar to those published by the Swedish National Diabetes Register. Approximately 40% of people with microalbuminuria receive macroalbuminuria within 10 years.

However, it should be mentioned that some people with microalbuminuria never develop macroalbuminuria. Probably, good glycemic control, careful control of blood pressure and the use of statins are a success factor.37

How serious is nephropathy?

In the worst case, neuropathy can lead to kidney failure and need for dialysis.

Neuropathy: damage to nerves

Damage to nerves is called neuropathy. The most common type of neuropathy is the one that affects nerves in the limbs, but nerves that go to our internal organs can also be affected (these nerves are called autonomic nerves).

The neuropathy that affects the nerves of the limbs is often called peripheral neuropathy. It usually affects the feet and legs first, and after some time the hands and arms are also affected. Symptoms of peripheral neuropathy are most often the worst at night and include the following:

  • Feeling sick, feeling that feet/legs/hands/arms are numbness.
  • Down ability to feel warmth and cool
  • In the skin feels a tingling or burning sensation
  • Man may experience sharp pain or cramp
  • You can become sensitive to deprived, as it hurts when someone takes on the skin
  • Reflexes become less active
  • The balance gets worse, as well as coordination

If autonomic nerves are affected, it may be nerves that go to the heart, blood vessels, lungs, eyes, urinary organs or gastrointestinal tract. If the heart’s nerves are affected, it can lead to poor condition, a drop in blood pressure, higher blood pressure (especially at night), a particular type of oxygen starvation of the heart, high heart rate, low heart rate or reduced heart rate variability. 38

Here are the most common signs/symptoms of autonomic neuropathy:

  • Low blood sugar levels do not feel as much as they did before (hypoglycaemia give less symptoms).
  • The bladder works worse, which makes it more frequent to urinary tract infections, urinary cornices or incontinence.
  • Constipation, diarrhea or both.
  • The stomach is emptied more slowly (gastroparesis), which leads to dizziness, vomiting and impaired appetite.
  • It may become more difficult to swallow
  • Erectile dysfunction in men.
  • The vagina does not become as moist and thus they become more difficult to conduct sexual intercourse.
  • Man can sweat more or less than normal.
  • Blood pressure can not be regulated as well, which can lead to a drop in blood pressure when a man
  • If you get up and then you get dizziness or you faint in the worst case.
  • Regulating body temperature gets worse.
  • The eyes get harder to adapt to the dark.
  • You may have an abnormally high heart rate while resting.

Macrovascular complications

People with type 1 diabetes have 2 to 8 times increased risk of cardiovascular disease and death. Atherosclerosis is more aggressive in people with type 1 diabetes, compared to people without the disease. Heart failure, heart attack and stroke are the most serious macrovascular complications. Good glycaemic control is essential to minimise the risk of these serious complications. 39

Of all macrovascular complications, coronary heart disease is most common. Ischemic heart disease is due to atherosclerosis of the vessels of the heart and this can lead to a heart attack. Men with type 1 diabetes have a 3 times increased risk of coronary heart disease, compared to men without type 1 diabetes. Women with type 1 diabetes have up to 7 times increased risk of coronary heart disease, compared to women without type 1 diabetes.

Peripheral artery disease (vascular disease)

Peripheral vascular disease means atherosclerosis (atherosclerosis, atherosclerosis) of the arteries of the legs. This can lead to the tissue getting oxygen starvation and not being able to cope. In a study involving 65-year-old people with type 1 diabetes, 11% of women had undergone amputation and the corresponding figures for men were 20%. However, this study is old and probably it is rarer today.40

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