What are complications of Diabetes Mellitus?

The effects of diabetes manifest in nearly all organ systems of the body. If left untreated, diabetes can lead to heart disease, kidney failure, loss of vision, loss of foot etc. But what is cause of these effects of diabetes?

As you know, diabetics have higher blood glucose levels than do normal people. The excess blood sugar gets deposited in blood vessels of diabetics, which leads to two sets of complications both related to abnormalities in blood vessel

Microvascular complications:

These complications are due to abnormalities in small blood vessels. They are:

  1. Diabetic retinopathy affecting the eyes/vision: Studies have reported that after 20 years of having diabetes type 2, 60% of patients develop retinopathy.  Proliferative forms (more severe) of retinopathy can lead to vision loss, which is a common cause of blindness.
  2. Diabetic nephropathy affecting the kidneys: it is the leading cause of end stage kidney disease in Indians. Diabetics who also have high blood pressure and cholesterol or those who smoke are more likely to get diabetic nephropathy. First there is small amounts of albumin in urine, which if left untreated will lead to kidney failure in 20-40% of people
  3. Diabetic neuropathy affecting the nerves of heart, gastrointestinal system, genitourinary system and nerves of legs, is often the first symptom of diabetes type 2 in India.
    • Peripheral neuropathy can progress to ‘diabetic foot‘ in which the sensations and the blood supply in feet is reduced. Therefore, the patient is not able to sense trauma and develops sores and ulcers, which get infected and may progress to gangrene. Diabetic foot is a common cause of amputation
    • Other manifestations of diabetic neuropathies are erectile dysfunction, constipation, feeling of fullness, increased frequency of urine etc

Macrovascular complications or CVD (cardiovascular disease):

These are due to abnormalities in bigger blood vessels including those supplying the heart. These include, Ischemic Heart Disease (IHD or CHD), Carotid Artery Disease (CAD), Peripheral Artery disease (PAD) and their complications such as MI or heart attack, stroke, gangrene of legs etc.

CVD is the leading cause of death in diabetics and diabetes is considered to confer ‘very high risk’ for heart disease

How does good control of blood sugar help in avoiding these diabetic complications?

Many studies have looked into the effect of good control of blood sugar levels on these complications in type 1 and type 2 diabetes. Some of these are

  • The ‘Diabetes Control and Complications Trial’ (DCCT) study in patients with type 1 diabetes
  • The’ Epidemiology of Diabetes Interventions and Complications’ (EDIC) study, a follow up study on patients in DCCT study
  • The UK Prospective Diabetes Study (UKPDS)
  • The Kumamoto Study
  • The ‘Action to Control Cardiovascular Risk in Diabetes’ (ACCORD) study,
  • The ‘Action in Diabetes and Vascular Disease: Preterax and Diamicron MR Controlled Evaluation’ [ADVANCE], and
  • The ‘Veterans Affairs Diabetes Trial’ (VADT)

The results of these studies are summarized below:

Microvascular complications:

  1. In DCCT study, it was found that people whose blood sugar was kept under tight control developed fewer complications that those with standard treatment
  • Diabetic eye disease started in only one-quarter as many people in tight control group
  • Kidney disease started in only half as many people
  • Nerve disease started in only one-third as many people
  • Far fewer people who already had early forms of these three complications got worse
  1. The EDIC study confirmed that these benefits were sustained over a period of five years; even when some patients in ‘tight control’ group could only maintain HbA1c comparable to standard group during follow up
  2. The Kumamoto and UKPDS studies found similar benefits in type 2 diabetics.
  3. The ACCORD, ADVANCE and VADT studies found that HbA1c levels lower than 7 were further associated with prevention or better control of microvascular complications

Macrovascular complications:

  1. In the DCCT, there was a trend toward lower risk of CVD events with tight control. In the 9-year follow-up of the EDIC study the tight control group had a  57% reduction in the risk of nonfatal myocardial infarction ( heart attack), stroke, or CVD death compared with the standard group, and recently this effect has been shown to last for several decades
  2. During the UKPDS trial, there was a 16% reduction in CVD events (combined fatal or nonfatal MI and sudden death) in the tight control group, a follow up period of ten years found these benefits to be even more
  3. The ACCORD, ADVANCE and VADT studies, which were done on patients with long standing diabetes (8-11 years or more), often with existing CVD, found no such risk reduction

In summary

Tight control of blood sugar (HbA1c levels less than 7% and less than 6.5%, if possible) results in lesser microvascular complications in all diabetics. For CVD risk reduction, tight control in the initial years of diabetes is most beneficial

To know more about what does tight control actually mean, read ‘What does good control of blood sugar mean in diabetes?’

Also, diabetes experts recommend frequent monitoring of diabetic patients by blood tests and physical examination to detect and treat early the complications of diabetes as well as to ensure good control, get the complete list of routine tests for diabetics

CHECK OUT:Our references for diabetes mellitus