The long term complications of diabetes involve many different systems in the body. These may be found at time of diagnosis of diabetes, or many years after the onset of diabetes. Many of the long term complications of diabetes are thought to be due to persistently elevated levels of blood glucose and it has been shown, that controlling blood glucose levels and blood pressure may minimize or prevent the onset of these complications.
It is difficult to predict who is likely to develop chronic complications of diabetes which may sometimes occur regardless of the level of control.
The complications of diabetes may be categorised as
It is unusual for people with type 1 diabetes to have complications such as retinopathy and nephropathy within the first five years of their diabetes.
Studies have shown that the risk of kidney damage and eye disease are more common in people with poor control. This risk rises steeply above HbA1c values of 9% and is highest if the HbA1c value is above 12%.
The Diabetes Control and Complications Trial (DCCT) showed that 12% of people Type 1 diabetes who were intensively treated (tight control) developed new retinopathy changes after nine years, compared to 54% of people who were treated with conventional (less tight control) methods. Progressive retinopathy was uncommon at HbA1c levels below 7%. People with very mild retinopathy were also less likely to progress to severe retinopathy if they were well controlled.
Similar observations have been made for diabetic nephropathy. Once retinopathy or nephropathy are well established, tight control is unlikely to provide a significant benefit. Prevention of complications is therefore desirable in people with Type 1 diabetes by tight control, started early, in suitable people.
The main concern in Type 2 diabetes, is with regard to the risk of vascular complications. This form of diabetes carries a heightened risk of heart attacks, stroke and circulatory problems.
The United Kingdom Prospective Diabetes Study showed that high blood glucose concentrations contribute to the risk of small vessel disease in type 2 diabetes as well. The researchers examined over 4000 people with type 2 diabetes, once again looking at the effects of 'intensive' and 'conventional' treatment. Over a period of ten years, people in the intensively treated group, who had an HbA1c level of 7.0% (compared to 7.9% in the conventional treatment group) were found to have a 25% risk reduction in complications such as eye and kidney disease.
No, not everyone who has diabetes will develop complications. There is good evidence that good control of blood sugar, blood pressure, cholesterol lowering, a healthy lifestyle with plenty of exercise and no smoking will prevent complications in most people.
Acute complications of diabetes usually resolve completely with treatment.
Once the chronic complications of diabetes are extablished, they rarely resolve completely. The best counsel therefore, is that of ‘prevention’. Much can be done to alleviate the problems associated with chronic complications of diabetes.
Dr Nishan Wijenaike MD, FRCP
West Suffolk Diabetes Service
Updated November 2007