HbA1C and Retinopathy

• the relationship between HbA1c and retinopathy
• ideal HbA1c targets
• what does this mean in practice?
• a graph...linear relationship
• sudden improvement in control
• ACCORD
• HbA1c to glucose converter (link)
  

Controlling your diabetes can slow down diabetic complications and retinopathy. In practice this means that conditions such as retinopathy may stopped in most people, and good sight maintained.

In a few people the retinopathy may still progress, but at a much slower rate. See DCCT and UKPDS.

 

Relationship between HbA1c and retinopathy

The progression rate of retinopathy is 37% less for each 1% reduction in the HbA1C or 1mmol/l of blood sugar. Teamwork is crucial to good diabetic control: the patient is the focus, but assistance from many health professionals is usually needed to assist good control.

 

Ideal Targets for HbA1c

if well, and diet or tablet controlled	HbA1c less than 6.5%
if very ill	higher levels may be accepted
if using insulin and keen to control diabetes and able to test glucose 4-6 times day (basal bolus insulin/pump)	HbA1c 6.5-7.5% (without many hypos)
if using insulin and keen to control diabetes and able to test glucose <4 times day (basal bolus insulin/pump)	HbA1c 7.0-7.5% (or as low as possible without many hypos)

A recent paper indicates that health is best for patients with an HbA1c of 7.5%. Any lower may actually increase problems. This was particulary so for insulin users, for those who have switched to insulin (Lancet 2010). Similarly higher HbA1c values increase risk.

 

What does this mean in practice?

This means that if your diabetes is controlled (HbA1c less than about 7%) retinopathy may never develop, or develop very slowly.

Such good control is easier to achieve if your have type 2 diabetes and use tablets. Eventually though, the pancreas stops producing any insulin and eventually most people with type 2 diabetes eventually need insulin, and then control is harder.

Whatever your type of diabetes, if you use insulin, such good control is harder to achieve. But the lower the better, so if your HbA1c is 7.0%, you will develop retinopathy at a much slower rate thatn someone whose level is 9.0%.
As each percentage point of HbA1c translates into a massive 37% difference in progression rate, your retinopathy will be 2 x 37%, = 74% slower, to develop.

Retinopathy may develop after 14 years of poorly controlled type 1 diabetes (type 2 less than 14 years as it may be diagnosed late).

This page shows how you can convert your glucose readings into an approximate HbA1c value.

 

Enlarge If your HbA1C is 7% retinopathy may develop, but it is much slower to develop than if it is 9%. If your HbA1C is 7%, you will have about 74% less progression after 2 years than if it is 9%. Blue...no retinopathy;        red... retinopathy  

A graph

What is your HbA1c? Is it below 7.5%? If not, can you get it lower? Ask your nurse for help.

 

 

 

 

 

 

Sudden improvement in your control

If you suddenly improve control and your HbA1C drops the retinopathy may need laser treatment. The benefits of an HbA1C drop, say from 9 to 7%, are long term. The retinopathy may actually deteriorate in the short term, and so require laser. If this is difficult to understand, ask your ophthalmologist to explain.
After two-three years however, assuming you have any laser that may be necessary, you will be better off and the retinopathy will be less active than it would otherwise have been. Retinopathy progression detail.

 

ACCORD ...type 2 and HbA1c <6.5%

Thed ACCORD  study noticed extra deaths in the very intensive glucose control arm. This group of patients had to achieve HbA1c <6.5%, and risks were increased 25 % versus the group that achieved 7.0-7.9%.

What does this add? We know from Steno  that "In at-risk patients with type 2 diabetes, intensive intervention with multiple drug combinations and behaviour modification had sustained beneficial effects with respect to vascular complications and on rates of death from any cause and from cardiovascular causes" . UKPDS   and DCCT showed similar benefits.

Comparing the two studies:

• 160 patients in total in Steno 2
• In Steno 2 only 20% achieved <6.5%...this was the target of the very tight ACCORD group
• In Steno 2 there was a mean 0.7% difference between the intervention group and the 'control' group , with a mean HbA1c of 8%,
• Steno 2 : benefit continued after intervention
• 7-7.9% is still very good control...as achieved in Steno 2
• ACCORD the tight control group <6.5%…had 25% more deaths versus the standard group 7-7.9%
• In ACCORD the tight BP control (BP below <120) and lipid control showed only benefit.

So what was the cause of the extra deaths in the ACCORD group? Reports such as BMJ suggest that

• very intensive glucose control (as a target <6.5%) may not be ideal if patients have CVD (cerebrovascular disease) and have been diabetic 10y, until we know more
• the problem may have been caused by the combination of multiple dose insulin regimes AND hypoglycaemic agents
• this is possibly because of hypos on the heart QT interval
• we should aim for this level if it can be achieved easily...eg in the first 10y of diabetes