Findings published in the British Medical Journal showed that the risk of complications associated with type 1 diabetes can be kept to a minimum by maintaining an HbA1c below 7% (53 mmol/mol) – although having an HbA1c lower than 6.5% (48 mmol/mol) was associated with an increased risk of severe hypoglycaemia and severe retinopathy.
As many people with type 1 diabetes spend time and effort to keep their blood glucose at or below the recommended 6.5% target in order to avoid complications, these findings suggest people achieving an HbA1c between 6.5% and 6.9% (48-52 mmol/mol) can also avoid increased risks of complications.
Why did they do this research?
Glycated haemoglobin – also known as HbA1c – is a measurement of average blood glucose level. In type 1 diabetes, high HbA1c levels increase the risk of complications such as retinopathy (damage to the blood vessels supplying the retina) and kidney disease, therefore people with type 1 diabetes are recommended to aim for an HbA1c of 6.5% or lower.
For some, reaching lower HbA1c levels can be stressful and time-consuming – and can also increase the frequency of hypos – and so the team of scientists decided to see how a slightly higher HbA1c of 6.5%-6.9% affected the risks of developing complications compared to other HbA1c levels.
What did they do?
Using the Swedish Diabetes Registry, the team took the data of almost 10,000 children and adults with type 1 diabetes and monitored them until the end of 2017. Monitoring was for anywhere between eight and twenty years, depending on when they were signed up to the registry. They analysed HbA1c for each participant and put them in five categories ranging from low HbA1c (6.5% or lower) and high HbA1c (higher than 8.6%, or 70 mmol/mol).
Using the monitoring, the team estimated their risk of retinopathy and kidney disease in relation to their HbA1c, and also noted episodes of severe hypoglycaemia within the different groups.
What did they find?
Compared to participants with an HbA1c between 6.5% and 6.9%, people with HbA1c of 7% and over had an increased risk of developing retinopathy and early kidney disease. However, people with an HbA1c level of 8.6% or higher had an increased risk of developing more severe forms of retinopathy and chronic kidney disease.
Importantly, people with an HbA1c 6.5% or lower were also at an increased risk of severe hypoglycaemia and of developing severe retinopathy. The team suggested that the two could be linked, as some studies have suggested that frequent episodes of hypoglycaemia could result in damage to blood vessels as seen in retinopathy.
What does this mean for type 1?
Shedding new light on risks associated with having low HbA1c, these findings suggest that people with type 1 may be able to minimise the risks of developing complications by keeping at HbA1c levels between 6.5% and 6.9%. While the current benchmark of 6.5% or lower also helps people to avoid these risks, this study suggests that this HbA1c may also put some people at risk of experiencing severe hypoglycaemia and retinopathy.
While it is useful, HbA1c is just one way of measuring blood glucose management in type 1 diabetes. Time in range and glucose variability are also important, as well as general quality of life as discussed here. We therefore recommend that any changes to personal HbA1c targets be discussed with healthcare practitioners.