Too-Strict Glucose Control in Diabetes May Be Harmful

I’ve posted before about too-strict glucose control in type 2 diabetics – it can backfire.  Confirmation of this comes from a British article in the Lancet.

Two groups of type 2 diabetes patients aged 50 or older were enrolled and followed between 1986 and 2008. There were 27,965 patients whose treatment had been intensified from one oral antidiabetic drug to two or more oral drugs, and 20,005 who had switched regimes to include insulin injections.  Overall mortality was examined in relation to the HbA1c levels (the blood level of glycated hemoglobin that’s regarded as a good indicator of blood sugar levels over the previous weeks or months). The subjects were classified into 10 groups (or deciles) according to their HbA1c levels. 

During the 5 years after starting the more intensified therapy, there was a U-shaped curve in both groups: patients with the lowest HbA1c levels (average 6.4%) and those with the highest (10.6%) had significantly higher mortality rates than those at the middle level (7.5%).

A U-shaped (or J-shaped) response has been observed before – for instance with the number of hours of nightly sleep.  This sort of relationship is common in nature – “not too little, not too much” says it all.  Other examples include: body mass index (BMI) or waist circumference, alcohol consumption, blood pressure and blood cholesterol. This means one shouldn’t be too slavish in working towards the lowest HbA1c possible; 7.5% is most probably enough!