Diabetes is a condition characterised by higher-than-normal levels of sugar (glucose) in the bloodstream. One problem here is that there is more tendency for glucose to react with proteins and fats in the body (through a process known as glycation) that can damage tissues. The complications of diabetes, including nerve, vessel, eye and kidney damage, generally have their roots in glycation.
So, it makes sense then keeping blood sugar levels in check should help to prevent the complications of diabetes. So important is this deemed to be, that the UK government gives general practitioners (GPs) money to ‘incentivise’ them to assist their patients in achieving relatively tight control over their blood sugar levels. From April of this year, if GPs can get half of their type 2 diabetic patients to have a HbA1c level (this is a measure of blood sugar control over the preceding 3 months or so) of less than 7 per cent, then the practice gets an additional payment of £3000 ($4250). Prior to this, the target set by the government was 7.5 per cent. Clearly, the government feels that when it comes to HbA1c levels, lower is better.
I imagine that not everyone will be comfortable with the notion of doctors being financially incentivised to treat patients in a way deemed appropriate by their government. But, these individuals at least can take comfort in the fact that the government’s strategy is ‘evidence-based’. However, as a recent piece in the British Medical Journal [1] points out, this is far from assured.
In this piece, the authors (one a UK GP and the other a professor of medicine, epidemiology and public health in the USA) detail the results of three recent studies which suggest that tighter control of blood sugar by pharmacological means may not be such a good idea. One of these trials [2] I reported on here. It showed a higher mortality rate in individuals who were more intensively treated. The other two studies cited [3,4] showed little or no differences in outcomes.
All of the studies found intensive treatment to be associated with an increased risk of hypoglycaemia (low blood sugar). The authors summarise the findings of these three studies thus: Taken together, the three trials show that no reduction of clinically meaningful adverse outcomes occurred in patients with long standing type 2 diabetes treated to a glycated haemoglobin below 7.0% in the time periods studied. Moreover, intensive treatment is accompanied by substantial costs and an increased risk of hypoglycaemia and perhaps mortality.
The authors point out that these studies were done in older individuals (mean age 60+) with quite long-standing illness. There is some evidence that more intensive therapy in younger individuals (mean age 54) with newly diagnosed diabetes [5]. Nevertheless, the authors argue, the current state of the evidence gives us enough reason to reconsider the conventional wisdom regarding blood sugar control in type 2 diabetes.
They bring up another interesting point too, when they question whether all strategies that reduce HbA1c levels have the same effect. Even for a given level of blood sugar lowering effect, different drugs or combinations of drugs may have very different effects on the outcomes that matter (like risk of disease and death). As they point out, our knowledge in this area is quite unsatisfactory.
It seems that not only is the UK government’s recent move to lower the HbA1c targets for GPs not particularly evidence-based, there is a risk it might actually do more harm than good. The authors of the BMJ piece use some good old-fashioned plain-speak to conclude their piece by stating: The change of target from 7.5% to 7% should be withdrawn before it wastes resources and possibly harms patients.
References:
1. Lehman R, Krumholz HM. Tight control of blood glucose in long standing type 2 diabetes. BMJ 2009;338:b800
2. Action to Control Cardiovascular Risk in Diabetes Study Group. Effects of intensive glucose lowering in type 2 diabetes. N Engl J Med 2008;358:2545-59.
3. ADVANCE Collaborative Group. Intensive blood glucose control and vascular outcomes in patients with type 2 diabetes. N Engl J Med 2008;358:2560-72.
4. Duckworth W, et al. Glucose control and vascular complications in veterans with type 2 diabetes. N Engl J Med 2008;360:129-39.
5. Holman R, Paul S, Bethel MA, Matthews D, Neil A. 10-year follow up of intensive glucose control in type 2 diabetes. N Engl J Med 2008;359:1577-89.
