The recognition that diabetes is an independent risk factor for cardiovascular disease has led to trials of different glucose lowering strategies in an attempt to reduce the risk of such disease. The effect of glucose lowering on cardiovascular disease outcomes is one of the most contentious in recent history, as indicated by the class IIb recommendation from the joint American Diabetes Association, American Heart Association, and American College of Cardiology guidelines.1 In the linked meta-analysis (doi:10.1136/bmj.d4169), Boussageon and colleagues assess both microvascular complications and cardiovascular events related to the intensity of glycaemic control and the quality of randomised studies.2

Before considering individual trials several factors warrant consideration. For example, it is possible that glucose lowering is a much weaker intervention than previously envisaged so that individual trials may be underpowered to detect changes in a chosen end point. Also, current treatments may partly negate any benefit of glucose lowering by exchanging one risk factor for another—for example, weight gain, which has concomitant effects on blood pressure and lipids.3

The largest study to date, which compared the effects …