Controversies for Glucose Control Targets in Type 2 Diabetes: Exposing the Common Ground

Glycated hemoglobin targets have been given in guidelines for the last three decades, mostly without change at around 6.5-7.0% (47-53 mmol/mol). Personalization of such targets has also long been advocated, but often with little and inappropriate guidance. More recently some have suggested higher targets might be indicated, and more specifically lower targets avoided, even in those in whom they are easily attained without seeming burden or risk. Prospective data from randomized and observational studies, in people with type 2 diabetes and indeed those without diabetes, find cardiovascular and mortality risk are uniformly lowest at lower levels including into the normal range. In some studies with large populations, a high proportion of people are found to attain such levels, and the UK Prospective Diabetes Study (UKPDS) and more recent studies appear to confirm the importance of starting low and continuing long. Studies of cardiovascular events and mortality in people with diabetes will already factor in any effect of hypoglycemia, which therefore should not be double-counted in setting targets. Nevertheless, some factors should lead to modification of target levels, and these will include experience of hypoglycemia where therapy change and glucose monitoring cannot ameliorate it and sometimes prospectively in those at social or occupational risk. The fact that clinical experience will modify targets emphasizes that targets will not be stable over time but will change, for example, with occurrence of adverse events or perceptions of increase/decreased burden of therapy. The evidence suggests that glucose control takes 5 years or more to have any impact on vascular outcomes or mortality, so targets may also be higher in those with shorter life expectancy or higher health burden or simply reflect individual preferences. This article discusses the evidence behind these conclusions.