Time in tight range: A key metric for optimal glucose control in the era of advanced diabetes technologies and therapeutics

Compared to glycated haemoglobin A1c (HbA1c), the rapidly developing continuous glucose monitoring (CGM) technology provides more detailed information about glycemic control. Amongst the new glucose metrics derived from CGM, time in target range of 3.9-10.0 mmol/L (time in range, TIR) has been widely used for the assessment of glucose control. In recent years, the rise of new technologies and therapies including advanced hybrid closed-loop automated insulin delivery systems and new hypoglycemic drugs has made it possible to achieve better glycemic control. In this context, the concept of time in tight range (TITR), defined as the percentage of time spent in target glucose range of 3.9-7.8 mmol/L, has gained increasing attention. Whilst TITR is highly correlated with TIR, there are still differences between the two metrics. These differences make TITR a more appropriate indicator in certain situations, such as when glucose levels are close to normal or when tighter glycemic control is required. This review summarizes recent studies related to TITR.