Exploring the Clinical Utility of a Novel Metric of Between-day Glycemic Variability

Abstract Introduction: In people with type 1 diabetes (T1D) using continuous glucose monitoring, we have observed that the 5 th –95 th centiles (interventile range [IVR]) can be compared with the 25 th –75 th centiles (interquartile range [IQR]), reflecting the greater but less common excursions with more common but lesser variability. The relationship between IVR and IQR has not been explored in existing measures of glycemic variability. Materials and Methods: We calculated what we have termed the social/typical (ST) ratio by the formula (IVR−IQR)/IQR, across different time periods: total (0000–2400), daytime (0600–2400), and nighttime (0000–0600). We explored its relationships with other glycemic metrics and diabetes complications in two T1D datasets: (i) a randomized, controlled exercise intervention study in overweight adults and (ii) a cohort of older adults, where a recent history of severe hypoglycemia was common. Results: In cohort (i) at baseline, higher total ST was present in those with nephropathy ( P = 0.013), and higher nighttime ST was present in any retinopathy ( P = 0.009). Nighttime ST rose significantly postexercise intervention (mean ± standard deviation from 1.04 ± 0.27 to 1.44 ± 0.52, P = 0.008). There was a strong positive correlation between total ST and time below range (TIR) following exercise intervention ( r = 0.480, P = 0.018). In cohort (ii), total ST was positively correlated with TIR ( r = 0.320, P < 0.001) and negatively with time above range ( r = −0.277, P < 0.001). Higher coefficient of variation ( P = 0.014) but not ST was associated with a recent history of severe hypoglycemia. Conclusions: ST, a novel and dynamic metric of between-day glycemic variability, is modifiable by lifestyle intervention, correlates with established glycemic measures, and may link to microvascular complications.