Eleen Schupp¹, Rinke Stienstra¹, Cees J., Tack¹, Rick I. Meijer¹

¹Department of Internal Medicine, Radboudumc, Nijmegen

Eleen.Schupp@radboudumc.nl

Background: Glycemic variability (GV) describes the fluctuations in blood glucose levels and may be relevant for the development of complications. However, GV itself can vary as well. The current guideline is to calculate GV over a period of two weeks, but it remains unclear whether the timing of this period impacts the GV. The goal of this study was to determine the effect of different days of the week, week vs weekend, different months and different seasons on GV metrics.

Methods: Glucose measurements from continuous glucose monitors of 262 participants with type 1 diabetes over the complete year 2023 were collected. The coefficient of variation (CV), time in range (TIR), standard deviation (SD) and mean were calculated per day and grouped per day of the week, week vs weekend, per month and per season. One-way ANOVA was used to test whether these subdivisions had a significant effect on the different GV metrics.

Results: The different days of the week, week vs weekend, months, and seasons, all significantly affected CV, TIR, SD and mean (p<0.001 for all groups and metrics, except for SD grouped by season p=0.03). CV was the highest on Saturdays, in weekends, in June and in summer. TIR was the lowest on Sundays, in weekends, in December and in winter. SD was the highest on Saturdays, in weekends, in December and in winter. Mean glucose was the highest on Sundays, in weekends, in December and in winter.

Discussion: Different days of the week, weeks vs weekend, different months and different seasons all have a significant effect on the GV metrics. While these differences are significant, they are also small, and thus the clinical significance should be the topic of further research. Nevertheless, for scientific studies aimed at the importance of GV, it appears important in what exact timeframe this parameter is calculated.