Glucose variations have a bidirectional relationship with the sleep/wake and circadian systems in type 1 diabetes (T1D); but the mechanisms remain unclear. Recent research published in ‘Scientific Reports’ described the coupling between glucose and unstructured physical activity over 168 h in patients with T1D.

Research grade actigraphy is a tool clinicians and researchers can use to examine sleep and circadian patterns through an economic non-invasive home assessment over an extended period of time. Participants were instructed to continuously wear the Spectrum Plus (actigraphy) on their non-dominant wrist continuously for 7–14 days and depress the event marker at "lights out" and "lights on" times to demarcate time in bed.

41 young adults with T1D who wore the continuous glucose monitor (CGM-(Dexcom G4) and Spectrum Plus concurrently for 7 continuous days/nights and were included in this analysis. Glucose was measured with a continuous glucose monitoring device every 5 min and activity with a non-dominant wrist-worn actigraph in 30-s epochs over 6–14 days. There was substantial glucose and unstructured physical activity coupling during sleep and wake, along with circadian variation based on the wavelet coherence analysis. The fluctuations in coherence between blood glucose in the shorter-duration bands were characterized by changes in blood glucose followed by changes in activity. It is also observed that those with T1D are at an elevated risk of nocturnal hypoglycemia following an evening or late afternoon session of structured activity of high intensity or long duration.

The findings highlight that both circadian rhythmicity and sleep play a role in the 24-h variation of glucoregulation. The 24-h variation in glucoregulation is intrinsically affected by the time of day independent of the sleep or wake condition (circadian) and intrinsically affected by the sleep condition irrespective of the time of day (sleep state). Thus, circadian rhythmicity and sleep are important physiological regulators of glucose, even in those with an absent autoregulation.