Effects of night-to-night variations in objectively measured sleep on blood glucose in healthy university students.

Study objectives: We examined associations between daily variations in objectively measured sleep and blood glucose in a sample of non-diabetic young adults to complement laboratory studies on how sleep affects blood glucose levels.

Methods: 119 university students underwent sleep measurement using an Oura Ring 2 and continuous glucose monitoring (CGM) for up to 14 days. In 69 individuals who consumed a standardised diet across the study, multilevel models examined associations between sleep duration, timing and efficiency and daily CGM profiles. Separately, in 58 individuals, multilevel models were used to evaluate postprandial glycaemic responses to a test meal challenge on 7 days. Participants also underwent oral glucose tolerance testing once after a night of ad libitum sleep, and again following a night of sleep restriction by 1-2 hours relative to that individual's habitual sleep duration. Between-condition glucose and insulin excursions, HOMA-IR and Matsuda index were compared.

Results: Nocturnal sleep did not significantly influence following-day CGM profiles, postprandial glucose, or nocturnal mean glucose levels (all Ps>0.05). Longer sleep durations were associated with lower same-night glucose variability (all Ps<0.001). However, the range of variation of sugar levels was small and unlikely to be of functional significance. Considering naps in the analysis did not alter the findings. Sleep restriction by an average of 1.73 hours (SD=0.97) did not significantly impact excursions in glucose or insulin or insulin sensitivity the following morning (all Ps>0.05).

Conclusions: Glucose handling in young, healthy adults may be more resilient to real-life fluctuations in sleep patterns than previously thought.