Longer sleep linked to lower glucose variability in healthy 18-year-olds in bidirectional pattern

Researchers at University of Copenhagen and COPSAC fitted participants with wrist actigraphs and interstitial glucose sensors for 14 days of free-living conditions. Longer total sleep time preceded lower glucose coefficient of variation and fewer excursions above 7.8 mmol/L, while lower daytime variability predicted modestly extended sleep the next night. The design captured naturalistic behavior yet could not isolate whether dietary timing, physical activity, or direct neuroendocrine effects mediated the associations.

Prior work in middle-aged cohorts, such as the 2019 Diabetes Care meta-analysis of 28 studies, established similar sleep-glucose links mainly in prediabetes, leaving adolescent data sparse. This study extends the pattern to metabolically healthy young adults and highlights a potential morning cortisol-linked glucose rise that may blunt subsequent cravings. Behavioral confounding remains plausible because late-night screen use often coincides with both delayed bedtimes and higher glycemic load snacks.

An interventional trial randomizing sleep extension versus control in this age group would be required to test causality and quantify whether a 30-minute bedtime shift produces clinically meaningful reductions in glycemic variability over six months. Public health messaging could emphasize consistent bedtimes as a low-cost lever before metabolic risk solidifies.