0080 Poor Sleep Hygiene in Adolescence is Associated with Disrupted Encoding and Consolidation of Newly Learned Words

Abstract Introduction Sleep before learning restores hippocampal encoding capacity (Cirelli & Tononi, 2020), while sleep after learning stabilises and integrates new memories into long-term neocortical stores (Klinzing et al., 2019). Both functions of sleep are known to facilitate word learning in adults and young children (Davis & Gaskell, 2009; March et al., 2023). Yet, little is known about these mechanisms in adolescence, despite adolescence being a developmental period marked by considerable disruption to sleep. These disruptions include shifts in circadian rhythms that delay sleep timing, alongside behavioural factors like increased device use before bed. Together, these changes lead to chronic sleep restriction (Gradisar et al., 2011). We therefore hypothesised that the transition from pre-adolescence to adolescence would lead to poorer sleep and worse encoding and consolidation of new words. Methods Participants (225 11-12-year-olds and 263 13-15-year-olds) completed a word learning task across two sessions spaced 24 hours apart, testing immediate encoding and overnight consolidation. Sleep was assessed via self-report questionnaires as well as a 2-week sleep diary prior to testing. Objective measures of sleep were derived from actigraphy in a subsample of participants. Results Bayesian mixed effects models revealed substantial differences between age groups. Older adolescents exhibited stronger evening chronotypes, later sleep onset (41 mins later), shorter duration (44 mins shorter), and poorer sleep hygiene (habits and environmental factors that impact sleep). In the word leaning task, older adolescents outperformed younger peers at encoding, but underperformed at delayed recall, suggesting age-related improvements in encoding were offset by weaker overnight consolidation. Across groups, better sleep hygiene predicted better encoding and consolidation (βs = 0.10 - 0.56). Closer analysis of sleep hygiene suggested physical activity before bedtime and lack of bedtime routine were particularly strongly associated with poorer memory. Conclusion These findings suggest that poor behavioural choices around bedtime contribute to the trade-off between improved encoding capacity and reduced consolidation efficiency in the transition from pre-adolescence to adolescence. This supports theories of word learning that assign a key role for sleep and suggest that interventions targeting modifiable sleep behaviours could strengthen memory formation during this developmental period. Support (if any)