Sadr, Mahshid2025-05-082025-05-082025-05-08http://hdl.handle.net/10393/50424https://doi.org/10.20381/ruor-31088Background: Cognitive reserve (CR) has been associated with better cognitive performance, yet it remains unclear whether sleep behaviours, a lifestyle factor, can serve as a proxy for cognitive reserve. This study aims to identify whether sleep behaviours influence the relationship between brain structure and cognitive performance in the same way in healthy younger and older groups. Materials and Methods: This study included 81 participants: 41 in the younger group (18–30 years) and 40 in the older group (60+ years). Sleep behaviours were evaluated using self-reported questionnaires, cognitive performance was measured through a neuro-behavioural battery, and brain volume was obtained using MRI scans. Linear modelling examined the moderating effects of sleep behaviours on brain-cognitive performance relationships across age groups. Results: This study revealed age-related differences in how average sleep hours influence the relationship between brain structure and cognitive performance. Specifically, the interaction between age, sleep behaviours, and brain regions illustrates that sleep serves as a mechanism of cognitive reserve. Conclusion: Age-specific sleep behaviours influence the relationship between brain structure and cognitive performance. Personalized interventions related to sleep hygiene can enhance cognitive performance in the younger and older groups, potentially mitigating age-related cognitive decline.enCognitive ReserveSleepBrain StructureAgingMRICognitive PerformanceThesis