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Objectives: To examine the association between sleep duration trajectories over 28 years and measures of cognition, grey matter volume and white matter microstructure. We hypothesize that consistently meeting sleep guidelines that recommend at least seven hours sleep per night will be associated with better cognition, greater grey matter volumes, higher fractional anisotropy and lower radial diffusivity values. Methods: We studied 613 participants (age 42.3 ± 5.03 years at baseline) who self-reported sleep duration at five timepoints between 1985 and 2013, and who had cognitive testing and magnetic resonance imaging administered at a single timepoint between 2012 and 2016. We applied latent class growth analysis to estimate membership into trajectory groups based on self-reported sleep duration over time. Analysis of grey matter volumes was carried out using FSL Voxel-Based- Morphometry and white matter microstructure using Tract Based Spatial Statistics. We assessed group differences in cognitive and MRI outcomes using non-parametric permutation testing. Results: Latent class growth analysis identified four trajectory groups, with an average sleep duration of 5.4 ± 0.2 hours (5%, N=29), 6.2 ± 0.3 hours (37%, N=228), 7.0 ± 0.2 hours (45%, N=278) and 7.9 ± 0.3 hours (13%, N=78). No differences in cognition, grey matter and white matter measures were detected between groups. Conclusions: Our null findings suggest that current sleep guidelines that recommend at least seven hours sleep per night may not be supported in relation to an association between sleep patterns and cognitive function or brain structure.


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