Abstract
Study ObjectivesTo examine the association between sleep duration trajectories over 28 years and measures of cognition, gray matter volume, and white matter microstructure. We hypothesize that consistently meeting sleep guidelines that recommend at least 7 hours of sleep per night will be associated with better cognition, greater gray matter volumes, higher fractional anisotropy, and lower radial diffusivity values.MethodsWe studied 613 participants (age 42.3 ± 5.03 years at baseline) who self-reported sleep duration at five time points 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 gray 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 nonparametric permutation testing.ResultsLatent 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, gray matter, and white matter measures were detected between groups.ConclusionsOur null findings suggest that current sleep guidelines that recommend at least 7 hours of sleep per night may not be supported in relation to an association between sleep patterns and cognitive function or brain structure.
Highlights
Both short- and long-sleep durations are consistently associated with increased mortality and unfavorable health outcomes, including elevated risk of stroke, diabetes, heart disease, and psychiatric disorders [1, 2]
A small number of longitudinal studies have indicated that an adverse change in sleep duration over time is associated with impaired cognitive performance [6,7,8]
In order to understand the mechanisms that underlie associations between sleep and cognition, a number of studies have used magnetic resonance imaging (MRI) techniques to examine the relationship between sleep duration and brain structure
Summary
Both short- and long-sleep durations are consistently associated with increased mortality and unfavorable health outcomes, including elevated risk of stroke, diabetes, heart disease, and psychiatric disorders [1, 2]. In order to understand the mechanisms that underlie associations between sleep and cognition, a number of studies have used magnetic resonance imaging (MRI) techniques to examine the relationship between sleep duration and brain structure. Both short- and long-sleep durations have been linked with increased rates of brain atrophy [9, 10] and markers of white matter structure [11, 12], results have been shown to vary according to the definition of short-, normal-, and long-sleep duration applied [10], and sleep duration has typically only been examined at a single time point. Assessing sleep over an extended period of time has the potential to characterize how sleep habits change with age, and to identify which trajectories are associated with adverse health outcomes
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