Sleep Duration and Subsequent Cortical Thinning in Cognitively Normal Older Adults

Abstract

Study objectives: To determine the association between self-reported sleep duration and cortical thinning among older adults.

Methods: We studied 122 cognitively normal participants in the Baltimore Longitudinal Study of Aging with a mean age = 66.6 y (range, 51-84) at baseline sleep assessment and 69.5 y (range, 56-86) at initial magnetic resonance imaging (MRI) scan. Participants reported average sleep duration and completed a mean of 7.6 1.5-T MRI scans (range, 3-11), with mean follow-up from initial scan of 8.0 y (range, 2.0-11.8).

Results: In analyses adjusted for age, sex, education, race, and interval between sleep assessment and initial MRI scan, participants reporting > 7 h sleep at baseline had thinner cortex in the inferior occipital gyrus and sulcus of the left hemisphere at initial MRI scan than those reporting 7 h (cluster P < 0.05). In adjusted longitudinal analyses, compared to those reporting 7 h of sleep, participants reporting < 7 h exhibited higher rates of subsequent thinning in the superior temporal sulcus and gyrus, inferior and middle frontal gyrus, and superior frontal sulcus of the left hemisphere, and in the superior frontal gyrus of the right hemisphere; those reporting > 7 h of sleep had higher rates of thinning in the superior frontal and middle frontal gyrus of the left hemisphere (cluster P < 0.05 for all). In sensitivity analyses, adjustment for apolipoprotein E (APOE) e4 genotype reduced or eliminated some effects but revealed others. When reports of < 7 h of sleep were compared to reports of 7 or 8 h combined, there were no significant associations with cortical thinning.

Conclusions: Among cognitively normal older adults, sleep durations of < 7 h and > 7 h may increase the rate of subsequent frontotemporal gray matter atrophy. Additional studies, including those that use objective sleep measures and investigate mechanisms linking sleep duration to gray matter loss, are needed.

Keywords: aging; atrophy; cortical thinning; gray matter; neuroimaging; sleep duration.

Figure 1

Prospective association of sleep duration with subsequent cortical thinning in cognitively normal older adults. Longitudinal magnetic resonance images (MRIs) from 122 cognitively normal participants indicate faster rates of cortical thinning in frontal and temporal regions among those reporting < 7 h average sleep duration (n = 24) and those reporting > 7 h average sleep duration (n = 50), compared to those reporting 7 h of sleep duration (n = 48) over the prior month. Fixed effects included age, sex, time, interval between sleep assessment and initial MRI scan, education, race, sleep, education × time, race × time, age × time, sex × time, and sleep × time; subject-specific slopes and intercepts were random effects. A primary (vertex-level) threshold of P < 0.01 was applied; figure displays regions with a cluster P < 0.05.