Multi‐Night Electroencephalography Reveals Positive Association Between Sleep Efficiency and Hippocampal Subfield and Entorhinal Cortex Volumes in Healthy Aging

ABSTRACT Age‐related atrophy of the human hippocampus and the enthorinal cortex starts accelerating at around age 60. Due to the contributions of these regions to many cognitive functions seamlessly used in everyday life, this can heavily impact the lives of elderly people. The hippocampus is not a unitary structure, and mechanisms of its age‐related decline appear to differentially affect its subfields. Human and animal studies have suggested that altered sleep is associated with hippocampal atrophy. Yet, we know little about subfield specific effects of altered sleep in healthy aging and their effect on cognition. Here, in a sample of 118 older middle‐aged and older adults (Mage = 63.25 y, range: 50–80 y), we examined the association between highly reliable hippocampal subfield and entorhinal cortex volumetry (n = 112), sleep measures derived from multi‐night recordings of portable electroencephalography (n = 61) and episodic memory (n = 117). Objective sleep efficiency—but not self‐report measures of sleep—was associated with entorhinal cortex volume when controlling for age. Age‐related differences in subfield volumes were associated with objective sleep efficiency, but not with self‐report measures of sleep. Moreover, participants characterized by a common multivariate pattern of subfield volumes that contributed to positive sleep–subfield volume associations, showed lower rates of forgetting. Our results showcase the benefit of objective sleep measures in identifying potential contributors of age‐related differences in brain‐behavior couplings. In a sample of 118 fifty to 80‐year‐old healthy adults, multi‐night recordings of portable electroencephalography (EEG) revealed associations between hippocampal subfield and entorhinal cortex volumes and sleep that were otherwise not detected by subjective sleep measures. Moreover, multivariate correlational analysis techniques suggest that these associations manifest in episodic memory performance.