EEG brain networks modulation during sleep onset: the effects of aging.

The aim of the present study is to investigate differences in brain networks modulation during the pre- and post-sleep onset period, both within and between two groups of young and older individuals. Thirty-six healthy elderly and 40 young subjects participated. EEG signals were recorded during pre- and post-sleep onset periods and functional connectivity analysis, specifically focusing on the small world (SW) index, applied to EEG data (i.e., frequency bands) was examined. Significant differences in SW values were found between the pre-sleep and post-sleep onset phases in both young and older groups, with a reduction in the SW index in the theta band common to both groups. Additionally, an increase in the SW index in the beta band was exclusive to the elderly group during the post-sleep onset period, while an increase in the sigma band was exclusive to the young group. Furthermore, differences between the young and elderly groups were found during both phases, including a decrease in the SW index within the delta band, an increment in the sigma and beta bands in the elderly compared to the young group during the pre-sleep onset period, and a notable absence of sigma band modulation in the elderly group during the post-sleep onset condition. These findings provide insights into age-related changes in sleep-related brain network dynamics and their potential impact on sleep quality and cognitive functions, prompting interventions aimed at supporting healthy aging and addressing age-related cognitive decline.