The regional EEG pattern of the sleep onset process in older adults

Healthy aging is characterized by macrostructural sleep changes and alterations of regionalelectroencephalographic (EEG) sleep features. However, the spatiotemporal EEG pattern of thewake-sleep transition has never been described in the elderly. The present study aimed to assessthe topographical and temporal features of the EEG during the sleep onset (SO) in a group of36 older participants (59–81 years). The topography of the 1 Hz bins’ EEG power and the timecourse of the EEG frequency bands were assessed. Moreover, we compared the delta activity anddelta/beta ratio between the older participants and a group of young adults. The results pointto several peculiarities in the elderly: (a) the generalized post-SO power increase in the slowestfrequencies did not include the 7 Hz bin; (b) the alpha power revealed a frequency-specific pattern ofpost-SO modifications; (c) the sigma activity exhibited only a slight post-SO increase, and its highestbins showed a frontotemporal power decrease. Older adults showed a generalized reduction of deltapower and delta/beta ratio in both pre- and post-SO intervals compared to young adults. From aclinical standpoint, the regional EEG activity may represent a target for brain stimulation techniquesto reduce SO latency and sleep fragmentation.