As in previous studies [33 (link),42 (link)], sleep was objectively assessed with a one-channel, portable sleep-EEG recording device (Fp2-A1; electromyogram; electrooculogram; Somnowatch®; Somnomedics; Randersacker, Germany). These simple though powerful devices have been shown to provide reliable data [36 (link)]; two experienced sleep lab experts visually analyzed the EEG signals according to standard procedures [45 (link)]. Sleep continuity parameters consisted of: (a) sleep onset latency (min); (b) total sleep time (min); and (c) duration of awakenings after sleep onset (min). Sleep architecture parameters were: (a) non-rapid eye movement sleep (non-REM sleep); (b) light sleep (stages 1 and 2): absolute (min) and relative duration (%); (c) slow wave sleep/deep sleep (stages 3 and 4): absolute (min) and relative duration (%); and (d) rapid eye movement sleep (REM): absolute (min) and relative duration (%). All measurements were reported in means (M) and standard deviations (SD).
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