Spectral EEG markers of the drives for wake and sleep in afternoon naps as the correlates of subjective and objective measures of daytime sleepiness

Despite our capability to consciously perceive sleepiness, the consensus on the method of its objective measurement is not reached. The complex nature of this transitional state between wake and sleep states might be one of explanations of the failure to validate subjective sleepiness self-assessments against objective sleepiness measures, such as spectral electroencephalographic (EEG) powers. Our previous pilot study showed that the disconnect between excessive daytime sleepiness (EDS) assessed with Epworth Sleepiness Scale (ESS) and measured as Latency to Sleep Onset (SOL) can be linked to their differential relationship with the opposing drives for sleep and wake. To try to replicate this result, we enlarged the sample of nap study from 27 to 80 university students and found again that ESS score and min of SOL were differentially linked to scores on the first and second principal components of the EEG spectrum that are the indicators of these two opposing sleep–wake regulatory processes. Thus, a stronger sleep drive and a weaker opposing wake drive might be the major contributors to the subjective and objective indicator of EDS, respectively. The results are discussed in light of findings of questionnaire studies indicating a relatively high prevalence of ESS-based EDS among university students. © The Author(s), under exclusive licence to EDP Sciences, Springer-Verlag GmbH Germany, part of Springer Nature 2026.