Observational study:

The goal of this observational study is to learn about the association between slow wave activity before awakening and post-awakening psychomotor vigilance task in time-fixed, 2-hour, simulated night naps in healthy individuals.

The main question aims to answer is:

Is the quantity of slow wave activity immediately before awakening associated with post-awakening psychomotor vigilance task metrics when awakened after 2-hour nap at night?

Sleepiness and fatigue are common complaints among shift workers, especially night shift workers. Napping interventions before a work shift have been reported to increase alertness and reduce accidents. However, naps may also result in impaired cognition for a brief period immediately after awakening, known as "sleep inertia", which can be particularly problematic in on-call settings and may require a worker to delay the return to work for up to about 30 minutes after waking. Although, nap duration less than 30 minutes, theoretically, may produce less intense sleep inertia. However, evidence regarding nap duration aiming to mitigate sleepiness and fatigue is mixing. We thus aimed to investigate the association between slow wave activity (SWA) assessed by EEG power spectral analysis during the last 10 minutes before awakening and 10-minute psychomotor vigilance test (PVT) immediately after awakening and 30 minutes after awakening in healthy participants on simulated night shift scenarios.

Inclusion Criteria:

1. Age between 18 and 60 years
2. History of appropriate sleep duration at least 6 hours/night for a minimum of 2 weeks assessed by sleep diary before the trial

Exclusion Criteria:

1. STOP-BANG ≥3 or previous diagnosis of obstructive sleep apnea
2. Presence of restless legs syndrome as assessed with IRLSSG criteria
3. Presence of depression as assessed by HADS (Exclude participants with HADS-Depression sub-scale score ≥8 (possible depression)
4. History of irregular work hours or shift work within 2 weeks
5. Use of sedative/hypnotic medications on a regular-basis (3 days/week or above)
6. History of epilepsy and brain tumor

Healthy volunteers aged between 18 and 60 years, without significant sleep deprivation