Neurobehavioral Outcomes Immediately Following a Daytime Sleep Opportunity With Pink Noise

Introduction: Pink noise is purported to enhance slow wave activity during sleep. Increased slow wave activity during a sleep episode has been associated with greater sleep inertia symptoms after waking. We investigated whether a pink noise intervention during a 4-hour daytime nap affected neurobehavioral outcomes immediately after the sleep opportunity.

Methods: Fourteen participants (7 female, 7 male; MAge = 24.86 y, SD = 5.20) spent two 26-hour periods in the sleep laboratory, both preceded by a week at home of 8.5 hours’ time-in-bed (verified by actigraphy). Both lab visits included a 4-hour nap opportunity ending 10 hours after habitual waketime on the first day (i.e., during the circadian day). In a randomized, cross-over design, the nap either involved pink noise (50 dB) played through headband speakers (intervention), or a headband with no sound playing (control). A test battery including the Karolinska Sleepiness Scale (KSS) and a 5-minute psychomotor vigilance task (PVT; NASA PVT+ App) was administered before lights out and again at 2, 12, 22, and 32 minutes after lights on. Participants were seated at a desk adjacent to their bed during testing. Mixed effects models were used to investigate the difference between the two conditions and across test bouts. Sex and baseline measures were included as covariates.

Results: There was no difference in sleep inertia outcomes between conditions. There was a significant effect of test bout for KSS with the greatest sleepiness experienced 2 minutes after the end of the nap opportunity (p = .004) There were no other significant main or interaction effects for KSS, PVT speed, or PVT lapses (all p > .05).

Discussion: These preliminary findings suggest that there was no difference in subjective alertness nor objective vigilant attention in the 40 minutes following a daytime nap opportunity with pink noise compared to a no-noise control. Future analyses are needed to investigate how sleep metrics may have influenced these results.