0151 Subjective sleep onset latency is influenced by the sleep structure and body heat loss in human subjects

Abstract

Abstract Introduction Humans can estimate the time that has elapsed during sleep (time estimation ability; TEA). Although research on the TEA during sleep has advanced in the field of sleep research, few studies have focused on the relationship between the subjective sleep onset latency (SOL), which is an indicator of TEA, and objective sleep structures, body heat loss, and body temperature. This paper investigates the association of the subjective SOL with sleep structures such as the objective SOL, duration of each sleep stage, subjective sleep parameters, and body heat loss in healthy young participants. Methods Twenty six participants (7 men and 19 women, mean age of 21.5 ± 0.5 years) having no sleep problems participated in a 1-hour polysomnographic recording that obtained objective sleep parameters during the daytime while temperatures of the skin (i.e., dorsum of the hand and foot, forehead, and subclavian) and eardrum were recorded at intervals of 1 min. The distal–proximal skin temperature gradient (DPG), which is a good predictor of body heat loss and sleepiness, was calculated. Subjective parameters, such as the subjective SOL, sleep time, sleep depth, sleepiness, and mood, were evaluated before and after sleep. We examined the association of the subjective SOL with objective sleep parameters, DPG, and other subjective parameters. Results Most participants estimated their sleep latency to be longer than their actual SOL (mean objective SOL of 7.6 min vs. subjective SOL of 13.7 min). The objective SOL was significantly correlated with each sleep stage parameter whereas the subjective SOL was negatively correlated with the stage N2 sleep duration (Rho = −0.454, p = 0.020) and correlated with the stage N2 sleep latency (Rho = 0.402, p = 0.051). Participants who estimated a shorter subjective SOL had a higher DPG before sleep periods than that after sleep onset (Rho = −0.692, p < 0.001). Additionally, the subjective SOL was correlated with the subjective sleep depth, subjective wake after sleep onset, and restorative sleep. Conclusion The subjective sleep onset latency in the healthy young participants was affected by the degree of body heat loss before sleep onset and stable shallow nonrapid-eye-movement sleep. Support (If Any)