Sleepiness, sleep duration, and human social activity: An investigation into bidirectionality using longitudinal time-use data

• Published in: Proceedings of the National Academy of Sciences - PNAS 2020-09, Vol.117 (35), p.21209-21217
• Main Authors: Holding, Benjamin C., Sundelin, Tina, Schiller, Helena, Åkerstedt, Torbjörn, Kecklund, Göran, Axelsson, John
• Format: Article
• Language: English
• Subjects: Adult; Biological Sciences; Circadian Rhythm - physiology; Cognitive ability; Driver fatigue; Female; Humans; interpersonal relations; Investigations; Longitudinal Studies; Male; Motivation; Nonlinear analysis; Psychology; psykologi; Risk analysis; Risk factors; Sleep; Sleep - physiology; Sleep and wakefulness; Sleep deprivation; Sleep Deprivation - physiopathology; Sleep Stages - physiology; sleepiness; Social Behavior; Social Sciences; Time Factors; Time of use; time-use; Wakefulness - physiology; Work Schedule Tolerance - physiology
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.2004535117

Daytime sleepiness impairs cognitive ability, but recent evidence suggests it is also an important driver of human motivation and behavior. We aimed to investigate the relationship between sleepiness and a behavior strongly associated with better health: social activity. We additionally aimed to investigate whether a key driver of sleepiness, sleep duration, had a similar relationship with social activity. For these questions, we considered bidirectionality, time of day, and differences between workdays and days off. Over 3 wk, 641working adults logged their behavior every 30 min, completed a sleepiness scale every 3 h, and filled a sleep diary every morning (rendering >292,000 activity and >70,000 sleepiness datapoints). Using generalized additive mixed-effect models, we analyzed potential nonlinear relationships between sleepiness/sleep duration and social activity. Greater sleepiness predicted a substantial decrease in the probability of social activity (odds ratio 95% CI = 0.34 to 0.35 for days off), as well as a decreased duration of such activity when it did occur. These associations appear especially robust on days off and in the evenings. Social duration moderated the typical time-of-day pattern of sleepiness, with, for example, extended evening socializing associated with lower sleepiness. Sleep duration did not robustly predict next-day social activity. However, extensive social activity (>5 h) predicted up to 30 min shorter subsequent sleep duration. These results indicate that sleepiness is a strong predictor of voluntary decreases in social contact. It is possible that bouts of sleepiness lead to social withdrawal and loneliness, both risk factors for mental and physical ill health.