LAUSR

Studies indicate the relevance of the timing system as integrating the causes and antecedents of sleepiness. Recently, social jetlag and sleep variability have been highlighted in regard to their relevance to sleep health. While the circadian misalignment represented by those variables have a known effect on sleepiness, it is often confounded by sleep debt. Therefore, we sought to assess the association between social jetlag, sleep variability and sleepiness, with sleep debt as a mediator in a representative population-based study. A representative population-based sample of 1037 participants was analyzed. Participants answered the UNIFESP Sleep Questionnaire and Epworth Sleepiness Scale to collect data regarding sleep timing and subjective sleepiness, respectively. Subsequently, mid-sleep time, total sleep time, social jetlag (absolute difference between mid-sleep time on workdays and mid-sleep time on free days), standard deviation of mid-sleep time and sleep debt (difference between total sleep time on workdays and free days) were calculated. Generalized linear models were conducted to assess if sleep variability and social jetlag had an effect on the Epworth Sleepiness Scale score, with BMI as a control variable. A mediation model was run to test if observed significant effects were mediated by sleep debt. Average sleep variability was 0.69±0.5 hours, and prevalence rates were 23% for >1h and 12% for >2h of social jetlag. There was a statistically significant association between social jetlag and Epworth Sleepiness Scale score, independently of BMI. Moreover, this effect was significantly mediated by sleep debt. No association between sleep variability and sleepiness was observed. The significant association between social jetlag and sleepiness and its mediation by sleep debt are evidence of their role in sleep health and should be considered as relevant factors in future population-based studies analyzing sleep. Our studies are supported by grants from the Associacão Fundo de Incentivo à Pesquisa (AFIP). GLF is supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brazil (CAPES) – Finance Code 001) and CNPq (#141445/2021-1 to GLF). MLA and ST are Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) fellowship recipients.