Differential impact of chronotype on weekday and weekend sleep timing and duration

Abstract

Most recommendations are that adults should obtain 7-8 hours of sleep per night, although there are individual differences in self-reported sleep need. Chronotype (preference for early or late sleep timing), in combination with social demands, may affect the ability to obtain adequate sleep. This questionnaire study assessed perceived sleep need and self-reported sleep timing and duration during the week and on the weekend with respect to chronotype in visitors to the Museum of Science in Boston. Increasing age was associated with greater morningness. After adjusting for age, we found no significant association between chronotype and self-reported sleep need, or between chronotype and weekday sleep duration. However, we did find that greater eveningness was associated with a larger gap between self-reported sleep need and weekday sleep duration. On weekends, greater eveningness was associated with a longer sleep duration and greater extension of sleep, with the sleep extension achieved by later wake times. Together, these findings suggest that evening types accumulate a sleep debt during the week, despite reporting a similar sleep need and duration as morning types, and evening types then attempt to make up for that lost weekday sleep on the weekends. Studies of sleep need and sleep duration should take chronotype into account, and studies of chronotype may be confounded by the association between age and morningness, and must account for this potential confound in selection criteria and/or analysis.

Figure 1

Relationship between MEQ score and delay of waketime on weekends. The delay of waketime (in hours) between weekdays and weekends for each of the 145 participants is plotted with respect to their MEQ score. MEQ scores can range from 18 to 86, with higher numbers indicating greater morningness. Positive wake time delays indicate later weekend than weekday waketimes, while negative delays indicate earlier weekend than weekday waketimes. Abbreviation: MEQ, Morningness–Eveningness Questionnaire.

Figure 2

Relationship between MEQ score and weekend sleep duration. The weekend sleep duration (in hours) calculated from self-reported weekend bedtimes and waketimes for each of the 145 participants is plotted with respect to their MEQ score. MEQ scores can range from 18 to 86, with higher numbers indicating greater morningness. Abbreviation: MEQ, Morningness–Eveningness Questionnaire.

Figure 3

Relationship between MEQ score and weekend sleep extension. The extension of sleep (in hours) between weekdays and weekends calculated from self- reported weekday and weekend bed and wake for each of the 145 participants is plotted with respect to their MEQ score. MEQ scores can range from 18 to 86, with higher numbers indicating greater morningness. Positive weekend sleep extensions indicate longer weekend than weekday sleep, while negative extensions indicate shorter weekend than weekday sleep. Abbreviation: MEQ, Morningness–Eveningness Questionnaire.

Figure 4

Relationship between MEQ score and age. The age (in years) for each of the 145 participants is plotted with respect to their MEQ score. MEQ scores can range from 18 to 86, with higher numbers indicating greater morningness. There was a significant association between age and MEQ score when evaluated with a mixed model (see text) and there was a significant correlation (Pearson correlation coefficient r = 0.33, P < 0.0001). Abbreviation: MEQ, Morningness–Eveningness Questionnaire.