The sleep paradox: The effect of weekend catch-up sleep on homeostasis and circadian misalignment

Weekend catch-up sleep involves not only changes in sleep duration between weekdays and weekends but also changes in sleep timing. When people sleep less during the weekdays, they accumulate sleep debt and extend their sleep duration on weekends to compensate, which is related with the homeostatic process. Thus, extend their sleep duration on weekends seems to be a protectively strategy of daytime function, mental and physical health. However, not all studies support this protective effect. Sleep duration changes with sleep timing. The difference in sleep timing between weekdays and weekends might bring social jet lag (SJL). Sleep duration changes with sleep timing. The difference in sleep timing between weekdays and weekends can lead to SJL, representing the discrepancy between the biological clock and the social clock. This makes SJL an indicator of circadian misalignment, which is associated with poor daytime function, reduced nighttime sleep quality, and an increased risk of depression, metabolic disturbances, and other diseases. Paradoxically, the protective effect of weekend catch-up sleep duration on the homeostatic process (compensating for sleep debt) and the potential impact of weekend catch-up sleep timing on the circadian process (circadian misalignment) contradict each other. A more comprehensive understanding of weekend catch-up sleep is essential to investigate its mechanisms using the two-process model and other influencing factors.