Physiologically, adolescents and young adults tend to have a delayed circadian preference and are “night owls.”This change occurs in association with puberty; more physically mature adolescents prefer later bedtimes and may have a lower homeostatic sleep drive, and consequently, are less sleepy at night. The typical adult circadian period is 24.1 hours, compared to an adolescent’s circadian period of 24.27 hours; this longer period makes it easier for bedtime to shift later. A cardinal sign of a delayed circadian system is an irregular sleep schedule, where students have catch-up sleep on the weekend. High school and college students demonstrate a 1–3 hour sleep deficit on school nights, with a much longer sleep duration and often a later wake time on the weekends.
How the circadian rhythm and homeostatic sleep drive change with puberty are not well understood. Still, the cumulative effect is that adolescents and young adults feel more awake in the evening, have difficulty falling asleep until later, and consequently, have an insufficient sleep during the school week and catch up on sleep on the weekend.
Exactly when this nocturnal preference or “night owl” tendency diminishes remains unclear. When evaluated longitudinally, weekday bedtimes continued to delay until around 19 years of age, with weekend bedtimes remaining later until the early 20s. However, other studies have shown this delay persisting until junior year. The transition from high school to college also impacts college students go to bed 75 minutes later than high school students. In this study, freshman students’ bedtime was 12.22 am and 1.58 am, with a rise time of 8.08 am, and 10.26 am on weekdays and the weekend, respectively.
Sleepiness and irregular sleep schedules have many unintended consequences, one of which negatively impacts learning, memory, and performance. The precise details of the relationship between sleep and memory formation are not yet completely understood. The dual-process theory maintains that certain types of memory are dependent on specific sleep states, such that procedural memory (knowing how) may be dependent on REM (rapid eye movement) sleep and declarative memory (knowing what) on NREM (non-REM) sleep. The sequential processing theory suggests that memories require an orderly succession of sleep stages, i.e., memory formation may be prompted by slow-wave sleep and consolidated by REM sleep.
Both theories may help to explain how a student’s sleep pattern could impact learning. In one study, REM sleep deprivation eliminated sleep-induced improvement on a visual perceptual learning (procedural) task; the same effect was not found with selective slow-wave sleep deprivation.REM sleep normally occurs every 90–120 minutes, approximately 4–5 times in a typical night, with each REM sleep period growing progressively longer, with the last episode near rising time. Therefore, college students with early morning classes may not attain the last 1–2 REM sleep periods, thus adversely affecting procedural memory. However, other studies suggest that NREM rather than REM sleep enhances procedural memories, while other studies correlated improvement with slow-wave sleep followed by REM sleep. These theories support that sleep deprivation may limit the amount of REM sleep and/or slow-wave sleep that students obtain, which may compromise both learning and memory, but further research is required to clarify this.
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