Reference: Haraszti, R. Á., Ella, K., Gyöngyösi, N., Roenneberg, T., & Káldi, K. (2014). Social jetlag negatively correlates with academic performance in undergraduates. Chronobiology International, 31(5), 603–612.
Ever stay up late on a weekend, to either go out and have fun or just because you can?
Although you may be able to sleep-in the next day, you’ve shifted your body’s schedule by a few hours like you would if you had traveled over several time zones. This might not be a problem for you Saturday or Sunday morning, but you might struggle with energy and concentration when you’re trying to get back into a regular schedule on Monday. When people have different sleep schedules on weekdays versus weekends, this is known as social jetlag.
Social jetlag is the result of an imbalance between two sleep systems
There are two processes that help determine when we sleep: sleep pressure (also known as the homeostatic drive for sleep) and our circadian rhythm (Borbely, 1982). These two processes can work together, or in opposition, to help promote sleep.
During wakefulness, our body has an increasing need for sleep, known as sleep pressure, which decreases when we sleep (Allada et al., 2017). When someone foregoes sleep to pull an all-nighter, their sleep pressure continues to build. Sleep pressure may reflect the build-up of a molecule called adenosine, which is a byproduct of metabolic processes (Allada et al., 2017). When we sleep, our body can flush out this adenosine build-up.
Fun fact: Caffeine prevents adenosine from binding with the sleepy centers of the brain, which is why people may experience difficulties falling asleep after consuming coffee or tea!
However, sleep pressure is not the only thing that determines sleep. The circadian rhythm (circa meaning “around”; diem meaning “day”) is your body’s 24-hour clock. The circadian rhythm controls when certain hormones are released, and when different bodily processes occur (Schwartz & Klerman, 2017). Your personal circadian rhythm has a particular preference for when you sleep, which is why some people are “night owls”, whereas other people are “early birds” or “morning larks” (Schwartz & Klerman, 2017). These sleep preferences are known as chronotypes.
Usually, the circadian rhythm and sleep pressure are in sync, and sleep occurs when there is a low circadian drive for wakefulness and high sleep pressure (see the first figure below). However, dramatic changes to when we go to bed or wake up can confuse the brain and body. Instead of the circadian rhythm and sleep pressure working together, they can become misaligned resulting in difficulties falling or staying asleep (see the second figure below).
Sleep is important for academic performance
Sleep gives our body the chance to rest and recharge. Sleep allows for our body to rebuild and store up molecules (such as glucose) that help us function the next day (Frank & Heller, 2018). It also clears up space in our brain to create room for new memories and help with learning (Walker, 2009). (See my previous article about sleep and memory).
Generally, university students with poor sleep schedules are not reaping the benefits that sleep provides to the brain and body. As a result, university students with poor sleep tend to have lower academic performance (Gilbert & Weaver, 2010; Gomes et al., 2011; Wang et al., 2016). Many also experience negative mental health impacts such as increased stress and (Lund et al., 2010; Norbury & Evans, 2019), which can further worsen their sleep.
Social jetlag and academic performance in university students
We know sleep is important to academic performance, and that social jetlag can disrupt sleep. So how does social jetlag relate to academic performance? Researchers from Semmelweis University in Budapest, Hungary, aimed to examine if the amount of social jetlag impacts academic performance (Haraszti et al., 2014). This study consisted of 780 undergraduate students who were taking the same physiology course.
Students completed a survey that collected sleep data. This survey asked questions about when the students went to bed, what time they fell asleep, and what time they woke up and got out of bed. They were asked this about their workdays and their free days (e.g., weekends) separately. They then calculated their mid-sleep points using the following equation:
For example, let’s say someone fell asleep at 1 a.m. and slept for 8 hours. Their mid-sleep time would be 5:00 a.m. [ 1+(8 ÷ 2) = 5].
Social jetlag was calculated by subtracting the mid-sleep time on free days from the mid-sleep time on workdays. Academic performance was measured by their overall course and final exam grades in the physiology course.
What did they find? Social jetlag is associated with poorer academic performance!
On average, university students experienced ~1.5 hours of social jetlag on weekends. Social jetlag was negatively associated with weekly academic performance, where greater differences in midsleep time between workdays and weekends were associated with greater decreases in academic performance (see the left panel labeled “A” in the figure below).
However, social jetlag was not associated with final exam grades (see the right panel labeled “B” in the figure below), presumably because during the exam period students have greater flexibility over their schedules and did not need to attend early morning lectures.
Finally, they found that students who would be considered “night owls” were over twice as likely to perform poorly on morning tests (see figure below).
What does this mean for you?
If you’re a student who likes to stay out late on weekends, we have bad news for you: this may be negatively impacting your academic performance. Sticking to a regular sleep schedule, although less fun, may be better for your grades. Additionally, if you’re a night owl, be mindful when scheduling your courses; having more courses in the afternoon might be better for your academic performance.
Allada, R., Cirelli, C., & Sehgal, A. (2017). Molecular mechanisms of sleep homeostasis in flies and mammals. Cold Spring Harbor Perspectives in Biology, 9(8), a027730.
Borbely, A. A. (1982). A two process model of sleep regulation. Human Neurobiology, 1(3), 195–204.
Frank, M. G., & Heller, H. C. (2018). The Function(s) of Sleep. In H. P. Landolt & J. Dijk D. (Eds.), Handbook of Experimental Pharmacology (Vol. 253, pp. 3–34). Springer, Cham.
Gilbert, S. P., & Weaver, C. C. (2010). Sleep quality and academic performance in university students: A wake-up call for college psychologists. Journal of College Student Psychotherapy, 24(4), 295–306.
Gomes, A. A., Tavares, J., & De Azevedo, M. H. P. (2011). Sleep and academic performance in undergraduates: A multi-measure, multi-predictor approach. Chronobiology International, 28(9), 786–801.
Haraszti, R. Á., Ella, K., Gyöngyösi, N., Roenneberg, T., & Káldi, K. (2014). Social jetlag negatively correlates with academic performance in undergraduates. Chronobiology International.
Lund, H. G., Reider, B. D., Whiting, A. B., & Prichard, J. R. (2010). Sleep patterns and predictors of disturbed sleep in a large population of college students. Journal of Adolescent Health, 46(2), 124–132.
Norbury, R., & Evans, S. (2019). Time to think: Subjective sleep quality, trait anxiety and university start time. Psychiatry Research, 271, 214–219.
Schwartz, W., & Klerman, E. (2017). Circadian neurobiology and the physiological regulation of sleep and wakefulness. Physiology & Behavior, 176(12), 139–148.
Walker, M. P. (2009). The role of slow wave sleep in memory processing. Journal of Clinical Sleep Medicine, 5(2 SUPPL.).
Wang, L., Qin, P., Zhao, Y., Duan, S., Zhang, Q., Liu, Y., Hu, Y., & Sun, J. (2016). Prevalence and risk factors of poor sleep quality among Inner Mongolia Medical University students: A cross-sectional survey. Psychiatry Research, 244, 243–248.