Deadline and exam times are linked with how long students sleep. In a Journal of Educational Psychology study of 636 first-year university students, published 15 October 2026, morning exams were linked with 61 to 82 minutes less sleep the night before than afternoon or evening exams, and afternoon exams with course grades 5 to 6 percentage points higher.
Key takeaways
- A 2026 Journal of Educational Psychology study (Ong, Chee and colleagues, National University of Singapore) tracked the sleep of 636 first-year students with a wearable across 16,677 assignment deadlines and 1,371 exams in their first semester.
- 44% of assignments were handed in within 24 hours of their deadline, and deadlines earlier in the day were linked with 11 to 49 minutes less sleep the night before.
- Morning exams were linked with 61 to 82 minutes less sleep than afternoon or evening exams; afternoon exams were linked with course grades 5 to 6 percentage points higher.
- Each hour of sleep lost below a student’s usual amount the night before an exam was linked with marks 1.2 to 3 percentage points lower.
- The one change: set your own deadline for the afternoon of the day before anything is due, so the work does not eat into your sleep window. The study did not test this step; it is a practical way to act on what it found.
What did the 2026 deadline study find?
When a deadline or exam fell early in the day, students slept less the night before, felt worse about their sleep and, for exams, earned lower grades. It is an association from real semesters, not a controlled experiment.
The team, led by Ju Lynn Ong and Michael Chee at the National University of Singapore, followed 636 first-year undergraduates through their first semester. A wearable measured sleep every night, and short smartphone check-ins asked about stress, mood and sleep satisfaction each day. The researchers then matched each night to the timing of 16,677 assignment deadlines and 1,371 exams.
| Timing | Linked with |
|---|---|
| Assignment due earlier in the day | 11 to 49 minutes less sleep than a typical night |
| Early-morning assignment deadline | the highest stress and sadness levels |
| Morning exam (vs afternoon or evening) | 61 to 82 minutes less sleep the night before |
| Morning or evening exam (vs afternoon) | course grades 5 to 6 percentage points lower |
| Each hour of sleep below usual before an exam | marks 1.2 to 3 percentage points lower |
Why do early deadlines cost sleep?
Mostly because work happens at the last minute. Nearly half of all assignments (44%) were submitted within 24 hours of the deadline, so a morning due time pushes the final push into the hours that would normally be sleep.
Students also tend to sleep late. In an earlier paper on the same NUS freshman cohort (Soon and colleagues, Sleep, 2025), 638 students wearing an Oura ring had an average bedtime of 1:53 AM, and when they gained sleep during the semester it came from waking later, not from going to bed earlier. On days with an 8 AM class, students woke after class had started on 42.6% of days before midterms and 52.4% after. A morning deadline or exam leaves little room in that pattern: bedtime rarely moves earlier, so wake time is what gets cut.
Why might afternoon exams go better?
Afternoon and evening exams came after more sleep than morning ones, and afternoon exams were linked with the best grades.
Evening exams came after more sleep than morning ones but were still linked with lower grades than afternoon ones, which hints that something beyond sleep may play a part, though the study does not show why. Earlier work agrees. In a 2015 Journal of Biological Rhythms study of 4,743 exam marks from 741 students at a Dutch secondary school (van der Vinne and colleagues, University of Groningen), students with the latest body clocks and the least sleep scored almost half a point lower, and late types did worse on exams early in the morning. The authors suggested holding exams only at the end of the morning.
Does one night of sleep before an exam really matter?
In the 2026 study it did: each hour of sleep below a student’s usual amount the night before an exam was linked with marks 1.2 to 3 percentage points lower, whatever time the exam began.
The longer run matters too. In a 2019 npj Science of Learning study of 88 MIT chemistry students wearing Fitbits (Okano, Gabrieli, Grossman and colleagues), sleep quality, length and consistency accounted for nearly 25% of the differences in grades; sleep in the month and the week before a test was linked with better grades, while the single night before a test showed no clear link. Put together, steady sleep across the term and a protected night before the exam both count. Adults, students included, are advised to sleep 7 or more hours a night on a regular basis (American Academy of Sleep Medicine and Sleep Research Society, 2015).
What are the limits of the study?
It shows links, not causes. Students who leave work late or who are given morning exams may differ in ways the study could not fully separate, and it took place at one university in Singapore.
Still, the sample is large, sleep was measured by a device rather than memory, and deadline nights were compared with each student’s own typical night.
What is the one change to make?
Set your own deadline for the afternoon of the day before anything is due, and hold to it as the real one. The study did not test personal deadlines, but work that is finished by late afternoon cannot spill into your sleep window, whatever time the official deadline is.
- Put every due date on the plan, then add a personal deadline at 4 PM the day before.
- Block focused work time in the days ahead so the personal deadline is realistic.
- Keep your usual bedtime and wake time the night before a deadline or exam; see Regular Wake Times for Midterms.
- When you can choose an exam slot or set a team deadline, pick the afternoon.
- Cut caffeine early in the afternoon so it does not push bedtime later; see Caffeine Cutoff Time.
More help for students: How to Make a Daily Schedule for College and How to Plan a Midterm Day on My BodyClock. Curious whether your body clock runs early or late? Take the Body Clock Type quiz.
Your day on My BodyClock
The day above on My BodyClock shows a student’s day with an assignment due the next morning. Sleep runs from 11:30 PM to 7:30 AM, a daylight walk and breakfast start the day, and the assignment is finished and submitted by a personal 4 PM deadline. A run, dinner with friends and a short evening review follow, then music and a wind-down with a book, so the night before the deadline is an ordinary night of sleep.
Build your own week with personal deadlines and a fixed sleep window in Owaves: My BodyClock on the App Store, or join the Android waitlist.
FAQ
Do morning exams affect sleep?
They are linked with less of it. In a 2026 study of 636 first-year students wearing sleep trackers, students slept 61 to 82 minutes less before morning exams than before afternoon or evening exams. The study is observational, so it shows a link, not proof of cause.
What time of day is best for an exam?
In the 2026 study, exams that started in the afternoon were linked with course grades 5 to 6 percentage points higher than morning or evening exams. A 2015 Dutch school study also found late-sleeping students scored lower on early-morning exams.
Is an 11:59 PM deadline bad for sleep?
The 2026 study did not single out 11:59 PM deadlines, but it found that assignments due earlier in the day were linked with 11 to 49 minutes less sleep the night before than a typical night, since 44% of work was handed in within 24 hours of the deadline. What matters most is not finishing in the hours you would normally sleep.
Does sleep the night before an exam matter?
In the 2026 study, each hour of sleep below a student’s usual amount the night before an exam was linked with marks 1.2 to 3 percentage points lower. A 2019 MIT study linked sleep over the month and week before a test, not the single night, with grades, so together they point to steady sleep.
If you’re in crisis in the US, call or text 988 (Suicide & Crisis Lifeline). Outside the US, contact local emergency services.
Sources
- Ong JL, Lepcha Y, Chua XY, Soon CS, Qin S, Massar SAA, Chee MWL. Timing of assignment deadlines and examinations relates to sleep, well-being, and academic performance. Journal of Educational Psychology, published online 15 October 2026. doi:10.1037/edu0001099. https://doi.org/10.1037/edu0001099
- Soon CS, Chua XY, Leong RLF, Ong JL, Massar SAA, Qin S, Chong KHM, Onnela JP, Chee MWL. A longitudinal study of sleep in university freshmen: facilitating and impeding factors. Sleep, 2025;48(10):zsaf156. doi:10.1093/sleep/zsaf156. https://pmc.ncbi.nlm.nih.gov/articles/PMC12515602/
- Okano K, Kaczmarzyk JR, Dave N, Gabrieli JDE, Grossman JC. Sleep quality, duration, and consistency are associated with better academic performance in college students. npj Science of Learning, 1 October 2019;4:16. doi:10.1038/s41539-019-0055-z. https://pmc.ncbi.nlm.nih.gov/articles/PMC6773696/
- University of Groningen. Later to school, better grades (on van der Vinne V, et al., Timing of examinations affects school performance differently in early and late chronotypes, Journal of Biological Rhythms, 2015;30(1):53-60, doi:10.1177/0748730414564786). 22 December 2014. https://www.rug.nl/news/2014/12/later-naar-school-betere-cijfers?lang=en
- Watson NF, Badr MS, Belenky G, et al. Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the American Academy of Sleep Medicine and Sleep Research Society. Sleep, 2015;38(6):843-844. doi:10.5665/sleep.4716. https://pmc.ncbi.nlm.nih.gov/articles/PMC4434546/
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