A study published in the Science of Learning suggests that a good night’s sleep before a test does not affect academic performance. However, the quality and duration of sleep in the month leading up to an exam does.
While much research has documented the link between sleep and academic performance, most studies have relied on self-report measures of students’ sleep quality. Study authors Kana Okano and team opted to conduct a sleep-tracking study that relied on a completely objective assessment of sleep duration and quality — a Fitbit tracker.
“By collecting quantitative sleep data over the course of the semester on nearly 100 students, we aimed to relate objective measures of sleep duration, quality, and consistency to academic performance from test to test and overall in the context of a real, large university college course,” Okano and colleagues say.
The final sample consisted of 88 college students of an average of 18 years old. All students were enrolled in the same introductory chemistry course at MIT and wore Fitbit activity trackers throughout their semester. The Fitbit devices used “a combination of the wearer’s movement and heart-rate patterns to estimate the duration and quality of sleep.” Throughout the chemistry course, students had 9 quizzes, 3 midterm exams, and one final exam. At the end of the semester, researchers calculated each student’s overall academic score based on the sum of their performances on all of these tests.
Researchers compared students’ sleep data to their overall academic scores. First, students who slept more throughout the semester and students who displayed a higher quality of sleep had higher overall academic scores. Conversely, those with greater inconsistency in sleep had lower academic scores. Moreover, sleep quality, duration, and consistency explained almost 25% of the variance in students’ overall grade performance.
“It is reported that SATs (standardized test for college admission in the US) accounts for approximately 23% of the variance in students’ academic performance in college. This contrast is striking,” study author Jeffrey C. Grossman of the Massachusetts Institute of Technology told PsyPost.
When it came to specific test grades, an interesting finding emerged. Researchers found that neither a student’s sleep duration nor sleep quality the night before a midterm or quiz had an effect on a student’s performance on that test.
“The amount of sleep the night before an exam is uncorrelated to performance; rather, it’s consistent sleep during the time when the learning is happening (the week or month before) that matter and correlates to test performance,” Grossman said.
When researchers looked at the students’ overall quality and duration of sleep in the month (and week) leading up to each test, a significant correlation between sleep measures and performance was found.
“Rather than the night before a quiz or exam,” the researchers say, “it may be more important to sleep well for the duration of the time when the topics tested were taught. The implications of these findings are that, at least in the context of an academic assessment, the role of sleep is crucial during the time the content itself is learned, and simply getting good sleep the night before may not be as helpful.”
Interestingly, female students showed better quality and more consistent sleep than male students and had overall higher academic scores than males. However, when researchers controlled for sleep quality, women’s academic advantage disappeared, suggesting that gender differences in academic performance might be completely explained by sleeping behavior.
Among limitations, researchers cannot be sure whether other mediating factors could be simultaneously affecting both sleeping behavior and academic performance — such as stress, anxiety, or personality traits. A controlled study with experimental manipulations would be needed in order to determine causality.
“Correlations do not imply causation so there is a possibility that the students who slept well just happened to be good to begin with in the subject at hand (freshman chemistry). However, there is ample evidence to suggest that sleep helps academic achievement, including the two studies below which incentivized sleep during final exam/assessment week and found similar results as ours,” Grossman explained.
The study, “Sleep quality, duration, and consistency are associated with better academic performance in college students”, was authored by Kana Okano, Jakub R. Kaczmarzyk, Neha Dave, John D. E. Gabrieli, and Jeffrey C. Grossman.