A study of college students found that better sleep—specifically, higher quality, longer duration, and greater consistency of sleep—was associated with higher scores on quizzes and midterm exams.
While a multitude of studies have established the relationship between sleep and cognitive function, including measures of academic performance, most studies have used subjective, self-reported measures of sleep duration and quality. The current study, published in Science of Learning, used wearable activity trackers to objectively measure students’ sleep throughout an entire semester. The trackers recorded both sleep duration, based on the time in which the wearer has not moved, and sleep quality, based on the variability in heart rate that occurs throughout sleep stages.
Of the 100 students in an introductory chemistry class who were invited to participate, 88 completed the study. The investigators used the students’ sleep measures and in-class performance on quizzes and midterm tests to explore how sleep affects college students’ academic performance and whether this relationship differs by gender.
On average, students went to sleep at 1:54 AM and awoke at 9:17 AM. An analysis of variance found that participants who went to sleep before the median bedtime of 1:47 AM had a significantly higher overall score (ie, the sum of their scores on grade-relevant quizzes and exams) than those who went to sleep after. Additionally, those who woke up before the median wake-up time of 9:12 AM had a significantly higher overall score compared with those who woke up after that time. There were significant, negative correlations between overall score and both average bedtime (P <.0001) and average wake-up time (P <.001), such that earlier average bedtime and earlier average wake-up time were associated with higher scores.
The mean sleep duration in the sample was 7 hours, 8 minutes. The investigators found a significant positive correlation between mean sleep duration over the semester and overall score (P <.0005), as well as between mean sleep quality throughout the semester and overall score (P <.00005). When defining sleep inconsistency as the standard deviation of a participant’s daily sleep duration, they found a significant negative correlation between sleep inconsistency and overall score (P <.001), meaning that greater inconsistency was associated with a lower overall score.
The correlation between sleep duration and sleep quality was stronger in men than women, which the study authors wrote may mean that it may be more important for men to sleep for a long duration in order to achieve good quality of sleep. Sleep inconsistency and overall score were negatively correlated in men but not in women, potentially indicating that it is important for men but less important for to adhere to a regular sleep schedule to boost their academic performance.
According to a multiple linear regression, sleep duration, quality, and consistency together accounted for 24.44% of the variance in overall grade performance.
These findings, particularly the gender differences, led the authors to suggest that “it may be especially important to encourage better sleep habits in male students (although such habits may be helpful for all students).”
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 Sci Learn. 2019;4(1):16. doi: 10.1038/s41539-019-0055-z.