It may seem obvious that sleep is an important key to succeeding in college, but a new study shows just how critical it really is.
Two MIT professors found a strong relationship not just between students’ grades and how much sleep they’re getting, but also what time students go to bed, and how often they get a good night’s sleep.
Those are among the conclusions from an experiment in which 100 students in an MIT engineering class were given wrist-worn trackers, in exchange for the researchers’ access to a semester’s worth of their activity data. The research was conducted by MIT postdoc Kana Okano, professors Jeffrey Grossman and John Gabrieli, and two others. Their findings ranged from not surprising to quite unexpected.
One of the surprises was that individuals who went to bed after some particular threshold time — for these students, that tended to be 2 a.m., but it varied from one person to another — tended to perform worse on their tests no matter how much total sleep they ended up getting.
The study didn’t start out as research on sleep at all. Instead, Grossman was trying to find a correlation between physical exercise and the academic performance of students in his class 3.091 (Introduction to Solid-State Chemistry). In addition to having 100 of the students wear Fitbits for the semester, he also enrolled about one-fourth of them in an intense fitness class. The thinking was that there might be measurable differences in test performance between the two groups.
There wasn’t. Those without the fitness classes performed just as well as those who did take them. However, in the vast amount of data collected during the semester, some other correlations did become obvious. While the devices weren’t explicitly monitoring sleep, the wrist-worn trackers did detect periods of sleep and changes in sleep quality, primarily based on lack of activity.
These correlations were not at all subtle, Grossman says. There was essentially a straight-line relationship between the average amount of sleep a student got and their grades on the 11 quizzes, three midterms, and final exam, with the grades ranging from A’s to C’s.
The fact that there was a correlation between sleep and performance wasn’t surprising, but the extent of it was. Of course, this correlation can’t absolutely prove that sleep was the determining factor in the students’ performance, as opposed to some other influence that might have affected both sleep and grades. But the results are a strong indication, Grossman says, that sleep “really, really matters.”
The study also revealed no improvement in scores for those who made sure to get a good night’s sleep right before a big test. According to the data, “the night before doesn’t matter,” Grossman says. “We’ve heard the phrase ‘Get a good night’s sleep, you’ve got a big day tomorrow.’ It turns out this does not correlate at all with test performance. Instead, it’s the sleep you get during the days when learning is happening that matter most.”
This research also helped to provide an explanation for something that Grossman says he had noticed and wondered about for years, which is that on average, the women in his class have consistently gotten better grades than the men. Now, he has a possible answer: The data show that the differences in quantity and quality of sleep can fully account for the differences in grades. “If we correct for sleep, men and women do the same in class. So sleep could be the explanation for the gender difference in our class,” he says.