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Students in an MIT class wore Fitbits not so they could count their steps and shape up, but so a professor could count how many Z’s they were getting — and determine the effect of sleep on their grades.

Jeffrey Grossman gave 100 students in his introductory chemistry class last fall the activity-tracking watches. One major finding: It can really pay for a student to get enough rest.

Grossman said the study found a “dramatic increase in academic performance with just an hour more sleep per night. . . . You’re going from a C to an A,” reinforcing previous research about how crucial sleep is for students.

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The results were published Tuesday in the journal npj Science of Learning. Postdoctoral fellow Kana Okano was the lead author. Professors Grossman and John Gabrieli and two others were also authors, the Massachusetts Institute of Technology said in a statement.

Arn Eliasson, the editor-in-chief of the journal Sleep and Breathing, said the study is exciting because it has a solid sample size and relies on objective data from the Fitbits rather than self-report data from questionnaires, the usual avenue of data collection in sleep studies.

However, Eliasson, a professor of medicine at the Uniformed Services University of the Health Sciences in Maryland, said a weakness of the study is the subjects were homogenous, all in an advanced class at a high-ranking university.

“How generalizable are these results to any other setting?” he said.

Roxanne Prichard, a professor of psychology and neuroscience at the University of St. Thomas in Minnesota with a focus on sleep and circadian rhythm, said that although the study is not randomized, it is still valuable, especially because it is a longitudinal study with data from an entire semester.

“An MIT chemistry class is not going to be the same as a national sample . . . but I think the general conclusions are sound,” she said.

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Researchers at MIT found “quantitative, objective evidence that better quality, longer duration, and greater consistency of sleep are strongly associated with better academic performance in college,” the study abstract said.

Grossman said researchers came up with other interesting findings along the way.

One finding might have big implications for hardcore night owls. Researchers found that students who went to bed after 2 a.m. got worse grades than their peers, even if they got the same amount of total sleep.

Researchers also found that students who got enough sleep every night scored better than their peers who had inconsistent sleep schedules but caught up and averaged the same amount of sleep.

Grossman also said that the study found that getting enough sleep the night before the test won’t cut it — students saw grade improvements only when they got a good night’s sleep for multiple nights in a row before a big test.

The women in Grossman’s class maintained better sleep schedules than the men, which led Grossman to wonder whether that is the secret of women’s academic success.

“We have consistently found that women get better grades than men on average,” he said. The data showed that the differences in quality of sleep between the two groups could fully account for the differences in their grades. After correcting for sleep, Grossman said, “Men and women do similarly in the class.”

Grossman hopes the findings of the study will encourage students to finally get more sleep.

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“You can tell them all you want, ‘Oh, you need to get sleep, it’s so important for you,’ ” he said. “Having a few more motivating factors couldn’t hurt . . . and I think this is a really good one.”

Prichard said this study may help to dispel a common myth among college students about sleep. She said some students joke it’s impossible to get enough sleep, receive good grades, and have fun; you can only pick two.

“To get this amount of data in an objective manner in a real-life classroom is really great . . . and motivating for a lot of students,” she said. “It dispels the idea that if you work all night and burn the candle on both ends, you’ll perform better.”


Maria Lovato can be reached at maria.lovato@globe.com. Follow her on Twitter @maria_lovato99.