The less college students sleep, the worse their end-of-term grades, according to two-year study

The less a college student sleeps every night, the lower their end-of-term grade-point average will be, according to a two-year study of the sleep habits of more than 600 college freshmen that was published Feb. 13 in the journal PNAS.

Researchers found that every lost hour of average nightly sleep at the start of an academic term was associated with a 0.07-point drop in a student’s end-of-term GPA. When a student slept less than six hours a night, the effect on a student’s grades was even more pronounced, said David Creswell, the lead author of the study and a professor in psychology and neuroscience at Carnegie Mellon University.

Sleep, especially undisturbed sleep, helps the brain process and retain information it has learned. And when someone is sleep-deprived, attention span and memory also are impaired.

The average student in the study fell asleep at about 2:30 a.m. Barely any of the students went to bed before midnight. And, on average, they slept 61/ hours a night.

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Sleep recommendations shift by age, and the amount of sleep an individual needs can vary. In general, for teenagers, the recommendation is eight to 10 hours of sleep. For those ages 18 to 25, it drops to seven to nine hours.

Creswell and the team of researchers conducted five studies, recruiting college freshmen taking courses in a range of majors at Carnegie Mellon, the University of Notre Dame and the University of Washington. To monitor sleep, the students wore either a Fitbit Flex or a Fitbit HR for the entire academic term, a spring semester or a winter quarter, depending on the school, Creswell said.

After controlling for other factors — such as whether students take naps, their number of class credits and their GPA the previous term — the researchers found that average nightly sleep continued to predict a student’s end-ofterm GPA. What time a student went to bed and whether their bedtime varied day-to-day did not seem to play a role, Creswell said.

It’s unclear why less sleep would cause someone to have a lower GPA, Creswell said.

Sleeping for longer, uninterrupted periods of time allows for REM sleep, a period of unconscious rapid eye movement that corresponds with high activity in the brain.

Creswell said he suspects a regular pattern of insufficient sleep creates a “sleep debt” over time, leaving students unable to concentrate.

Nightly sleep duration predicts grade-point average in the first year of college PNAS