Tweens and sleep: One extra hour in bed resulted in better grades, study finds

Trine Jensen-Burke

It is probably the single most important thing we can do for our health.

And now recent research is teaching us that sleep doesn’t just matter to our overall wellbeing, mood and immune system, it actually also makes a huge difference when it comes to academic success.

In fact, according to a recent study, researchers found a strong link between students’ grades and how much sleep they were getting at night.

As well as this, what time the students went to bed at mattered, as it turned out. And so did the consistency of their sleep habits.

The problem? Just getting one good night’s sleep before a test or exam is no good, the US researchers found. From the studies, they came to realise that it takes several nights in a row of good sleep to actually make a difference.

The study, which was conducted at Massachusetts Institute of Technology and published in the journal Science of Learning, saw 100 students given Fitbits in order to track their activity 24/7 – in exchange for the researchers’ access to a semester’s worth of their activity data.

One of the most interesting finds was that bedtime – as in, what time the students went to bed at – seemed to matter the most when it came to grades and academic success. The researchers discovered that apparently 2am was the most common threshold time. As in; students who went to bed after this time – no matter how long they were able to sleep in the following morning – performed less well on tests, regardless of total hours sleep they had gotten.

Professor Jeffrey Grossman, who was one of the lead authors of the study, explains that the project has initially started out as a test to see if they could prove that physical exercise made a difference to academic performance. Disappointedly, Grossman concluded they were not able to find such a correlation but soon discovered that with the vast amount of data they collected that semester, other correlations did become obvious.

In fact, so strong were the stats they discovered, that his team were able to prove with a lot of certainties that there is essentially a straight-line relationship between the average amount of sleep a student got and their grades on 11 quizzes, three midterms, and the final exam.

The night before doesn’t matter

“There’s lots of scatter, it’s a noisy plot, but it’s a straight line,” Grossman said to MIT News. The fact that there was a correlation between sleep and performance wasn’t surprising, but the extent of it was, he says. 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.”

“Of course, we knew already that more sleep would be beneficial to classroom performance, from a number of previous studies that relied on subjective measures like self-report surveys,” Grossman says. “But in this study, the benefits of sleep are correlated to performance in the context of a real-life college course, and driven by large amounts of objective data collection.”

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.”

Another surprising finding is that there appears to be a certain cutoff for bedtimes, such that going to bed later results in poorer performance, even if the total amount of sleep is the same. “When you go to bed matters,” Grossman says. “If you get a certain amount of sleep — let’s say seven hours — no matter when you get that sleep, as long as it’s before certain times, say you go to bed at 10, or at 12, or at 1, your performance is the same. But if you go to bed after 2, your performance starts to go down even if you get the same seven hours. So, quantity isn’t everything.”

Quality of sleep also mattered, not just quantity. For example, those who got relatively consistent amounts of sleep each night did better than those who had greater variations from one night to the next, even if they ended up with the same average amount.