Students who have a chronic lack of sleep have lower grades and find it harder to concentrate, finds Leiden University. Around a third of students do not feel well rested enough to be able to study properly. The results come from a national survey by the Netherlands Association for Sleep Wake Research, Leiden University and the Netherlands Brain Foundation among almost 1,400 healthy students at Dutch universities.

More Than a Third Have Too Little Sleep

Young adults need 8 to 9 hours sleep in order to able to function properly (according to research by the National Sleep Foundation). More than a third of the students surveyed do not feel properly rested during their study activities. Students who suffer a chronic lack of sleep score significantly lower on their final exam in the current academic year (an average of 0.8 lower) and have a significantly lower average grade than students who have enough sleep (an average of 0.5 lower). They also find it harder to concentrate while studying.

Relationship Between Sleep, Concentration Among Students

Lead researcher, Kristiaan van der Heijden, PhD, from Leiden University, says in a release: “We have known for a long time that lack of sleep can cause concentration problems and poorer study performance, but we can now show this for the first time among students in Dutch higher education.”

Chronic Lack of Sleep

The average Dutch student goes to bed at 23.35 hrs. and takes 26 minutes to fall asleep. They get up at around 8.17 hrs., which means they have slept 8 hours and 16 minutes. 65% of the students say they do not have enough sleep: they would like to sleep for an hour and a half longer. 28% of the respondents receive just the right amount of sleep and 7% would be happy to sleep less.

Evening or Morning Types

Of the respondents, 32% say they are evening types and 7% that they are morning types (61% say they are neither). The evening types go to bed later (00.15 hrs.) than the average (23.20 hrs.) and morning types (22.35 hrs.). The evening types sleep significantly shorter (8 hours and 6 minutes) than the average (8 hours and 20 minutes) and the morning types (8 hours and 28 minutes).

More Than a Third Do Not Feel Well-rested Enough to Study Properly

The evening types more often find it difficult to keep their eyes open if they are sitting for some time in a lecture or working group (18% versus 12% and 8%) and are less often interested in studying because they feel too sleepy (36% versus 22% and 13%). The lack of sleep has clear consequences for their study results: the final exam grade (6.9) is considerably lower than the average types (7.2) and morning types (7.3).

Regular Bedtime Is Crucial

Van der Heijden says, “As the evening types sleep for less time every day than the average and morning types, they build up a sleep deficit over time. Evening types are more likely to have to get up in the morning while their biological clock hasn’t yet given them a signal to wake up. This can have a negative effect on the rest of the day.” Although people often have a genetic propensity to be evening types, they can reduce the problem by paying attention to good sleeping habits. “Regular bedtimes are extra important for these people and sleeping through to the afternoon in order to make up for lost sleep is disastrous for their sleep rhythm,” he says.


Students almost all agree that drinking coffee or other caffeine-containing drinks after dinner has a negative influence on sleep. But there some negative habits and behaviors that many students believe are positive, and vice versa. As an example, drinking alcohol is another area where there are misconceptions: 30% believe that it affects sleep positively, while research has shown that the opposite is the case.

Too Little Known About Healthy Sleep Behavior

It appears from the research that students who have a good understanding of healthy sleep habits obtain higher grades. Dr Laura Smit-Rigter from the Brain Foundation comments: “Given the importance of good sleep, people really do need to have the right knowledge and then apply it. The Brain Foundation has a special web page where people can learn what they can do to sleep better.”