An idea that seems to make sense

The idea that sleep impacts on learning has plenty of intuitive weight, simply because everyone has experienced feeling tired and unable to concentrate, but the science behind this is quite new and really interesting. There are basically two ways to look at the relationship between sleep and learning (or school performance): firstly, by considering what happens when children don’t get enough sleep, and secondly, by assessing the science of what sleep does for the brain.

First, a brief anatomy of sleep. There are two broad stages of sleep: rapid eye movement (REM) and non-rapid eye movement (NREM). Each of these has sub-stages. When we fall asleep, we slip through stages one and two of NREM and into the deep sleep stages three and four, where brain activity is at its slowest, before moving into REM sleep. At this point, brain activity becomes much more rapid, and if we are awakened, we often report experiencing dreams. Adults cycle through these stages roughly every 90 minutes, while for infants it’s more like every 30-50 minutes. In children under two, and indeed in all young mammals, REM forms a much higher proportion of sleep, leading some to suggest that the main role of REM sleep is supporting brain development. In older children, NREM is more dominated by stages two and three, or ‘slow wave sleep’, again suggesting that slow wave activity in the brain might be especially associated with learning.

Well rested pupils do perform better in school

Persistent self-reported sleep problems at 7-9 years have been shown to predict teacher assessed academic outcomes 4 years later[i]. In adolescence, shifting body clocks (staying up later, waking later) may produce an accumulating sleep deficit through the week because schools start at a fixed time. There is evidence that for teenagers, a delay in school start time by as little as an hour can have tangible positive impacts on sleep duration and school performance[ii] [iii]. Sleeping longer is not always better though; a study of Norwegian young adults suggests that sleeping too much or too little is associated with increased risk for failed examinations[iv].

Sleep deprivation stunts learning

There are a few studies looking at the effects that short-term sleep deprivation has on the behaviour of typically developing children and adolescents. The research on sleep deprivation in children typically looks at the relationship between how well children sleep and their performance at school the next day. In 9-14 year olds, good sleep quality, feeling rested at school and having a distinct bed time have been associated with better functioning at school[v], while 10-14 year olds deprived of sleep for a single night have shown deficits in abstract thinking and verbal creativity[vi]. Looking over the course of a week, just one hour of sleep deprivation each night in 6-8 year olds resulted in changes in brain activity during simple tasks of attention and speech perception[vii]. So both chronic and acute sleep deprivation make an impact on how children function during the school day.

Brain imaging has shown that after chronic sleep deprivation in adolescents, brain areas that actively maintain attention have to work much harder to sustain performance during a memory task[viii]. So even those children who manage to maintain their performance at school may be working much harder to do so after a poor night’s sleep.

Interestingly, 75-80% of children with neurodevelopmental conditions (including autism, epilepsy, cerebral palsy and ADHD) have chronic sleep disturbance, including difficulty falling asleep, frequently waking in the night and waking early in the morning [ix]. Studies of have shown that poor sleep predicts some difficulties with cognitive skills relevant to learning in children with Downs syndrome[x] and autism[xi], whilst epilepsy seems to disrupt memory consolidation during sleep. Also, a recent study of secondary aged students with ADHD showed that sleep problems reduced the effectiveness of an academic and organisation intervention on school grades[xii]. These findings suggest that sleep disturbances may partly underlie the academic difficulties experienced by pupils with neurodevelopmental conditions.

Sleep consolidates learning …

Sleep is thought to be an active part of learning, with around 83% of published studies showing an association between sleep and memory[xiii]. Studies looking at the role of sleep in learning tend not to deprive participants of sleep, but rather teach them a task, then test them after a set interval which is either filled with normal sleep (over night or a daytime nap) or being continuously awake; that way participants can be compared with one another following the same amount of time after learning the task, but with only half the group having slept. In adults, sleep benefits all types of memory task tested. Broadly speaking, memory tasks can either be explicit, where the participant knows they are learning and actively does so, such as learning to associate word pairs, or they can be implicit, where the participant tends to be unaware they are learning, for example repeatedly performing a cued finger tapping sequence or other motor task[xiv]. Studies suggest explicit learning is supported by slow wave sleep during NREM periods, while implicit learning is more supported by REM sleep[xv]. Indeed, boosting slow electrical activity in the brain artificially by applying a weak electric field to the head during sleep was found to increase explicit memory performance[xvi]!

… in children, too

A recent review of published studies of children and adolescents found a good deal of evidence that explicit memory is supported by sleep, just like in adults[xvii]. Since performance in exams generally relies on remembering facts, which is an explicit task and is therefore likely to be sleep-dependent, this points to one reason why well-rested children perform better on exams. Early to bed the day before tests! However, in the review, only one study showed a benefit for implicit memory. The authors suggested that this may be due to differences in how sleep tends to be measured in child and adult studies.

So get a good night’s sleep

The verdict here is a resounding neuro-hit. The extent to which sleep impacts on learning depends on the degree and duration of sleep deprivation and type of material being learned; but yes, well-rested children will perform better in the classroom in both the short-term and the long-term.

Further resources

Dr Robert Stickgold talks about sleep and memory at TEDx.