Introduction
Human beings are the only species that deliberately deprive themselves of sleep for no apparent gain. Dr Matthew Walker, neuroscientist and author of Why We Sleep, highlights sleep's profound impact on human health. Rather than focusing on disease risk, this article explores how sleep affects learning, memory and mental clarity.
Many students experience poor focus, mental fog, and reduced concentration. Research increasingly suggests that these issues may stem from something simple: poor sleep. A 2019 study at the University of York found that 74 per cent of university students are sleep-deprived. Academic pressure, financial stress, moving away from home and maintaining a social life all affect sleep quality and quantity.
Most students do not realise they are sleep-deprived because they have adapted to functioning in a fatigued state, often masking symptoms with caffeine or energy drinks.
The science of sleep
Every species requires sleep. For humans, the National Sleep Foundation recommends an average of eight hours per night. However, sleep quality matters as much as sleep duration. Even if you aim for eight hours, you may not be sleeping productively.
Sleep consists of four stages, divided into non-REM and REM phases, each with a distinct role in cognitive performance.
1. First stage of non-REM
As you drift off, you enter light sleep. You are relaxed but easily awakened for around ten minutes.
2. Second stage of non-REM
Your body prepares for deep sleep. Your heart rate and temperature drop, and your muscles may twitch.
3. Third stage of non-REM
This is deep sleep. You are not easily awakened.
4. REM sleep
Brain activity increases, your pulse quickens, and you may have vivid dreams. REM sleep is essential for learning and memory formation. Studies show that low REM sleep predicts faster decline on certain cognitive tests.
Why sleep matters for cognition
Sleep supports learning and memory in two key ways:
Sleep before learning
You need sleep before learning to prepare the brain to absorb new information. A sleep-deprived person cannot focus attention optimally and therefore cannot learn efficiently. It is like trying to use a laptop that has run out of charge.
Sleep after learning
After learning, the brain processes and temporarily stores information. Sleep then consolidates memory by transferring information from short-term to long-term storage, making it easier to recall. It's like saving files onto a USB stick you can access later.
If you don't get enough sleep, the four stages fall out of sync. New information stays in short-term storage and gradually fades.
Tips from Dr Walker for better sleep
Stick to a sleep schedule
Your internal clock follows a specific sleep-wake cycle. Going to bed at 22:00 one night and 02:00 the next disrupts your circadian rhythm. Catching up on sleep is not always effective.
For more on circadian rhythms, see the Siffre cave study.
A small PSA: this does mean no more late nights in the club. A good social life is important, but moderation is key.
Exercise, but not too late
Aim to finish exercising 2 to 3 hours before bedtime.
Avoid large meals and excessive drinks
A snack is fine, but large meals can cause indigestion. Drinking too much can make you wake up repeatedly to use the bathroom.
Create a dark, cool, tech-free bedroom
Limit distractions such as standby lights, phone notifications and warm temperatures.
Relax before bed
Stress and anxiety make it difficult to sleep, which then causes more stress about not sleeping. Schedule time to wind down and set a work cut-off time.
Avoid naps after 15:00
Late naps make it harder to fall asleep at night.
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