The science of sleep
- Mind Mesh
- Dec 5, 2025
- 3 min read
Why do we need sleep?
Everyone needs sleep, but its biological purpose remains a mystery. Sleep affects almost every type of biological tissue and organ in the body, from the brain, heart, and lungs to metabolism, immune function, mood, and disease resistance. In fact, recent research has shown that your brain plays a ‘housekeeping’ role that cleans up toxins that accumulate in your brain while awake.
A chronic lack of sleep, or getting poor-quality sleep, can affect the brain’s ‘plasticity’, which is the brain’s ability to adapt to input. Ever felt foggy after a poor night’s sleep? That’s your brain’s plasticity being diminished!
When people don’t get enough sleep, risks to their health arise, such as high blood pressure, cardiovascular diseases, migraines in women, diabetes and the immune system being compromised, to name a few.
The stages of sleep
There are two basic types of sleep: rapid eye movement (REM) sleep and non-REM sleep. Within non-REM sleep, scientists have defined 3 distinct stages of sleep. You cycle between REM and non-REM sleep multiple times in each sleep cycle, with increasingly longer, deeper periods of sleep occurring later in the sleep cycle.
Stage 1 non-REM sleep
Stage 1 non-REM sleep is the changeover from being awake to being asleep. During this short period of relatively light sleep, your heart rate and breathing slow and your eyes and muscles relax. This usually lasts several minutes. Your brain waves begin to slow.
Stage 2 non-REM sleep
Stage 2 non-REM sleep is a period of light sleep before you enter deeper sleep. Your heart rate and breathing slow even more and your muscles relax even further. Your body temperature drops and eye movements stop. Brain waves slow but this stage is marked by brief bursts of electrical activity. You spend more time in this stage than in other stages.
Stage 3 non-REM sleep
Stage 3 non-REM sleep is the period of sleep you need to feel refreshed in the morning. It occurs during longer periods during the first half of the sleep cycle. Heartbeat and breathing reach their lowest levels. Your muscles are relaxed and it may be difficult to wake you. Brain waves become even slower.
REM sleep
Occurs 90 minutes after falling asleep. Your eyes move rapidly behind closed eyelids. Mixed-frequency brain wave activity that becomes closer to when you’re awake, while your breathing becomes faster and irregular, and your heart rate and blood pressure increase to near waking levels. Most of your dreaming occurs during REM sleep, though it can occur during non-REM sleep as well. It is likely that both REM and non-REM sleep is needed to consolidate memories
How Much Sleep Do You Need?
Your need for sleep and sleep patterns (your sleep schedule) change as you grow older. There is no magical amount of sleep that works for everyone of the same age. For example, babies typically sleep for 16-18 hours a day, school-age children and teens need 9.5 hours, while most adults need 7-9 hours of sleep a night.
Tips for Getting a Good Night's Sleep
Exercise boosts the effect of natural sleep hormones, e.g., melatonin. Try to exercise at least 30 minutes a day but not for a few hours before bedtime.
Avoid caffeine, nicotine, and alcohol before bed. Stimuli such as these may seem calming, but they actually disrupt sleep.
Relax before bed. Giving yourself time to wind down is crucial for a good night's sleep; stress can cause hormonal changes that make you tense and disrupt sleep.
Keep your room comfortable. TV and your phone aren't your only distractions in your bedroom. The general ambience can affect your sleep too. Make sure your room is as silent and dark as possible, avoid loud sounds and keep your room cold.
Set a schedule, or a sleep ritual. Rituals help signal the body and mind that it's coming to be time for sleep; you could drink a glass of warm water or milk or take a bath.
You can eat! But not too much. Avoid eating big meals 2-3 hours before bedtime. And if you’re really peckish, have a small, healthy snack like an apple or some crackers.
Reserve your bed as a place for sleep. Don't make your bed a place for doing assignments, texting or watching TV. A bed needs to be a stimulus for sleeping.
If you’re having trouble sleeping, go seek a doctor. If you feel like you have a condition that makes you sleepy during the day or keeps you awake at night, it's best to check with your doctor. Most sleep disorders can be treated easily.
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