How the deep sleep phase affects your sleep quality
We all know the feeling — there's an important meeting or exam the next day, and sleep simply won't come. Too little sleep can take a toll on both body and mind, but fortunately, most sleep disturbances are mild and temporary. The fact remains: your body needs deep sleep. Here's why this sleep phase is so important, what happens in your body during it, and how you can improve your deep sleep.
How much sleep does a person need?
The question of how long you should sleep is actually quite simple to answer: until you feel rested!
Adults need an average of 6 to 10 hours of sleep per night, while infants sleep an average of 16 hours spread across day and night. As children grow older, their sleep cycles gradually align with adult day-night rhythms. Sleep requirements generally decrease with age.
The amount of sleep you need depends on external factors such as psychological and physical stress, diet, age, and medication. It can vary greatly from person to person.
What sleep phases are there?
Sleep is not a uniform state but is divided into different phases. In humans, we typically distinguish between five sleep phases:
- Falling asleep phase (Non-REM)
- Light sleep phase (Non-REM)
- Medium deep sleep
- Strong deep sleep (Slow-wave sleep)
- Dream sleep (REM phase)
Everyone goes through this five-part sleep cycle not just once, but repeats it at 90-minute intervals several times per night. Our sleep can be divided into non-REM and REM phases. REM stands for "Rapid Eye Movement". The falling asleep phase and light sleep are non-REM phases. In the essential deep sleep phase, the so-called REM phase, we hardly dream. It serves as the most important recovery phase during sleep.
What happens in the body during the deep sleep phase?
The deep sleep phase is extremely important for the body. During this sleep stage, the body releases growth hormones that not only make nails and hair grow but also repair damaged tissue. If you don't get enough deep sleep or don't reach the deep sleep phase at all, you often feel tired and unrested in the morning because your body hasn't had enough time to recover.
During the beneficial deep sleep phase:
- Body temperature drops
- Blood pressure decreases
- Heart rate slows
- Breathing calms down
This is when we can truly relax and rest. Even the immune system benefits during this sleep phase. Content learned during the day moves from short-term to long-term memory during the deep sleep phase, and the immune system learns along with it. According to findings from a German-Dutch research group, collected information about pathogens and germs is processed during deep sleep. The brain processes not only the day's impressions but far more information than previously thought during this sleep stage.
Sleepwalking or talking in your sleep commonly occurs during the deep sleep stage, and waking up is not as easy as during other phases.
How long does deep sleep last and when do we reach it?
On average, the body completes 6 sleep cycles per night. The first deep sleep phase occurs approximately 30–45 minutes after falling asleep. About 15–20% of each sleep cycle is attributed to the deep sleep phase, which can last up to an hour. The first four hours of sleep typically provide the most recovery, as the deep sleep phases are significantly stronger. From the third sleep cycle onwards, this stage becomes less intense.
What to do if you're not getting enough deep sleep?
Do you feel exhausted when you wake up and have the feeling you slept badly? This may be due to too little deep sleep. To improve your deep sleep phase, you can use some fairly simple strategies:
- Avoid stress
- As is often the case, the cause of sleep problems lies in too much stress and general overload, whether physical or psychological. Analyse your daily routine: where can improvements be made and how can your everyday life be made calmer? Relaxation methods such as autogenic training and yoga can help with lifestyle changes.
- Eat right
- Go easy on salt, sugar, fat and caffeine! Your eating habits directly affect the quality of your sleep. Bananas, walnuts, herbal teas and cranberries contain sleep-promoting ingredients, while caffeine, cigarettes and alcohol have a negative impact on deep sleep. Even though a glass of wine may make you pleasantly drowsy, the subsequent breakdown of alcohol in the body reduces sleep quality.
- Timing is everything
- If you can set your alarm so it doesn't ring during a deep sleep phase, you'll wake up fresher and more rested in the morning. Apps help analyse sleep cycles and find the right moment to wake up.
- Create a routine
- Maintain a regular sleep schedule. Our bodies are easy to programme, and the same applies to sleep. Going to bed at roughly the same time each day has a positive effect on your sleep cycles.
- Wind down in the evening
- Come to rest. Postpone stressful discussions or long phone calls to the next day. Pick up a book or listen to a relaxing podcast instead. Aimless scrolling on your phone has a counterproductive effect. Your bed's features also contribute significantly to sleep quality: adapt bedding, mattress and sleepwear to your personal needs and treat yourself to a weighted duvet for a sleep-promoting effect.
How much deep sleep does a person need?
Sleep needs vary greatly from person to person and are not constant. About 1.5 to 2 hours of deep sleep per night is considered normal and should ideally always be achieved. However, this requires a sleep period of 6 to 8 hours.
Do you dream during deep sleep?
Dreams are experienced particularly intensely during the REM phase, the so-called dream phase, where waking up is also easiest. According to researchers, this is the sleep stage where sensory impressions and other information are processed. However, dreams also occur during deep sleep — though these are shaped more by situations than by actions.
Melatonin — the body's inner clock
The endogenous hormone melatonin is responsible for the sleep-wake cycle. The lack of sunlight at night triggers the release of melatonin in the body, and tiredness sets in. For sleep disorders, melatonin can be prescribed by a doctor to help the body fall asleep.
A 2022 study also confirmed the positive effect of a weighted duvet on our melatonin levels. These heavy duvets, also known as therapy duvets and gravity duvets, exert gentle pressure on the body, which leads to increased release of "feel-good hormones" such as serotonin and oxytocin, while the stress hormone cortisol is reduced. For most users, this leads to deeper and more restorative sleep.
