Your Body Wants 8 Hours of Sleep: Here’s Why

Dr. Matthew Walker, a neuroscientist, professor, and bestselling author of Why We Sleep, said, “Sleep is the single most effective thing we can do to reset our brain and body health each day.” He also noted in his book Why We Sleep: Unlocking the Power of Sleep and Dreams that sleep is Mother Nature’s best effort yet at contra-death, and when you hear neuroscientists say that about sleep, it makes you want to rethink your 5 hours of sleep routine. There’s a saying that most workaholics like to say: “I’ll sleep when I’m dead.” I love using that quote too because I sometimes feel like sleep is overrated, but it’s not. We need sleep to function, to focus, to manage stress, to recover, and to stabilise our emotions. Maybe that’s why most workaholics are constantly anxious and stressed because they don’t get enough sleep.

Why is Sleep Important?

To first understand the importance of sleep, you first have to understand what is happening in our brains and bodies when we sleep. When you fall asleep, your brain is still active, and the brain activities that happen during sleep, scientists categorise into 2 stages. REM sleep stands for rapid eye movement sleep, a unique stage of the sleep cycle marked by high brain activity, vivid dreaming, and temporary muscle paralysis. NREM stands for non-rapid eye movement sleep, which makes up about 75% to 80% of total adult sleep time.

During REM, this is when your brain processes daily information, sorts data, and converts short-term memories into long-term storage. It also processes complex emotions, which regulates your daily mood and lowers stress. This is why infants sleep almost all the time because 50% of their sleep is in REM, which supports central nervous system growth.

NREM has 3 stages. N1 is when you enter light sleep. This is when you transition from wakefulness to sleep. N2 is when you enter deeper light sleep, characterised by sleep spindles and K-complexes on an EEG, which help block out external noise and process procedural memory. And lastly, N3 consists of slow-wave or deep sleep. This is the deepest non-REM sleep, dominated by slow delta brain waves.

These stages serve as the primary phase for physical restoration, immune system strengthening, cardiovascular health, tissue and bone repair, growth hormone release, metabolic health, and declarative memory consolidation. Sleep is essential for memory consolidation and motor skill “automaticity.” During sleep, the brain reprocesses information, which can lead to creative insights and problem-solving breakthroughs, clearance of toxic proteins linked to Alzheimer’s disease. And when it comes to emotional wellbeing, it does wonders too. Sleep functions as a form of overnight emotional first aid, helping to detach painful emotions from memories, allowing us to wake up with clearer perspectives.

The 4 Sleep Cycles

When you fall asleep, you typically enter NREM stage 1 and then cycle between NREM stages 2 and 3. After that, you go into REM sleep and start dreaming. After the first REM cycle, you start a new sleep cycle and go back into stage 1 or 2, and the cycle starts over. One cycle normally takes about 90 minutes to 2 hours before another begins. Most people go through 4 or 5 cycles per night if they get a full 8 hours of sleep.

What Happens If You Don’t Get the Full 8 Hours of Sleep?

When you don’t get enough sleep and get about 6 hours or less, it takes a toll on your cognitive performance and immune function and increases the risk of serious health conditions like heart disease, cancer, and Alzheimer’s.

A study from University of Ferrara shows that the spring “spring forward” transition in Daylight Saving Time (DST), where people lose 1 hour of sleep, disrupts sleep and temporarily elevates stress on the cardiovascular system. They found a 4% to 29% increase in acute heart attacks during the first week following the shift, with heart attacks decreasing by 21% during fall, where people get an extra 1 hour of sleep. If losing just 1 hour of sleep can affect your heart, then think about losing 3 hours of sleep?

For one to wake up feeling rested and refreshed, they have to get all the sleep cycles, the NREM and REM. And REM is the most important one, to the point that your brain would try to make up for the times you haven’t had enough REM sleep, aka the REM sleep rebound effect. This is when your brain tries to get back some of the dream/REM sleep it’s been losing if you have been using sedative prescriptions or using alcohol to fall asleep. You end up getting intense REM sleep.

Dangers of Sleep Deprivation

Chronic Risks: Sleeping less than 7 hours regularly raises the risk of cancer, heart disease, diabetes, and Alzheimer’s disease.

Cognitive Decline: Getting only 6 hours of sleep impairs your focus, memory, and reaction times as much as being legally drunk.

Mental Health: Short sleep increases anxiety, depression, and emotional instability.

Metabolism: Sleep loss triggers hunger hormones, suppresses fullness hormones, and increases the risk of weight gain.

Testosterone Decline: Chronic sleep of only 5 to 6 hours a night can reduce a man’s testosterone levels to that of someone 10 years older and significantly impairs the cardiovascular and immune systems.

Sleep Deprivation and ADHD Connection

A study review from Douglas Mental Health University Institute found that between 25% and 80% of individuals with Attention-Deficit/Hyperactivity Disorder (ADHD) experience chronic sleep problems, and a lack of sleep directly worsens core ADHD symptoms, creating a challenging feedback loop.

ADHD is often associated with comorbid sleep disturbances. Sleep disturbances may be a risk factor for development of the disorder, a symptom of the disorder, or a comorbid condition affected by a similar psychopathology.

Various studies have examined the impact of sleep deprivation on the presence/exacerbation of ADHD symptomology, as well as longitudinal and concurrent associations between different sleep disturbances and ADHD, yet the notion of sleep disturbances as a predecessor to ADHD remains unclear.

The majority of studies with typically developing children and children with ADHD have demonstrated that sleep deprivation can result in deficits in neurobehavioral functioning that resembles or exacerbates ADHD symptoms.

In the study, researchers assessed the effect of cumulative sleep deprivation on neurobehavioral functioning of both typically developing children and children with ADHD. In both studies, it was found that sleep deprivation resulted in a significant decrease in performance on the continuous performance task, a neurobehavioral task requiring sustained attention and behavioural inhibition that is commonly used in the evaluation of inattention and impulsivity in children with ADHD.

Furthermore, in the study by Gruber et al., performance of the ADHD group deteriorated from subclinical levels of inattention to clinical levels of inattention following sleep deprivation, emphasising the negative impact on ADHD symptomology.

Sleep Deprivation and Weight Loss Connection

When you are trying to lose weight, sleep is probably the best thing you can do for yourself, and getting enough sleep will help in your journey. But how does sleep really affect weight loss?

To lose weight, you need to be in a calorie deficit, and to be in a calorie deficit, you need to rely on appetite-regulating hormones. The leptin hormone signals to the brain that you are satisfied and no longer hungry, and the ghrelin hormone signals to the brain that you are not full and not satisfied and still hungry. When you get less than 6 hours, the leptin hormone decreases by 80% and the ghrelin hormone increases by 28%, and you end up eating more, about 300 to 400 calories after, and you experience increased cravings for carbs such as pasta and bread, as well as sugary and sodium-heavy foods.

If you do manage to stay in a calorie deficit and exercise but don't get more than 6 hours of sleep, the weight loss will come from muscle and not fat. Researchers from the Institute for Physical Activity and Nutrition recruited 13 healthy young adults consisting of seven male and six female participants. They were subjected to one night of total sleep deprivation and normal sleep in a randomised crossover design.

They assessed their anabolic and catabolic hormonal profiles, postprandial muscle protein fractional synthesis rate, and gene markers of muscle protein degradation. In simpler terms they looked at the hormones that help build and break down muscle, how much new muscle protein the body made after eating, and signs of muscle breakdown.

The study found that sleep deprivation reduced the body’s ability to build new muscle protein by 18%. The male participates but not the female participants, experienced a decrease in protein production during sleep deprivation. The male participants also had lower testosterone levels, while cortisol, the stress hormone, was 21% higher when they were sleep-deprived.

The study concluded that ongoing sleep loss can put the body under stress, increase the risk of metabolic problems, and contribute to muscle loss and reduced muscle function. It also found that even one night of sleep deprivation can make it harder for the body to build muscle, reducing muscle protein production by 18%. This was linked to higher levels of cortisol, the stress hormone, and lower testosterone levels in male participants.

This was the first study to show that even one night of poor sleep can reduce muscle protein synthesis, which is important for maintaining and building muscle. This suggests that when we don't get enough sleep, the body will break down protein for fuel, hence causing one to lose more muscle and not fat when they are in a calorie deficit.

8 Strategies for Better Sleep

These are some of Dr. Matthew Walker's strategies to help one have better sleep.

1. Temperature Control

Keep the bedroom cool, ideally around 18°C (65°F), as your body needs to lower its core temperature to help you fall asleep and stay asleep.

2. Be Consistent

Go to bed and wake up at the same time every day, including weekends. Keeping the same schedule helps your body maintain a consistent sleep routine. If you want to sleep a little longer on the weekend, consider taking a nap later instead, while still waking up at your usual time.

3. Darkness

A darker environment signals to your brain that it’s time to wind down and prepare for sleep. Use blackout curtains to keep your bedroom dark and during the last hour before bed, dim the lights or switch off some of them.

4. Walk it Out

If you cannot fall asleep after 30 minutes, get out of bed and do something relaxing, such as reading a book or listening to a calm podcast. This can help you avoid lying awake and becoming frustrated or stressed about not sleeping. Once you start feeling sleepy again, return to bed and try to fall asleep.

5. Remove Clocks

Try not to keep a clock where you can easily see it from your bed. Constantly checking the time can make you worry about how many hours of sleep you have left, which can make it even harder to relax and fall asleep. If you wake up during the night, avoid checking the clock and focus on getting comfortable and going back to sleep.

6. Don’t Drink Alcohol Before Sleep

Alcohol will knock you out and make you fall asleep, but it will interfere with natural sleep by reducing REM sleep, is important for getting restful, quality sleep.

7. Don’t Drink Coffee or Caffeine at Night

Caffeine is a stimulant, so it can keep your brain alert when your body is trying to wind down. Even if you can fall asleep after drinking coffee, it can still affect how deeply you sleep and cause you to wake up feeling tired. Try to avoid coffee, energy drinks and other caffeinated drinks in the hours before bed.

8. Avoid Blue Light an Hour Before Bed

The light from your phone, iPad or TV can signal to your brain that it’s still daytime, making it harder to wind down for sleep. And it’s not just the light. Doomscrolling through TikTok or social media keeps your brain stimulated and engaged when it should be relaxing. The constant stream of content can make you want to keep scrolling, leading to sleep procrastination and pushing your bedtime later than planned.

Sleep is not a luxury, it is a basic biological need that supports almost every part of our health, from our immune system and emotional wellbeing to memory and recovery. While we sleep, our brains processes memories, strengthens learning and carries out important housekeeping to clear away metabolic waste.

So, the next time you feel like skipping sleep to watch Netflix, remember that those extra hours of screen time can affect how you feel and function the next day. And I guess sleep is not overrated, many of the health issues we face today can be improved or better managed by getting enough good-quality sleep.