Just like food and water, sleep is essential to our survival.
When we sleep, our bodies go through an intricate process of recovery and healing, and if we don’t get enough, our overall health quickly declines.
But what exactly happens when we fall asleep, and why is sleep so important? In this post, we’ll find out.
What Happens When You Sleep?
During the hours of sleep, your body goes through 4-6 sleep cycles.
Each cycle contains two major sleep stages; non-rapid eye movement (NREM) sleep and rapid eye movement (REM).
The non-rapid eye movement (NREM) phase is broken down into three sub-stages, known as N1, N2, and N3. These are followed by the final stage in the cycle, rapid eye movement (REM).
The Four Stages of The Sleep Cycle
1. Stage One (N1)
Stage one (N1) is also known as the light sleep stage. We spend just 5% of our total sleep time within the N1 stage, which equates to around 1-5 minutes per cycle.
This is when your body and brain shift from an alert state of wakefulness into the beginning of sleep. Breathing, brain waves, and eye movement start to slow down, and heart rate decreases slightly.
2. Stage Two (N2)
During this stage, we begin to drift off into a deeper sleep. Heart rate continues to decrease, and our body temperature drops along with it.
During stage two, sleep spindles (short and powerful bursts of brain activity) and K-complexes (high voltage, low-frequency brain waves) occur. Both of these mechanisms play a crucial role in memory consolidation and help to maintain sleep.
Stage two lasts an average of 25 minutes during the first sleep cycle of the night and gets longer with each subsequent cycle. Overall, this takes up the largest percentage of our nightly sleep, around 45% in total.
Interestingly, if you’re prone to grinding your teeth during slumber, you’re most likely to do this in stage two.
3. Stage Three (N3)
Also known as slow-wave sleep, this is the deepest of all the Non-Rapid Eye Movement (NREM) stages.
Delta waves are at their lowest frequency and their highest amplitude, which makes this sleep stage the most difficult to wake up from. If your alarm clock goes off during N3, you’re likely to be groggy for up to an hour before you begin to feel alert.
But this deep sleep stage is the most physically restorative of them all, making it crucial to recovery. Blood flow to the brain decreases, allowing more blood and oxygen to flow to muscles and other tissues, helping them to repair and grow. Crucial metabolic hormones from the pituitary and adrenal glands are also released during this time.
We spend around 25% of our total sleep in stage three, but as we get older, this number decreases.
4. Stage Four (REM)
During Rapid Eye Movement (REM), our eyes begin quickly moving back and forth, giving this stage its name.
This is the final sleep stage before the cycle begins again. Breathing quickens, and blood pressure and heart rate become more erratic.
REM sleep is where the majority of dreaming occurs. Muscle tone also decreases, known as ‘muscle atonia,’ which prevents us from physically responding during dreams.
But while most people experience muscle atonia during REM sleep, some don’t. This disorder is known as ‘REM sleep behavior disorder’ and causes people to lash out physically as they dream.
Without REM sleep, neural pathways become weakened and damaged, and memory loss can occur, which is why this final stage is considered the most vital for brain restoration.
The best time to wake up is at the end of the REM sleep phase, as this is when the brain enters a ‘hyper-associative’ state, making us more alert, creative, and better at problem-solving.
The REM stage takes up around 25% of our overall sleep. During the first sleep cycle, you may only experience REM for 10 minutes, but by the final sleep cycle of the night, REM can last for up to an hour.
Why is Sleep so Important?
We all know what happens when we don’t get enough sleep. We feel tired, groggy, and irritable, and if the pattern continues for several nights in a row, we’re more prone to getting sick.
So, it’s obvious that sleep is crucial to our wellbeing, but why?
Sleep helps our bodies and brains in many different ways, including the following:
1. DNA Regeneration
Sleep gives our cellular tissue and DNA the chance to repair and regrow. Without a properly functioning sleep cycle that balances all four stages, our cells not only miss out on this repair phase, they actually begin to break down at a faster rate.
“I think this is one of the key reasons we need to sleep,” says neuroscientist Lior Appelbaum from Israel’s Bar-Ilan University. “There is repair going on in the day, but sleep allows you to catch up.”
Applebaum was part of a team of scientists who examined the sleep patterns of genetically engineered zebrafish, and this futuristic study found some surprising results.
During waking hours, the fish’s chromosomes were relatively stationary, allowing broken DNA strands to accumulate. But during sleep, the chromosomes begin moving more rapidly and changing shape. It allows the body’s repair mechanisms to fuse DNA back together, healing the damage done during waking hours.
As a result, fish with the greatest levels of sleep had a marked decrease in DNA deterioration compared with those who were kept awake for longer.
2. Improved Mental Health
The relationship between sleep and psychological wellbeing is well documented, but new research has highlighted just how crucial a full night’s sleep can be.
A recent study featured in the JAMA Psychiatry journal found an undeniable link between poor sleep and increased suicide rates in older adults. Two particular risk factors stood out; those with difficulty falling asleep and those who fell asleep naturally but missed out on the full spectrum of restorative sleep stages we discussed above.
Further research has shown that 90% of patients being treated with depression also have insomnia and that the cause for this psychiatric imbalance is often lack of sleep itself rather than a symptom.
And it’s not just depression that’s linked to poor sleep. Chronic insomnia is also a risk factor for developing anxiety disorders in later life.
So, while the odd sleepless night here and there is nothing to worry about, inadequate sleep over a longer period can hugely impact your mental health.
3. A Stronger Immune System
Sleep plays an important role in our immune health, which affects every organ in our body.
When our immune system isn’t functioning correctly, the body’s ability to fight off infections, heal wounds, and protect itself from serious diseases like cancer is diminished.
Research shows that sleep is one of the most important factors in enhancing the immune system, and in turn, a healthy immune system enhances our quality of sleep.
When this symbiotic relationship between sleep and immunity is disrupted, the risk of inflammatory and infectious diseases increases significantly.
Short-term lack of sleep might not seem like a big deal, but just one sleepless night can leave us vulnerable to viral infections like colds and flu. And a chronic lack of sleep due to a hectic lifestyle or insomnia can lead to much more serious, even life-threatening diseases.
4. Improved Sleep Means Improved Health
The research above is just the tip of the iceberg when it comes to the importance of sleep. But if you’re struggling with insomnia, there are many things you can do to avoid long-term issues.
Simple environmental tweaks and sleep hygiene strategies can work wonders, and there are plenty of natural and effective tools out there that can help.
So, why not make sleep a priority, and begin your journey to becoming a healthier, happier, and more vibrant version of yourself?
Conclusion
Hopefully, this post has helped explain the processes that happen when you fall asleep.
Sleep is a mysterious thing. Every living creature does it, but there are still many unanswered questions about why and how it occurs.
However, one thing we know for sure is that in order to be healthy and happy, we all need a good night’s sleep.
