Our world is very different to that of our ancestors who had no clocks or electricity. They woke when the sun came up and went to sleep when it set. Today, we often get up when our alarm clock rings and go to bed long after the sun has set. When our natural sleep cycle is broken, what effect does this have on our bodies? Research seems to show that the constant tug-of-war between our external and internal clocks definitely does have an effect on them.
What is a sleep cycle?
Your eyes are light sensitive and your brain responds to the signals they send. Your brain regulates body temperature, eating patterns, when to sleep and rise and even hormones according to these signals. This is referred to as your ‘body clock’ or circadian rhythm. The word circadian comes from the Latin word ‘circa’ that means ‘around’ or ‘about’ and ‘diem’ that means day. A sleep cycle of roughly 24 hours co-ordinates with the light-dark cycle of the earth. Sleep cycles differ from person to person and also depend upon age. A child, adolescent and adult all have different sleep cycles.
Stages of sleep
Your sleep cycle begins with non-REM sleep, made up of 3 stages, each one of which can last for about 5 to 15 minutes. Once you have completed this cycle, you enter Rapid Eye Movement (REM) sleep before the cycle starts all over again. Most non-REM sleep happens early on in the night and the length of REM periods increases as the night goes on.
When you nod off, brain wave activity gradually starts to slow down. Your eyes roll around and may open and close from time to time. You are sleeping so lightly that you can easily be woken up.
In this stage muscle activity decreases and conscious awareness of the outside world begins to fade completely. Dreaming is rare but twitches are quite common, often accompanied by a falling sensation. The brain starts to emit larger waves.
Did you know?
More time (45 to 50% of total sleep time) is spent in stage 2 sleep than any other stage.
This stage consists of what was previously known as stage 3 and stage 4. Your brain starts producing slower delta waves. It becomes harder for you to wake up because you are responding less to outside stimuli. Eye and muscle movement stops. Heart rate, blood pressure, breathing rate and brain temperature are at their lowest levels in this stage. Dreaming is more common during this stage than the other non-REM sleep stages but not as common as during REM sleep.
In this stage tissue growth and repair occurs, energy is restored and hormones are released. These hormones are essential for growth and development.
Did you know?
Other names for this stage include “slow-wave sleep” and “Delta sleep.”
You usually enter Rapid Eye Movement (REM) Sleep about 90 minutes after falling asleep. Each REM stage can last up to an hour. You may go through five or six of these cycles every night. In this final phase, your brain is more active. Your eyes jerk quickly, your heart rate and blood pressure increase. Your breathing is fast and shallow and you dream most in this phase. The brain waves you emit at this stage look a lot like those recorded when you are fully awake. Another paradox of this phase is that even though your brain is very active, your muscles are paralyzed and unresponsive.
During REM sleep, your brain replenishes neurotransmitters. This is essential for problem solving, learning and remembering. The images and information you receive during the day are processed and stored in your long term memory.
Did you know?
The average adult only spends about 20% (1.5 hours) of eight hours of sleep in REM sleep.
When your sleep cycle is disrupted
If sleep is disrupted, the sleep cycle is reset and may cause you to miss time in the final stages. If you do not experience REM sleep for even one night, your body may go directly into REM sleep the next night until you ‘catch up’. Waking up to an alarm clock means that you might wake up in the wrong stage of the sleep cycle. If you wake up in stage three you will probably feel as though you have had hardly any sleep. When you suffer from a sleep disorder or are woken up frequently, your body is often not able to move into deep sleep and REM sleep.
Effects of living against your natural clock
The discrepancy between internal time and external time affects everyone, from children to those of retirement age. We use alarm clocks to wake up in the morning and then try to make up for lost sleep on weekends. We tend to spend too much time indoors, stay up too late, and use caffeine and sugar to give us energy.
At first scientists studying this discrepancy between internal and external time focused on night-shift workers and others whose jobs meant that they suffered the most disruption to their sleep-wake patterns. However, now research appears to be showing that it is not only these people whose bodies are affected. As long as our sleep cycle is controlled by external rather than internal factors, we are not at our best mentally or physically. Exposure to so much unnatural light and waking up with alarms seems to be extracting a toll on our bodies.
In 2012, a large scale study by Till Roenneberg and his team at Ludwig-Maximilian University found that the conflict between circadian and social clocks resulted in chronic sleep loss. They saw a link between sleep disruption (which they called ‘social jet lag’) and increased BMI. Their results reflected that living “against the clock” may be a factor contributing to obesity.
In 2015, a study at University of Pittsburgh also revealed a link between disruption in sleep cycles and known metabolic risk factors for obesity, diabetes, and cardiovascular diseases. It was found that chronic disruption of circadian rhythms could contribute to metabolic imbalances that cause glucose intolerance and obesity.
Major neurodegenerative diseases like Parkinson’s and Alzheimer’s may also be connected to disrupted circadian rhythms. Findings of a recent study suggested that poor sleep, of a fragmented or short duration in older adults, could cause a disrupted circadian rhythm. This in turn, lead to increased accumulation of toxic beta-amyloid proteins – a known precurser of Alzheimer’s.
Tips to help you get a good night’s sleep
Here are a few tips to help you increase your chances of a good night’s sleep:
- Keep a regular sleep schedule. Our bodies respond well to consistency. It means that our bodily systems are able to prepare in advance. Our digestive systems become activated in advance of regular meal times so we can process are food. We begin to feel sleepy prior to our bedtime.
- Create a relaxing bedtime routine. Surfing the internet or watching TV from your bed is not a good idea. These devices emit light and receiving too much light at night can make it harder for you to fall asleep. Listening to music is relaxing. Learning some breathing exercises may be very helpful when you are battling insomnia. A spiritual activity like praying is also a good way of handing over any worries and feeling peaceful. If you find that breathing exercises do not really work for you, it’s worth trying a sleep device called 2breathe. It helps you to breathe yourself to sleep when you don’t know how to meditate or empty your mind.
- Stay away from big meals at night. Eating late at night, especially if you eat heavy foods, is a recipe for acid reflux which can keep you awake.
- Avoid alcohol before bed. Drinking alcohol before bed might help you fall asleep faster but research shows that you quality of sleep is poorer. It seems to lead to warring alpha delta patterns which is disruptive to sleep.
- Pick up on your body’s natural cues. Your body tells you when it needs sleep and you need to listen to its cues rather than ignoring them by staying up and watching TV.
- Expose yourself to sunlight. Just as you need to be in the dark at night, you need to be in the sunlight during the day. Exposing yourself to sunlight a few times a day helps to reset your sleep cycle and also increases vitamin D production.
- Make sure that you are warm or cool enough. Temperature is often overlooked as a factor preventing sleep. Open windows to clear out any hot, stuffy air. A cool shower before bedtime is better than a hot bath as it takes the body a long time to cool down.
- Don’t just lie in bed for hours feeling more and more frustrated. It should usually take about 20 minutes to fall asleep. If you have been lying awake for much longer than that, get up and go through your relaxation routine again.
James B. Maas, PhD, and author of the best-seller Power Sleep says “Most adults are moderately to severely sleep deprived, and it affects their productivity, their work and their relationships. If we treated machines like we treat the human body, we would be accused of reckless endangerment.” In his book, this pioneer of sleep research at Cornell University, has created an easy, drug-free programme to improve your body and mind.
The quality of our sleep, not necessarily the quantity, affects how we feel and perform on a daily basis. When sleep is cut short, muscle repair, memory consolidation and release of hormones regulating growth and appetite are affected. We need to do whatever it takes to make sure that we have enough good quality sleep.