I spend a lot of time thinking about sleep. Mostly because I am usually in bed unable to sleep and wishing I was asleep or at work being really tired and wishing I was asleep. I feel like I often don’t get enough sleep and it’s something that panics me because it triggers my vertigo.
I was thinking one evening last week as I was brushing my teeth about how sleeping is weird. That we all just shut down for a few hours every night. It’s weird.
I know sleep is important. It’s good for helping you heal, recover and repair. It’s also brilliant at curing hangovers. But I don’t really know why it’s good for you. My understanding of sleep is a bit vague.
Because of this, I thought I’d try to learn a bit more about sleep and then write a post about it.
What is sleep?
Sleep is a condition of body and mind which typically recurs for several hours every night, in which the nervous system is inactive, the eyes closed, the postural muscles relaxed, and consciousness practically suspended.
So the first thing I discovered is that people used to think sleep was a passive thing where your mind and body shut-down’. Had a bit of peace and quiet before the next day. But sleep is not passive at all. It is an active and dynamic physiological process, essential for our normal motor and cognitive function.
Back in the olden days, nobody really knew what triggered sleep. There were lots of theories about but they all seem a bit silly to me. One about a sleep toxin that builds up during the day and makes you tired at night, and other weird things like that.
In the 1980s, Alexander Borbély put forward the idea of the sleep-wake cycle. This cycle is regulated by two separate biological mechanisms in the body, which interact together and balance each other.
The two processes are:
- circadian rhythm: the regulation of the body’s internal processes and alertness levels (including the circadian drive for arousal and circadian alerting system), which is governed by the internal biological or circadian clock.
- sleep-wake homeostasis the accumulation of hypnogenic (sleep-inducing) substances in the brain, which generates a homeostatic sleep drive.
These processes are influenced both by our genes and our lifestyle. The body’s built-in circadian clock is the main mechanism that controls the timing of sleep and is independent of the amount of preceding sleep or wakefulness. This internal clock is coordinated with the day-night / light-dark cycle over a 24-hour period and regulates the body’s sleep patterns, feeding patterns, core body temperature, brain wave activity, cell regeneration, hormone production, and other biological activities. Even a long sleep might be ineffective if it occurs at the “wrong” time of the circadian cycle.
Human Biological Clock From Wikipedia.
Sleep-wake homeostasis is an internal biochemical system that operates as a kind of timer or counter, generating a pressure to sleep and regulating sleep intensity. Basically, it reminds the body that it needs to sleep after a certain time, and it works quite intuitively: the longer we have been awake, the stronger the desire and need to sleep becomes, and the more the likelihood of falling asleep increases; the longer we have been asleep, the more the pressure to sleep dissipates, and the more the likelihood of awakening increases.
These are just the two main processes at work, but there are other processes too, such as the suppression and re-activation of the everyday alertness signals of wakefulness, the switching between non-REM and REM sleep, the sleep inertia effect on waking, etc.
Genetics determine how much sleep we need, but adults need an average of 8 hours sleep. Some people need more, some less. If you are alert and able to complete all your daily tasks, then you are getting enough sleep. It’s thought we are getting much less sleep than we used to thanks electricity, technology and living in a 24-hour world. Babies need more sleep, obviously. As they have not developed their circadian clock yet, they sleep in blocks of around 4 hours and wake up for feed times.
What happens if we don’t get enough sleep?
Not getting enough sleep can lead to sleep debt. This causes mental, emotional and physical fatigue, problems in effectively performing day-to-day activities, impaired judgment and reduced alertness.
Not getting enough sleep has a serious effect on our mood – we can’t handle stress as easily, find it hard to concentrate, we become more forgetful, have mood swings, struggle to multitask, have lower body temperature, higher blood pressure and we can become more aggressive.
It can also have physical effects, such as increased risk of obesity, type II diabetes, fibromyalgia, psychosis, depression, bipolar disorder, stroke, heart attack, impaired immune function, and high blood pressure, among others.
Those who get enough sleep are thought to actually live longer than those who don’t!