Part 1 - Sleep cycles
We all need it. Try asking new parents about their sleep quality when a new baby arrives, I bet most of them will look at you through dreary eyes and a veiled smile. ‘Don’t worry we’ll catch up when baby gets into his/her routine’. This is a common misconception: sleep time can’t be regained once lost (1).
Sleep patterns have changed through history. People used to manage a good night’s sleep, today it is estimated 1 in 2 adults are getting less than 6 hours (1).
Sleep is so important for so many functions:
Appetite and weight control
Blood pressure control
Normal sleep comprises 90-minute cycles. Each cycle comprises two kinds of sleep: NREM sleep (non-rapid eye movement sleep); followed by REM (rapid eye movement) sleep. Deep sleep happens towards the end of each cycle.
So briefly, the brain needs rest to repair adequately and we need 4 or 5 cycles to feel the benefit. NREM sleep should be dominant in the early part of sleep, this is where the brain identifies and removes unnecessary neural connections and collates memories, a sort of an emotional filing. It also promotes tissue repair and renewal (releasing growth hormone) and there is greater immune activity.
REM is more dominant in the hours before waking. It is very necessary to restore the mind, so this is when new neural connections are strengthened and created, using the space freed up by NREM sleep. Waking up too early shortens REM sleep by 60-90%. During REM sleep nor-adrenaline is blocked from the brain, which allows the brain to be in a parasympathetic nervous state allowing the ‘decommissioning’ of emotional upset that might be related to previous traumas. Dreaming.
The body works on an internal clock, known as the circadian rhythm (wake/sleep cycle) which exerts control over many body processes. The cycle is different between individuals, some may be morning people, some evening and others in the middle.
In our 24/7 world we seem to have forgotten the importance of getting a good Z’s. More and more people seem to be living at a frantic pace, our lifestyles have us getting up early to commute to work, often returning late, eating dinner and then off to bed in the hope of getting a good night’s sleep. Does that ring any bells?
Continued in Part 2 – Lack of sleep: a driver for adverse health conditions (see next week’s post).
Walker M (2017). Why We Sleep. The New Science of Sleep and Dreams. Penguin Books.