Types of sleep
There are two kinds of sleep; one is a deep deep sleep (non-rapid eye movement, or NREM) and one is a lighter dream-filled sleep (rapid eye movement, or REM). And NREM is divided into four stages of depth. The two types cycle throughout night; we do a bit of one then switch to the other, repeatedly, but we spend 75-80% in the deep stuff, if we are sleeping well.
We usually fall asleep and go into deep sleep straight away, after a few minutes of semi consciousness – a time when it’s easy to be woken by noise or disturbance. People who have a sleep disorder, such as narcolepsy, sometimes go straight into the lighter sleep and start dreaming right away or at least seeing images.
The four stages of deepness:
Stage 1 – 1-7 mins. Light and transient, easy to be woken.
Stage 2 – 10-25 mins. A bit deeper. It has patterns of brain activity called ‘sleep spindles’, which are thought to help us consolidate memories and to process information, as well as playing a part in emotional regulation.
Stages 3 and 4 – 20-40 mins. Stage 3 doesn’t actually last very long, it leads into the deepest stage 4 sleep. This is slow wave sleep and is when the brain gets its cleaning tools out and sends waste products down its rubbish chutes – the glymphatic system. Important processes, such growth and repair and immune system regulation, also take place during this time. Hence lack of sleep can mean poor growth in children, poor healing in adults and can be an invitation to disease and lack of recovery.
When we’re in the lighter sleep, the dream stage, our muscles become somewhat paralysed. This is thought to be in part to stop us fully acting out our dreams.
The lighter, dreamier, sleep – REM
This is a time of crazy brain activity and dreaming. One purpose of dreams is to aid problem solving and emotional processing – making sense of things that have happened during waking hours. In babies it’s important for brain development. The semi paralysis is also thought to allow restoration of muscles and tissue, while they’re not having to do much. It also creates an interlude between the deeper stages so that we don’t completely zonk out for hours on end and get eaten by a prowling lion.
As for nightmares, they can happen if we are going through stress, anxiety and trauma. Some people will experience a recurring nightmare that seems only to pop up when they are going through tough times. My own recurring nightmare has a water theme but the locations vary. Wherever I am starts filling hugely with sea water and I can’t get back to shore. Another one of mine is boarding a plane with a sense that it’s going to crash. I guess the brain selects your deepest real-life fears!
When we wake up we normally do so in response to increasing daylight, it’s a pretty strong mechanism. But it’s not just daylight; increasing levels of hormones such as cortisol help to pop us out of sleep, hence blood pressure is higher in the morning than at night (also why a lot of heart attacks take place just before waking because it’s when the system starts firing up).
There are also certain genes, *clock genes*, that act like wake and sleep switches, giving rise to daily patterns of activity that vary across bodily organs. Furthermore, a hormone called melatonin influences wakefulness and sleepiness, it increases towards bedtime, helps to keep us asleep, then diminishes in the morning and during the day – well, it’s supposed to… The problem is it reacts to light and other stimuli, so if we have the lights up bright in the evening or we are using screens melatonin production is suppressed and we can’t get to sleep as we should.
Body temperature plays a big part too, we are hotter when we’re awake and when we sleep we get cooler, and we need a cooler core temperature to induce sleep. This is why it’s good to have a hot bath before bed and to keep the bedroom cool (and dark during darkness hours, i.e. no LED alarm clock lights or phone screens).
All these mechanisms drive us toward waking up bright and bushy-tailed then gradually getting sleepier as the day progresses. With a good night’s sleep that works well but with a bad night’s sleep it all goes to cock and the mechs don’t work together efficiently.
Sleep through the age stages
Sleep patterns change with age. Anyone who says their newborn sleeps through the night every night is a bit suspect because babies are just not wired up that way and it’s quite bonkers to expect them to be. They’re wired up to sleep between 2.5-4hrs at a time, but they need loads of sleep, like 16hrs a day.
Teenagers need a ton of sleep as well, a good 10 hours. But they’re often sleep deprived these days due to social media in bed then having to get up for school or college. If you have one, or some, try to help them to go to sleep earlier while respecting they have teenage *things* to do. And let them lie in for ages at the weekend. It’s a physiological need.
As we get on in years we seem to need a bit less sleep. Hence why lots of elderly people get up at about 4:30am! But we still actually need a good solid 7hrs in old age, so you’ll notice they go to bed just after the 9 o’clock news. Note: Watching the news before bed can disrupt sleep!
Things that can help you to sleep better
- Eating dinner early and leaving a good few hours between the last food of the day and bed.
- Not drinking alcohol in the evening (and minimising it for the rest of the time).
- Not drinking caffeine in the afternoon or evening if you’re caffeine sensitive.
- Sauna – not very accessible to most people but has significant proven benefits to sleep and cardiovascular health.
- A hot bath or shower before bed.
- Low light in the evening. Not switching on a bright bathroom light just before getting into bed.
- Low level of screen use for an hour or two before bed, and even then having on a night setting (orange light).
- Low level of mental stimulation pre-bed. Not a good idea to watch the news!
- A cool bedroom with no artificial light pollution from alarm clocks or what have you.
- Managing stress and anxiety.
- Being a healthy weight in order to keep sleep apnoea at bay.
- Umm, sex!
I think I should end there…. But do watch this brilliant video.