Today's world is a world of late night TV (or streamed laptop tv if that's your thing) and bright lights at the flick of a switch that make it easy to forget that for thousands of years we lived in sync with the light and dark cycles of day and night. Our physiology is still the same as our ancestors who's very lifestyles were driven by the sun. The main difference now is we have many ways to add gadget filled, artificially lit, 24 hour a day stimulation to our lives; yet, we are still unable to completely escape the basic need to sleep when it's dark and wake up when it gets light. We can fight these drives on a short-term basis but will eventually have to return to this basic rhythm, or suffer ill health as a consequence.
What is the circadian cycle?
The circadian clock (or cycle) affects the daily rhythms of many physiological processes. Circadian rhythms tend to be synchronised with cycles of light and dark. Other factors such as ambient temperature, meal times, stress and exercise can influence the timing as well. You'll probably recognise a lot of your own 'habits' are naturally inclined towards these times of day.
Whenever light stimulates our eyes and/or skin the brain and hormonal system thinks it's morning. In response to light the hormonal system naturally releases cortisol. Cortisol is a hormone released in response to stress - light being a form of electromagnetic stress. This cortisol activates the body and prepares it for movement, work, combat, or whatever may be necessary for its survival.
Cortisol levels peak between 6am and 9am, then drop a little but remain high through midday to support daily activities. In the afternoon cortisol levels begin dropping significantly, especially as the sun goes down. These decreasing cortisol levels allow the release of melatonin (hormone-like effect secreted from the endocrine system) and increase the levels of growth and repair hormones.
What's happening during sleep time?
Following these natural cycles we should fall asleep by about 10pm most nights. Physical repair mostly take place when we're asleep between the hours of 10pm and 2am. Between 2am and 6am the immune and repair energies are more focused on psychological repair. If you are someone who exercises regularly and also has work/life mental stress getting a full nights sleep is imperative to avoiding inhibited function or even breakdown.
REM sleep - What exactly happens when you're asleep?
When we finally fall asleep we go through approximately (and ideally) five 90 minute sleep cycles. REM (rapid eye movement) sleep occurs 90 minutes after the onset of sleep. The first period of REM typically lasts 10 minutes, with each recurring REM stage lengthening, and the final one may last up to an hour (shown in the lower diagram).
Polysomnograms show brainwave patterns in REM to be similar to that recorded during wakefulness. In most people heart rate and respiration speed up and become erratic during REM sleep. During this stage the eyes move rapidly in different directions. Intense dreaming can occur during REM sleep as a result of heightened brain activity.
To awaken refreshed we should ideally awake during the final stage of non-REM sleep. If we awake during a deep sleep cycle this can lead to disorientation and grogginess for an extended period.
8 Tips to improve your sleep immediately
Get into bed by 10pm
- this should be done after a 'wind down' period before you go to bed. The goal is to get into bed by this time and fall asleep within 15 mins. Reading etc. should be done during the wind down period, not in bed.
Develop a wind down period before bed
- within 1-2 hours of going to bed dim lights in the house and avoid T.V or computer screens. This time should allow your body to get ready for sleep.
Condition yourself to fall asleep
- having a regular bedtime and wind down period should allow your body to learn that when it gets into bed it's time to sleep. Much like when you do a movement prep warm up, it's time to exercise.
Remove electromagnetic pollution
- where possible remove any electrical pollution from your immediate sleeping area. Clocks, phones, laptops and other things that go beep should be in another room, or located far away from you in your bedroom.
Ensure your room is completely dark
- with what you now know about our relationship to light, make sure you have affective curtains which fully block light, and also no artificial lights (or gadgets as above) left on the room while sleeping.
- if you have a tendency towards trouble sleeping avoid caffeine, sugar and nicotine (and any other stimulants) from after lunchtime.
Drink plenty of water
- when dehydrated the body responds as if it's experiencing stress, and if it thinks it's stressed it will produce stress hormones, which are our awakening hormones.
Lastly and most importantly exercise regularly
- it is significantly harder to stay awake too late if you are physically fatigued. The best way to ensure your lights go out at the right time is to exercise with suitable intensity and regularity, which will help to naturally prepare you for sleep. Just be careful with late evening exercise as this can disrupt the ideal sleep pattern by raising cortisol levels.