Our organs are programmed to function in cycles of 24 hours. This is called the circadian rhythm or sleep-wake cycle. How do our organs know where we are in the 24 hour cycle? By detecting and releasing certain hormones and neurotransmitters at different times during the cycle. The main hormones involved are cortisol, a steroid hormone released by the adrenal gland which typically peaks first this in the morning signalling to our organs the beginning of the day, melatonin, a hormone released primarily by the pineal gland at night which signals the end of the day. There are other signaling mechanisms involved such as the accumulation of adenosine activity in the brain which is a neurotransmitter that once accumulates at night helps us fall asleep.
When these hormones and neurotransmitters are out of sync with each other and/or the time of day they should normally correlate with, this is what I mean by the circadian rhythm being out of sync and may be in need of “resetting”.
What does a circadian rhythm that is functioning optimally look like?
Waking up at the same time in the morning feeling refreshed.
Feeling energised throughout the day (not feeling the need to nap during the day)
Gradually getting sleepy during the evening at the same time every day.
Falling asleep within less than 30 minutes of getting into bed.
Staying asleep and not waking up during the night.
Signs that our circadian rhythm is ‘out of sync’ that can be seen on sleep wearables:
Low percentage of deep sleep due to the scarcity of signals helping us move from light sleep to deep sleep.
Not getting enough REM sleep: This can be due to waking up ‘too early’ in the morning before getting enough sleep. Normal sleep happens in cycles of approximately 90 minutes. REM sleep is a stage of sleep which occurs at the end of each cycle. The percentage of REM of each cycle increases towards the end of the night. If we wake up ‘too early’ our REM sleep can be suboptimal.
Resetting your circadian rhythm
There are practical steps we can take to ‘reset’ our circadian rhythm throughout the day.
1. In the morning
Wake up at the same time: set a time to wake up and try to stick to it every day. With consistency, you will gradually set your circadian rhythm to start at this time every day. Ideally, try to avoid traditional alarms but if necessary, use waking up lights or gentle alarm sounds to wake up in the morning (such as Sleep Cycle app). Traditional alarms have been shown to cause an unnecessary increase in heart rate and blood pressure at waking up.
Get some daylight first thing: try to get 15-30 minutes of exposure to daylight by taking a walk outside (not through a window). The aim is to get exposed to a light source with more than 10,000 lux (a measure of light intensity). It is very difficult to get this from an electrical light source. If you’re not able to get daylight then a bright indoor light that emits >1000 lux might be helpful. The aim here is to stimulate the photoreceptors in our eyes which can help cortisol release.
Try to get regular daylight exposure throughout the day to help reinforce the day and night cycle.
2. In the evening:
Eating: try to avoid eating (especially carb heavy meals) 3 hours before going to bed. However, Some foods have been shown to increase melatonin and serotonin levels such as sweet cherries and kiwis. These can help us fall asleep better.
Screens: set all phones, tablets and monitors to night mode (set to highest setting possible). If the screen has no night mode such as some TV screens then try to avoid or use blue light blocking glasses. Always use dark mode on all applications and browsers and decrease screen brightness to the lowest setting possible. The aim here is to minimise the effect of blue light on melatonin release at night.
Lighting: turn off or dim all lights in your household. Only use low orange lighting (artificial candle lighting or dim lamps)
Caffeine: do not consume coffee, black tea, green tea, dark chocolate or any source of caffeine after noon. The reason is that caffeine has a long half-life (approximately 5 hours). This means that 10 hours after caffeine ingestion, we can still have 25% of the caffeine we consumed circulating in our bloodstream. Caffeine directly blocks the effects of Adenosine which is one of the main neurotransmitters involved in our sleep-wake cycle.
Do not do any vigorous exercise late in the evening. The idea here is to avoid release of cortisol which increases when putting our bodies under stress. We want there to be a distinct pattern of high cortisol in the morning and low cortisol in the evening. Try to get your exercise in the morning or afternoon.
There is some weak evidence that using an earthing sleep pad may help with melatonin release at night and hence help reset your sleep-wake cycle.
3. At night when going to bed
Light: blackout your room. Use blackout blinds or curtains (available on Amazon and are easy to install). Make sure that no light enters the room especially during the early morning when the sun starts to rise. Use a comfortable eye mask that covers the entire visual field if the room is not completely dark. Cover any sources of light from electronics in the bedroom.
Noise: make sure that noise is minimal especially early in the morning. Consider comfortable earplugs if you cannot control noise (or if you have a noisy partner!).
Some supplements may help such as melatonin. We’ve covered the topic of melatonin before. Make sure to consult your healthcare professional for more information on what supplement is right for you.
Dealing with jet lag
If you have severe jet lag or if your intended sleep time is more than 2-3 hours off your desired sleep time, gradually move your waking up time one hour each day towards your desired waking up time until you reach your desired schedule. You need to maintain this for a few weeks before you cement the new schedule in place.