We are often guilty of thinking of sleep in isolation but, in fact, it’s part of a 24 hour (circadian) wake-sleep cycle or rhythm.
Exposure to light is its most powerful regulator, the so-called zeitgeber, regulated by the suprachiasmatic nucleus. Getting sufficient light shortly after waking and during the day is really important in regulating our sleep/wake cycle and quality of both our alert times, and sleep.
So, too, is the consistency of our routine, including the time we get up, the time we go to bed, our exercise and our nutrition.
Things you can do
Be consistent
One of the most powerful things we can do to support our sleep is to get up at the same time every day, including on weekends. In fact, being in sync with our circadian rhythm is thought to be as important as the amount of sleep that we get.
When you choose to get up will depend on the constraints of your life, your work and the people in it, and also your genetic chronotype, which is the time of day that you naturally are almost alert and want to sleep. You can do a free chronotype assessment, below.
Try out having consistent wake and sleep times every day for the next 2 weeks, including weekends, and see what impact it has on your sleep.
It can be helpful to, in addition to your morning alarm clock, consider adding ‘digital shutdown’ and ‘bedtime’ alarms, to support this.
Light hitting our retinas tells us what time it is – it is our main Zeitgeber or ‘time giver’.
Exposure to light is particularly important in the hour after waking, to support our cortisol surge. A circadian timer is set when the cortisol pulse occurs, 12-14 hours or so after which, melatonin is released, supporting sleep.
Figure: 12-14 hours after our cortisol surge, melatonin is released.
Andrew Huberman recommends aiming for 100K lux in the hour after waking.
‘Lux’ is a measure of how bright the light we are exposed to is. Broadly speaking, natural light is brighter than artificial light so, if you can, get outside* within the hour after waking for at least:
Bright cloudless days – 5-10 mins
Cloudy - 10-20 mins
Overcast – 30 mins
This might be to drink your morning drink or eat breakfast, go for a walk outside, or on your way to work. Because the aim of the game is light hitting your retinas, avoid sunglasses or shading hats.
If you can’t get outside, you can use light boxes or clocks, visors or glasses that you can wear or sit in front of. You can assess the brightness of the light in your environment using a photon meter.
Light during the day is also important. 87% of the time, we are inside, so consider having lunch outside, walking meetings, or light boxes on your desk.
*Never look directly at the sun, and be careful about sun protection for your skin.
Exercise or movement is another way to tell our brains that it's time for action, and support our morning cortisol surge, which occurs shortly after waking as part of our stress response. 12-14 hours after this morning cortisol surge, melatonin is released, to support our sleep.
Figure: 12-14 hours after our cortisol surge, melatonin is released.
Think back to your evolutionary past. You would know that it was time for sleep partly because you would likely have a tired body to match your tired brain. It is a strange thing that we experience in our current culture where our mind is tired but our body is not, so we end up wired but tired.
Having said that, try to avoid vigorous exercise too close to bedtime unless you can cool down afterwards. Listen to advice around exercising at bedtime with our Expert Conversation for sleep, timestamp 42.50.
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