Morning
Morning light sets the hour you get sleepy at night. How much you need, why it has to be early, and what to do when the sky is grey.
Ten minutes outside in the morning will change your evening. You'll get sleepy at a decent hour without trying, and the next morning is gonna be easier.
This is because your body sets its clock by the light it sees early in the day. It turns out that a few minutes outside in the morning is enough to get that clock going.
Lux tells you how bright the light is. A well-lit kitchen gives you 300 to 500 lux. Step outside on a grey, drizzling morning and that jumps to several thousand. On a bright morning, it can reach 100,000. Your eyes adjust, so the kitchen may look bright enough. But your body clock is harder to fool. To it, 500 lux still looks like dusk.
That first bright light helps decide when you get sleepy in the evening. It also has a say in when you feel hungry and when your brain feels properly awake.
A week in a tent
Researchers followed 8 people through an ordinary week at home, with the lamps and the screens and all the rest of it. During the first 2 hours after they woke, the light around them averaged 934 lux. Then they spent a week camping in the Rocky Mountains. Their light came from the sun and a campfire, and the morning average rose to 3,074 lux.
By the end of that week, their body clocks had moved about 2 hours earlier. The night owls moved the most. They went to bed whenever they felt like it, and their body clocks still shifted with the daylight.
To your body clock, a bright kitchen still looks like dusk.
Outside, and early
Through a window, you see only a patch of sky, and the glass cuts the light further. Even a sunny seat indoors may give you only a few hundred lux. The pavement just beyond the glass gives you several thousand. Step outside and you get the whole sky.
The timing matters too. Get outside within the first hour after you wake, and you should feel sleepy at a decent hour that night. You can keep the afternoon walk. It is lovely, but it does a different job.
| Roughly | What to do | |
|---|---|---|
| A well-lit kitchen | 300 to 500 lux | Go outside if you can |
| A sunny seat behind glass | A few hundred lux | Give it 30 minutes or more when you cannot get outside |
| At home in the study | 934 lux | The average for the first 2 hours awake |
| Camping in the study | 3,074 lux | The average for the first 2 hours awake |
| Outdoors, grey and drizzling | Several thousand lux | 20 to 30 minutes |
| Outdoors, a bright morning | Up to 100,000 lux | 10 minutes |
How to get it
- 10 minutes outside in the first hour after waking, before the phone. The garden, the front step, the walk to the end of the street.
- 20 to 30 minutes when it is grey. A cloudy sky still gives you thousands of lux, so winter mornings work. They only take longer.
- Make it part of something you already do. Drink your coffee outside, take the dog out earlier or get off one stop early and walk.
- Eat afterwards. Meals help set your clock too, although light has the stronger say. Get outside, then have breakfast.
- In midwinter, take the first daylight you can get. In New York in December the sun is barely up before half past seven, so the light is waiting on the way to work.
- Open the window when you cannot go outside. Sit as close to it as you can, and give it longer.
- Keep the evening lights low and the bedroom properly dark. Morning light and a dark night work as a pair.
Try it for a week or two. Chances are, you will start getting sleepy at a decent hour and waking up more easily.
Good hotels sell this back to us as breakfast on a terrace and a swim before anything else. It is the same light that will be outside your door tomorrow morning.
The short answers
What people usually want to know.
How much morning sunlight do you need?
Ten minutes outside in the first hour after waking, and 20 to 30 minutes when the sky is grey. Before the phone, if you can manage it.
Does it have to be outside, or is a window enough?
Outside. Through a window, you see only a patch of sky, and the glass cuts the light further. If you cannot go out, open the window, sit close to it and give it longer.
Does it work on a cloudy day?
Yes. An overcast, drizzling morning still gives you several thousand lux, far more than a room indoors. Winter mornings work. They only take longer.
Why does it have to be the morning?
Light in the first hour after waking pulls your clock earlier, which helps you get sleepy at a reasonable time that night. An afternoon walk is lovely, but it does a different job.
How much brighter is outdoors than a bright room?
A well-lit kitchen gives 300 to 500 lux. In the camping study, the light around people averaged 934 lux during the first 2 hours after waking. At camp, it averaged 3,074 lux. A bright morning can reach 100,000 lux.
What does morning light actually change?
The first bright light helps decide when you get sleepy in the evening. The same clock helps time your hunger and the hours when you think most clearly.
What did the camping study find?
Researchers followed 8 people through an ordinary week at home, then through a week of camping with sunlight and a campfire. Their body clocks moved about 2 hours earlier, and the night owls moved the most. Everyone chose when to sleep, so the daylight did the work.
What can you do on a dark winter morning?
Take the first daylight you can get, even if that is on the way to work. In New York in December the sun is barely up before half past seven, so the light is waiting on the commute rather than at home.
Does breakfast help set the clock too?
Meals help set your clock too, although light has the stronger say. Go outside first and eat afterwards.
What else has to happen for it to work?
Keep the evening lights low and the bedroom properly dark. Morning light and a dark night work as a pair.
How long before you notice a difference?
Try it for a week or two. You may notice that you get sleepy at a reasonable hour and wake more easily the next morning.
The studies. Wright KP Jr, McHill AW, Birks BR, Griffin BR, Rusterholz T, Chinoy ED. "Entrainment of the human circadian clock to the natural light-dark cycle." Current Biology, 2013;23(16):1554-1558. Eight adults received more than 4 times as much light across the day while camping. During their first 2 hours awake, average exposure rose from 934 to 3,074 lux. After the camping week, their bodies began producing melatonin about 2 hours earlier, and their clocks moved into line with sunset and sunrise. Read the full study · PMID 23910656 · doi:10.1016/j.cub.2013.06.039.
St Hilaire MA, Gooley JJ, Khalsa SB, et al. "Human phase response curve to a 1 h pulse of bright white light." The Journal of Physiology, 2012;590(13):3035-3045. In a controlled study, 18 people received 1 hour of light at about 8,000 lux and 18 received dim light. The direction and size of the shift depended on when the light reached them. Read the full study · PMID 22547633 · doi:10.1113/jphysiol.2012.227892.
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