How to sleep better – circadian rhythm, sleep pressure, light and caffeine

A thorough walk through what actually affects your sleep – and what you can do about it.

The starting point is personal: Jan Sindre struggled to fall asleep for a period, read up on it, and worked methodically through the advice in Matthew Walker’s book. The solution turned out in the end to be something he had not considered at all.

The episode is built on what Matthew Walker, Andrew Huberman and Bryan Johnson agree on – not on what they disagree about. Everything is explained with the Norwegian conditions in mind: the dark season in winter and the bright nights in summer.

The two systems everything else rests on

Nearly every piece of sleep advice you hear works through one of two systems. Grasp which one, and you also understand why the advice is given – and what happens when you break it.

Circadian rhythm and sleep pressure

System 1

The circadian rhythm

• The body clock that tells you where in the day you are
• Set first and foremost by light
• Melatonin belongs here – the signal that evening has come
• That is why morning light works, and why a fixed wake-up time counts for more than a fixed bedtime

System 2

Sleep pressure

• How long it is since you last slept
• Builds through the whole day, as adenosine
• Reset when you sleep – and partly by a long afternoon nap
• That is why caffeine works: it gets in the way of the adenosine signal without removing the pressure

Why the afternoon coffee counts

Caffeine has a half-life of five to six hours. That does not mean the effect is over by then – it means half of it is still there.

One cup of coffee at 3pm

The day that hangs together

Light is the strongest single factor you control yourself, and it works in both directions: plenty of light early helps, plenty of light late hurts.

Melatonin through the evening

It is also why indoor light and daylight are not the same thing. Outdoors is many times brighter than indoors even on a grey day, and that difference is what the body responds to – not whether a lamp feels bright.

Four links, in order

1. 1A fixed wake-up timeThe same hour every day, weekends included. This is the link that holds the rest in place.
2. 2Light earlyGet outside into daylight as early as you can. In winter even a grey day counts for more than indoor lighting does.
3. 3A caffeine cut-offSet a limit in the middle of the day and keep it. The difference shows up in the evening.
4. 4An hour of winding downDimmed light, a lower gear, no screen right before. You do not go from a hundred to zero in a minute.

↻ And then it begins again the next morning

Your resting pulse in the hour before bed tells you whether the body has actually wound down.

What keeps it up: hard training late, a large meal, alcohol, nicotine, caffeine, stress and a room that is too warm. If your pulse is noticeably above what is normal for you as you go to bed, the body is still working – and you will sleep worse even though you feel tired. This is one of the few things you can measure yourself, with a watch or a ring, instead of guessing.

Alcohol makes you fall asleep faster, but sleep worse.

Why this confuses people: falling asleep is the part you notice. What happens through the rest of the night – broken sleep and less dream sleep – is the part you are not awake enough to register. That is why it feels as though it works.

The content is general knowledge based on the sources listed, not individual health advice. If you have persistent trouble sleeping, contact your doctor.

Main topics

• The circadian rhythm and the body clock
• Sleep pressure and adenosine
• Melatonin and light
• Caffeine and its half-life
• Morning light and daylight
• An evening routine and winding down
• The bedroom - dark, cool and quiet
• Alcohol, nicotine and meals
• Sleeping through a Norwegian winter and bright summer nights

Questions this episode answers

• How can I sleep better?
• What is the difference between melatonin and adenosine?
• How long does caffeine stay in the body?
• What time of day should I stop drinking coffee?
• Why does a fixed wake-up time matter more than a fixed bedtime?
• What do I do the day after a bad night?
• How cold should the bedroom be?
• Does alcohol help you sleep?
• What do I do when I am lying awake and cannot fall asleep?
• How do I get enough light during a Norwegian winter?

Key points

• Sleep is governed by two systems - the circadian rhythm and sleep pressure. Everything else builds on those.
• A fixed wake-up time matters more than a fixed bedtime.
• Caffeine has a half-life of five to six hours, and turns up in more than you think.
• The body needs about an hour to wind down - you do not go from a hundred to zero.
• Alcohol makes you fall asleep faster, but sleep worse.
• The bedroom should be dark, cool and quiet.

Sources and references

• Matthew Walker – Why We Sleep
• Andrew Huberman – Huberman Lab, the episode on sleep
• Bryan Johnson – work on sleep and optimisation