Circadian Disruption

Circadian Disruption

You’ve likely heard about the importance of sleep duration, and how seven hours is vital for general wellbeing. You’ll also probably have read stuff about circadian rhythms too. But what about circadian disruption?

The term refers to the disturbance of biological timing, essentially of having an irregular sleep schedule. One science paper refers to it as the “internal manifestation of the solar day.” The research around the benefits of maintaining a consistent wake time is truly remarkable -- and have only recently been properly discussed.

To briefly explain, our circadian rhythm is what guides our master clock. It’s chiefly triggered by light exposure. In wildly oversimplified terms, when it’s bright out, we’re switched on and active; when it’s dark, we should slow down and recover for the next day.

Why You Should Care

Humans are built to run on a (roughly) 24-hour cycle. Studies have shown that even when we live in caves or bunkers, without light or temperature cues, we’ll maintain sleep-wake and body temperature rhythms without any external stimulus. But that’s when we have no choice but to listen to our bodies…

It’s easy to forget that it was only around a century ago when electric lights entered our homes. Only 6% of UK homes had electricity in 1919. This jumped to 66% by 1939.

This transformative ability to control lighting has brought with it unprecedented flexibility. Contrastingly, it’s introduced the possibility of circadian disruption which, prior to 100 years ago, was incredibly rare.

Regularity Over Duration

2023 research compiling 10 million hours of data from 60,000 UK participants unveiled some truly chilling figures. When comparing the top 80% of sleep regularity scores with the bottom 20%, they found a:

20-48% lower risk of all-cause mortality.
39% lower risk of cancer mortality.
22-57% lower risk of cardiometabolic mortality.

What’s more, the researchers concluded that “sleep regularity was a stronger predictor of all-cause mortality than sleep duration.”

Whilst the anointed seven hours per night is definitely a target, there’s another thing to consider if you’re aiming to optimise your sleep.

Circadian disruption does more than just impact your physical. One meta-analysis of 11 studies found a 40% increase in depression when comparing night shift workers to daytime workers.

Social Jet Lag

Of course, we all have different things going on that cause us to have altered sleep cycles from time to time. This is satisfyingly known as social jetlag and refers to the additional sleep we seek on non-workdays compared to "school nights."

Irrespective of what you do in the evening, the key to avoiding circadian disruption and the countless ailments that arise following it is to wake up at the same time each day as much as possible. The time we rise is what triggers our circadian master clock, so maintaining regularity with that time is the holy grail to benefit from all the words in this email.


If you were waiting for a piece of this email to give you a bit of leeway, you’ve arrived at the right part. The consensus from sleep experts is that adding an extra hour to your sleep when you can fit it in is still viable if you’re looking to optimise your sleep schedule.

So no, not 06:30 every morning… Just most of them.

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