Eating late, phones before bed and artificial light are disrupting your circadian rhythms
Ever spent the night staring, fixated, on the ceiling, followed by a day spent in a gauzy daze? Then the impact of an off-kilter circadian rhythm has been felt in your life. This – the 24 hour cycle which comprises your body’s ‘internal clock’ – directs your system to feel alert, sleepy, hungry, all of it, at the right times.
‘At a minimum,’ writes science journalist Lynne Peeples in her new book The Inner Clock: Living in Sync with Our Circadian Rhythms, ‘it wants you to be active during the day and restful in the evening.’ This system is constantly seeking, she says, cues from the sun.
The rays of light that crack open the sky at dawn? An invitation to flood your body with hormones to power you through the early hours of your day. Dusky skies and dimming light? Time to release melatonin, another hormone, one that brings on feelings of calm and is a precursor to sleep.
Modern life is, however, as you surely know, at fundamental odds with a thriving internal timekeeper. The beam of your phone screen as you scroll at 9pm mimics early morning light and inhibits melatonin release. Waking up in the dark during winter means hauling yourself to work while your body believes it should still be deep in REM sleep. The clocks going back – as they're set to do on Sunday 27th October – is another disrupter, to the extent that scientists from The British Sleep Society have ‘strongly recommend’ that the government breaks with tradition to keep us on Greenwich Meantime, all year.
The impacts of all of this are profound. So, how might you tilt your life in a direction that better supports your circadian rhythm? To find out, Women's Health had a conversation with Peeples on the subject that has gripped her mind for years.
This interview has been edited and condensed for clarity.
Women's Health: The phrase ‘circadian rhythm’ is one that is pretty familiar to people, thanks to conversations around the impact of blue light from screens on our ability to sleep. But what are the broader health implications of this system being disrupted?
Lynne Peeples: Acute circadian disruption is basically jet lag. When your internal clock is in a different time zone to the one you’re in, your gut’s going to feel off, you might have a headache and just not feel fully with it, and of course you might struggle to sleep at the right time.
When it's chronic – that is, your circadian rhythms are off, for a long time – that's the big worry. It's in this scenario that the science is linking greater risks of metabolic diseases like diabetes; greater risks of obesity. There's some studies linking increased rates of cancer to disrupted circadian rhythms. There's now really tantalising evidence of this correlation between dementia and Alzheimer's disease and circadian disruption.
Physically and mentally, our body systems are designed to coordinate on this internal clock. When that gets messed up our systems go awry – and and that leads to medical troubles down the line. It’s unfortunately this subtle, invisible thing happening behind the scenes that, at least until this point, has been really hard to to look at and study.
Scientists are getting to the point now of having the tools to hopefully more efficiently measure circadian rhythms, tell if they're suffering significant disruption and help people to sync them back up.
WH: How writing the book has changed your life – what steps have you taken to become more in tune with your own circadian rhythms?
LP: As I got more into the research, I started implementing some of the tips from the science into my own life. The first thing was cutting the lights at night, when it gets dark, at home. I got a huge array of electric candles around my apartment that I can turn on with a remote control. It's super cozy, and it just sets the tone, making me feel sleepier as I get less direct stimulation from blue light, plus my circadian rhythms aren’t getting that false message from the blue light that it's still daytime.
I also don’t eat anything a couple of hours before bed – I usually stop at 7.30pm – because we evolved to eat during the day. Late dinners can also throw off our internal clocks.
I also avoid alcohol – especially later in the evening – and keep a consistent sleep schedule, going to bed and getting up at roughly the same time everyday. Based on data from my Fitbit, all of this is making a huge difference to my sleep.
WH: In the book, you speak about ‘darkness deserts’ – places, often in lower income areas, which are perpetually lit, be that by harsh street lamps or flood lighting that stays on all night long. Can you say something about that?
LP: I think it is a real, real injustice that's been overlooked.
People who are financially disadvantaged are more likely to work in dark spaces – in basements; in factories. They’re more likely to be doing shift work. At night, they're more likely to live in these spaces that are overly lit. In less advantaged neighbourhoods there’s more likely to be streetlights, headlights, police lights. Both these things mess up your circadian rhythms.
There's police floodlights that I've seen put up in New York Cities social housing areas [the US' equivalent of council housing] that beam all night long. In the US, a movement known as LightJustice made up of mostly lighting designers, is trying to spread the word about these issues. Utimately, government regulation is needed to set standards, when it comes to lighting and darkness.
WH: In the book you go into how professional athletes are harnessing the power of their circadian rhythms for performance...
LP: It's a fascinating new sector in athletics science. Circadian scientists have recognised that we all peak in performance at different times of day, and that, on average, most of us peak in strength and speed in the late afternoon and early evening. The implications of this are pretty interesting.
Imagine that a football match is starting at 1pm. One team is playing at home, on their normal time zone. Another team are flying in from a time zone that’s three hours ahead. So, for the latter, it’s 4pm, in their bodies – their peak time performance. The other guys' internal clocks are maybe still going through the midday slump.
‘Chrono coaches’ are a new concept, in which scientists are advising teams and individual athletes to consider this. And there's things that teams can do to manipulate their own rhythms to set them at an appropriate time: things like using light – strategic use of daylight, light boxes and even crazier things like blue light glasses which beam blue light into your eyes.
Writing the book, I talked to Olympic athletes who arrive at the Olympic Games, after travelling across several time zones and need to get onto local time, quickly, so that their body isn't completely out of whack for their event.
WH: How does someone identify their personal kind of peak in the day, circadian rhythm wise? And how much variation is there between people?
LP: There's quite a bit of variation, booth biological – how your body naturally behaves – and artificial, variations that are based on things like our access to the cues of night and day; if we’re getting enough sunlight.
When it comes to decoding your peak, try taking some holiday time and see what happens when you let your body take the lead. Go to bed when you feel like you're ready to go to sleep. Get up when your body wakes up without an alarm clock. Do that for a few days, and then during the day, pay close attention to when you feel most energised, when you feel most alert.
And, if it’s possible, see if you can schedule your life around those times. If you can, your body will be happier – but of course, society and work patterns can make that difficult.
WH: What are your key rules, when it comes to supporting one's circadian rhythm?
LP: I point to three core clock rules that people can try to abide by. It's tricky to implement these all the time, but if you can do one or two out of three on a given day, great!
The first is to try to keep your days bright and your nights dark. That could look like getting outside for 15 minutes in the morning, even when it’s overcast or grey, and being in the daylight. Throughout the day try to spend time by a window; if you work in a dark space, try to get a few more minutes outside, where you can.
At night, cut the lights and limit your screen time.
Then, try to eat during the period of time in which we biologically evolved to eat, which is daytime. Scientists have recommend to me to stop eating at least three hours before bed.
And then, consistency: try to wake up, eat, exercise and go to bed at the same times, every day. All of these help to keep your internal clock synced up and working well.
WH: Finally, are there any misconceptions around circadian rhythms you'd like to clear up?
LP: The big one is that circadian rhythms relate to much more than sleep – they touch on so many aspects of our health and well being.
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