Understanding your body’s relationship with light can help you sleep better and wake up refreshed, finds Charlotte Martyn. A few simple changes to your bedroom and routine will make all the difference…
Whether or not you have something you’d consider a bedtime routine, it’s almost certain that the last thing you do before you fall asleep is turn out the light. We all understand that it’s easier to sleep when it’s dark, but the relationship between light and sleep is much more important than you might imagine.
The invention of artificial light means society and the human body are no longer reliant on the natural prompts of dawn and dusk to wake up and fall asleep. And yet despite the lure of late-night videogame sessions, the necessity of working late at your laptop or the urge to get to the gym before the sun’s up, your body’s internal clock will still be working to a more fundamental timetable that’s closely tied to natural light.
Dr Vikki Revell is a chronobiologist at the University of Surrey and studies the non-visual effects of light on physiology, behaviour and sleep patterns. She says that key to understanding how light affects our sleep is the concept of that internal body clock – more specifically, circadian rhythms. “There are rhythms in your physiology and behaviour that take about 24 hours to complete,” she explains. “The most obvious one that you’ll be aware of is your sleep-wake cycle – when you go to bed each night and get up each morning. But it goes beyond that. There are all sorts of things, like how your body handles food, or your behaviour and ability to perform cognitively, that change across the day. The reason is that your body can’t work at an optimal level for 24 hours continuously, it needs a rest.”
Most people’s body clocks run slightly longer than 24 hours, though for some people it’s slightly less, and Vikki says that light is vital for keeping you on track. “To stay synchronised to a 24-hour day you need a daily cue from the outside world, and it’s the light/dark cycle that’s important for synchronising your clock and holding it on exactly 24 hours,” she explains. “For most people, because their body clock runs at slightly longer than 24 hours, you need a light signal in the morning that says ‘it’s morning, we’re re-starting’. For people whose clock runs at less than 24 hours, they need a bright light in the evening to keep them functioning a bit longer to keep it on a 24-hour rhythm.”
