Our resident sleep expert Christabel Majendie (MBPsS) returns to explain the links between sunlight and sleep and how to improve your sleep health using the power of light.
Particularly during the winter months, there’s always a temptation to stay indoors and not venture outside into the cold - but did you know this could adversely affect your energy levels in the day and your ability to sleep at night? It’s important for your sleep, mood and physical health to spend time outside and expose yourself to natural light, whatever the weather or the season.
Watching the clock
The connection between sunlight and sleep comes down to biology. Our bodies have evolved to work in partnership with the natural, twenty-four-hour-cycle of light and darkness. All living organisms, including humans, have developed a biological, internal clock that is tied to this day/night cycle.
This clock is called the circadian rhythm and it influences the timing of many biological processes, including the sleep/wake cycle. Science has now shown that every cell in the human body has a molecular clock and these are synchronised by an area in the brain called the SCN or ‘master clock’.
How do our bodies respond to sunlight?
The timing of circadian rhythms varies from person to person and, to a large degree, this is due to genetics. But it’s also influenced by light. This means the circadian rhythm can be anchored to the day/night cycle in the local environment. It also means the body clock can be disrupted by artificial light and spending too little time outside in natural light.
Even on a cloudy winter's day, the light outside is twenty-five times brighter than indoor lighting. On a summer’s day it can be five hundred times brighter. And the light outside varies across the day, unlike constant, artificial light. Why does this matter?
How important is sunlight to our circadian rhythm?
Our eyes contain cells that detect the brightness of light and they send this information to the ‘master clock’ in the brain. The contrast of light across the twenty-four-hour period is then used to determine the timing of the circadian rhythm going forward.
If we are spending a long time inside with artificial light (which is both constant and relatively weak compared to natural light), the circadian rhythm will be weakened. This means the sleep/wake cycle will be less pronounced, that is, you may feel less alert during the day and less sleepy at night.
How does the timing of light exposure affect our sleep?
In addition, the timing of light can influence the timing of the circadian rhythm. Bright, artificial light in the evening can confuse the body clock, by suppressing the release of melatonin, the hormone that helps us to feel sleepy.
Light from electronic devices that are positioned close to the eyes, such as phones, tablets and computers, can add to this disruption. This can cause problems falling asleep and staying asleep. It can also delay the body clock so this sleep disruption may continue on future nights. In addition, you may find you struggle to wake in the morning having not had enough sleep and this will lead to problems with alertness and energy in the day.
Reducing your light deficit
What’s the solution? Thankfully, it costs nothing and it’s completely natural! We need to spend more time outside in natural sunlight. Take every opportunity to be outside, whatever the weather. Exercise outside; have lunch outside; take regular breaks outside; take a daily walk or cycle; take phone calls outside; take up gardening.
When it’s light in the morning, open all the curtains and blinds at home. If you work from home, position yourself to face a south-facing window. Don’t use blinds or curtains during the day. Get as much natural sunlight into your house as possible.
In addition, reduce the lighting at home in the evening. Use dimmer switches, side lamps with low wattage light bulbs or even candles! When it’s dark outside, switch to warmer red or orange lights and put away the electronic devices until the morning. Use curtains or blinds at night to block out street lights.
The importance of sunlight for our health cannot be overstated, and this extends to our sleep health too. By taking these simple measures – spending more time outside and reducing light exposure in the evening- you’ll find you are sleepy earlier in the evening, making it easier to get to sleep.
Your sleep quality will probably improve as your circadian rhythm strengthens. If you are getting to sleep earlier because you are sleepy earlier, you are more likely to naturally wake early feeling refreshed, without the need for an alarm which can cut short your sleep.
This means you will be getting the right amount of sleep which will benefit your long-term health. In addition, getting better quality sleep and spending more time outside in natural sunlight will improve your levels of alertness during the day, meaning better focus, concentration and a brighter mood.
