It’s been known for years that bright light at night affects sleep. But did you realise how dangerous it can be?
According to Harvard Medical School:
Study after study has linked working the night shift and exposure to light at night to several types of cancer (breast, prostate), diabetes, heart disease, and obesity.
Even dim light can interfere with a person’s circadian rhythm and melatonin secretion. A mere eight lux—a level of brightness exceeded by most table lamps and about twice that of a night light—has an effect,
So what is it about light at night that causes a problem?
The sun has been our natural source of light since time began. Sunlight consists of every visible wavelength of light, and beyond. From Infrared which gives us warmth, through to Ultra Violet which causes us to tan (or burn).
The wavelengths we receive from the sun vary depending upon the time of the day. At the start and end of the days, when the sun is furthest from the earth, we receive more of the red spectrum. In the middle of the day, blue is the dominant wavelength. You can see this in the redder sunrise/sunsets we get.
Lets talk about the differences:
Blue is a shorter wavelength, meaning it is higher energy. It can penetrate skin deeper, and due to it’s higher energy can cause sunburn. It’s also stimulatory. When blue light hits the retina, it signals to our brain to suppress melatonin production, to keep us awake. Melatonin is our main sleep hormone, which helps the body transition into sleep and remain there. It’s our ‘sleepy’ hormone.
Exposure to Blue light has been shown to supress melatonin for around 3 hours. So getting a blast in the evening from your smart phone, TV or LED lights (which are very blue compared to incadesent lamps) can throw your natural sleep patterns. Evening exposure to blue light tends to push our ‘sleep zone’ backwards, so we fall asleep later and wake up later.
Red light is the opposite end of the spectrum to blue. It’s thought that exposure to red light helps prepare the body for UV exposure, reducing the risk from sunburn and repairing DNA damage that might occur. This is why natural exposure to the sun over a longer period is much safer than an 11-3 stint in the midday.
Red light is also healing, and can be used to repair blue light damage to the eye, as well as increase collagen production in the skin.
Red light doesn’t suppress melatonin so is safe in the evenings.
So how can I ‘hack’ my sleep using light?
With the knowledge above, we can produce a simple plan to help regulate our circadian rhythm.
Minimise blue light exposure 2 hours before bedtime
To minimise blue light exposure, the best method is not to use laptops, mobile phones or TVs, or use any LED or fluorescent lights. This may feel like you’re back in neanderthal times, so there are a few mitigation tips:
- Download Flux for your laptop or phone (Android only). This is a program which automatically shifts the spectrum of light emitted from your device into the red end of the spectrum. I find the default settings aren’t quite enough, so if you go into the settings and drag the slider to around 3000K or below. There should be a slight orange tint to your screen, which you’ll soon stop noticing.
- Turn on Night Shift for your iPhone or Macbook. Again, you might want to shift the settings a little to make it redder than default
- Use redder spectrum lamps. Himalayan Salt lamps are ideal as they don’t emit any blue. Alternatively red-coated incandescent bulbs. Candles or open fires are also ideal.
- Avoid using your phone if you wake up – this will suppress your melatonin making it very difficult to get back to sleep
- Use blue-light blocking glasses, this way you can operate a bit more freely without worrying. You can buy ‘Uvex’ safety glasses very cheap, or more fashionable Swanwick shades.
- Black out of your room. Even a few lux can lead to sleep disturbances and health issues. Ensure your curtains are tightly closed, use black-out blinds if you need.
- Turn off any gadgets which have standby lights, or cover the lights with tape.
Get dose of light in the morning
When you wake in the morning, once it reaches your ideal waking time (not before) get a dose of morning sunshine. Ideally get outside within 30 mins and spend 15 mins or so exposed to the natural light without any glasses or contacts. This ‘sets’ your wake up time and lets the body know it’s time to wake up. This increases morning cortisol which gives you energy to set about your daily tasks.
If you wake up early, simply keep your blue light limited until your idea wake up time.
A good dose of daytime blue light actually increases our ability to sleep at night, so grab some rays at lunchtime!