The human (and other species, really) body has a 24-hour clock, which is scientifically called the circadian rhythm. This process allows our bodies to do all of their biochemical, physiological and mental tasks. Light is one of the key contributors to this cycle. Daylight is especially important for the cycle that leads to sleep; this is why exposure to natural light is a key part of having a good night's sleep. It's the reason our bodies wake in daylight and want to sleep at night. But how does artificial light affect sleep?
Our eyes naturally respond to light this makes it hard to sleep after being exposed to it. Think of stimuli that comes from a late night work session in front of a backlit screen, the light in the hallway or even the digital alarm clock on the night stand -- all these can interrupt sleep. Exposure to artificial light delays or even suppresses the release of melatonin, a hormone that encourages sleep. Artificial light essentially leads to your brain constantly thinking that it's daytime.
Gadgets like the ipad, cell phones and ereaders affect sleep more than, say a lamp, because the gadgets are often closer to the eyes and the light hits the eyes directly.
How then does one keep their circadian rhythm uninterrupted and ticking on as close to normal as possible as well as produce adequate levels of melatonin?
The most important part of keeping your 24-hour cycle going is getting as much daylight as possible.
As mentioned earlier in the post, it's important to avoid using backlit screens at least three - four hours before your bedtime. Switching off the lights in the bedroom at least 15 minutes prior to bedtime will also go a long way in giving your pineal gland the amount of darkness it needs to start producing melatonin. Being a dimly lit to dark room is how your body and brain will know that it's time to sleep.
If you can, avoid turning on the lights during the night if you have to wake up for some reason.
Use an eye mask in order to intensify the darkness in your bedroom if you must.
My child is afraid of the dark... Doesn't a night light affect their sleep?
The answer to this is: having the lights on will certainly affect the child's sleep. But a child who is afraid of the dark won't sleep any better if they don't feel safe. With this mind, it might be worth breaking the night light rule to get the child comfortable. Scientists recommend that it be 25 watts and glow red. Red light has been proven to not interfere with melatonin production as much as blue and white lights do. Night lights, provided they stick to these above specifications, are not the enemy.