Staring at a backlit screen at 11pm may make your eyes feel tired but it's having the opposite effect on your whole body clock

King Henry IV was blaming his lack of sleep on worry over his wayward son and heir. But several centuries later, millions of people are having much the same problem wilting their own eyelids down. Only now the main culprits are our beloved technologies and their steady, silent invasion of our bedrooms.

The tiny light of your computer or phone winking at you in the dark might seem harmless enough, but it's having an insidious effect on the amount and quality of your sleep.

Blue light emitted from mobile phones, digital alarm clocks, modems, computers, TV sets and even smoke detectors often play havoc with our natural circadian rhythms. This means reduced quality of sleep, especially Rapid Eye Movement (REM) sleep which is the deepest cycle and the most necessary for proper physical and mental rejuvenation.

In 2011, a large scale poll by the National Sleep Foundation in the US tracked the average punter's use of communications technology in the 60 minutes before bedtime. (It's a fair bet that the stats wouldn't be all that different for Aussies.)

The report states that the use of communications technology in the hour before going to bed is "pervasive" with a whopping 95% of respondents reporting habitual use of electronics several times a week in that crucial 60 minutes before hitting the pillows.

Light-emitting screens are the baddies here. Evening exposure to this kind of artificial light pushes our circadian rhythms forward by about an hour and also suppresses our body's release of melatonin, which is a natural sleep-inducing hormone, necessary for quality sleep. Staring at a backlit screen at 11pm may make your eyes feel tired but it's having the opposite effect on your whole body clock.

The National Sleep Foundation's survey found that surfing the internet on a computer or laptop was the most popular pre-bedtime activity with an overall score of 61%. This was closely followed by watching television, which scored 56%. Using a mobile phone came in with 29% and playing video games ranked at 21%.

Overall, almost two thirds (63%) of respondents admitted their sleep needs weren't being met during the week. This is an alarming statistic, given that chronic lack of sleep can lead to all kinds of nasties. And we're not just talking the big guns like diabetes, heart disease and stroke, but also many other conditions that are less dramatic but still debilitating. Like reduced memory, attention span and poor concentration. Not a good combo with your TAFE studies.

There's also the small matter of increased risk of accidents. I don't mean to be alarmist, but sleep deprivation was a key factor in the 1979 nuclear accident at Three Mile Island, the disastrous Exxon Valdez Oil spill and the 1986 nuclear meltdown at Chernobyl. Just a few more good reasons to turn your electronics off at night.

Kinda makes King Henry's woes about his capricious son and the future of his kingdom seem like a walk in the park.