London - I'm tired. I barely know anyone who isn't. Complaining about exhaustion seems to have become the norm; if I hear someone trilling about how refreshed they're feeling, I look at them with the suspicious expression I normally reserve for friends who unexpectedly confess to having let Jesus into their life over the weekend.
As a nation, we're utterly knackered, and we enjoy listing all the potential reasons that we're feeling so rough, from colossal workload to prolonged building work next door. But here's a theory: maybe the LED screens we bury our faces in are playing havoc with our ability to synchronise with the 24-hour day. That's the view of Charles Czeisler, professor of sleep medicine at Harvard Medical School.
Czeisler has long believed that artificial light is profoundly affecting the way we live; compared to 40 years ago, 10 times more of us are getting fewer than six hours shut-eye, and on average we're sleeping about two fewer hours than we ought. Sling caffeine into the mix - which we love to do, and which food and beverage manufacturers are increasingly keen on doing - and it's a wonder we're not all stumbling about at 3am, wondering where the hell we left our circadian rhythms.
Normally, the name of Margaret Thatcher is invoked at this point - she managed on four hours a night and still stuck it to the unions, etc - but the fact is that lack of sleep can lead to weight gain, diabetes, cardiovascular problems, burnout and depression.
Czeisler reckons that the colour temperature of energy-saving bulbs and LEDs is preposterously unsuitable for use after dusk. Their blueish tinge has more in common with midday light than the softer, yellower light that you get later in the day, and so our brains and bodies become confused.
Add to that the gadget addiction that has us prodding screens at midnight - so called, I hear, because it's the middle of the night - and our body clock suddenly gets shifted four hours westward, putting me somewhere off the coast of Newfoundland. I don't want to be there. I want to be in bed.
The solution, according to Czeisler?
Take the TV out of the bedroom.
Maybe use halogen bulbs.
Download a handy app for Windows and Mac called f.lux, which slowly fades your screen to a more dusky colour temperature as the sun sets.
Avoid drinking bedtime cocoa in a room that has lighting reminiscent of your local sub-post office.
And if all else fails, do what a former boss of mine did when the brightness control broke on the expensive LED screen in his office: wear sunglasses indoors. You might look stupid, but you'll get a cracking night's sleep.- The Independent