Sign up FAST! Login

Why We Can't Fall Asleep

Why Can't We Fall Asleep? - The New Yorker

Stashed in: Sleep!, Light, New Yorker, Remind Me, MIT TR

To save this post, select a stash from drop-down menu or type in a new one:

But it may be that the most important aspect of sleep hygiene has to do with light—which, of course, has gotten more pervasive during the past century, especially at night. Humans have evolved to be exquisitely sensitive to the most minute changes in the light around us. In fact, there are specific photoreceptors in the eye that only respond to changes in light and dark, and which are used almost exclusively to regulate our circadian rhythms. These melanopsin receptors connect directly to the part of the brain that regulates our internal body clocks. They work even in many people who are blind: though they can’t see anything else, their bodies still know how to adjust their circadian clocks to stay on schedule. Light helps the body predict the future: it’s a sign of how our environment will change in the coming hours and days, and our bodies prepare themselves accordingly. As the Harvard circadian neuroscientist Steven Lockley told me, “Our clocks have evolved to anticipate tomorrow.”

Now, however, that natural prediction system is being constantly wrong-footed. The problem isn’t just artificial light in general. Increasingly, we are surrounded by light on the short-wave, or “blue light,” spectrum—light which our circadian systems interpret as daylight. Blue light emanates from our computers, our televisions, our phones, and our e-readers; ninety per cent of Americans use electronic devices that emit it. When we spend time with a blue-light-emitting device, we are, in essence, postponing the signal to our brain that tells it that it’s time to go to sleep. (“What have we done with our dusk?” Charles Czeisler asks.) When “dusk” gets pushed progressively later because of these false light cues, we get a surge of energy rather than the intended melatonin release.

Czeisler has found that artificial light can shift our internal clocks by four or even six time zones, depending on when we’re exposed to it. In one study, out earlier this year in the journal PNAS, Czeisler and his colleagues asked people to read either a printed book or a light-emitting e-book about four hours before bed, for five evenings in a row. The effects were profound. Those who’d read an e-book released less melatonin and were less sleepy than those who’d read a regular book; their melatonin release was delayed by more than an hour and a half, and their circadian clocks were time-shifted. It took them longer to fall asleep. The next morning, they were less alert. These resetting effects can result not just from prolonged reading but from a single exposure. In his sleep lab, Lockley has seen it happen after exposing subjects to short-wavelength light for less than twelve minutes.

So... we can't fall asleep because of light?

Light is one of many reasons.

all negatively impact sleep, the more so the closer they’re consumed to bedtime. We fall asleep faster when we exercise and have regular mealtimes. Eat too late or too much and sleep becomes more elusive. (The effect is reciprocal: sleep disturbance is associated with weight gain.) Go to bed hungry, and sleep likewise escapes your grasp. Any schedule variability, in fact, may detract from sleep ability: in some preliminary results, Rosalind Picard, the director of the Affective Computing Research Group at M.I.T.’s Media Lab and the co-director of the Advancing Wellbeing Initiative, found that sleep variability was one of the most important factors in determining how well someone slept: it was better to go to bed at a consistent time than to try to pull an all-nighter tonight and “catch up” tomorrow. Regular sleep schedules also predict better G.P.A. and mood.

Okay, so:

LESS light.

MORE exercise.

LESS eating late. 

MORE keeping to schedule. 

That's a GREAT reminder list!

Yes, if only I knew how to turn it into a picture!

You May Also Like: