Why Can’t We Fall Asleep?

BY MARIA KONNIKOVA

This is the first piece in a three-part series on sleep. The second concerns sleeping and dreaming.

Here’s what’s supposed to happen when you fall asleep. Your body temperature falls, even as your feet and hands warm up—the temperature changes likely help the circadian clocks throughout your body to synchronize. Melatonin courses through your system—that tells your brain it’s time to quiet down. Your blood pressure falls and your heart rate slows. Your breathing evens out. You drift off to sleep.

That, at least, is the ideal. But going to sleep isn’t always a simple process, and it seems to have grown more problematic in recent years, as I learned through a series of conversations this May, when some of the world’s leading sleep experts met with me to share their ongoing research into the nature of sleeping. (The meetings were facilitated by a Harvard Medical School Media Fellowship.) According to Charles Czeisler, the chief of the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital, over the past five decades our average sleep duration on work nights has decreased by an hour and a half, down from eight and a half to just under seven. Thirty-one per cent of us sleep fewer than six hours a night, and sixty-nine per cent report insufficient sleep. When Lisa Matricciani, a sleep researcher at the University of South Australia, looked at available sleep data for children from 1905 to 2008, she found that they’d lost nearly a minute of sleep a year. It’s not just a trend for the adult world. We are, as a population, sleeping less now than we ever have.

The problem, on the whole, isn’t that we’re waking up earlier. Much of the change has to do with when we choose to go to bed—and with how we decide to do so. Elizabeth Klerman is the head of the Analytic and Modeling Unit, also in the Sleep and Circadian Disorders division at Brigham and Women’s Hospital. Her research tracks how multiple individual differences in our environment affect our circadian rhythms and our ability to fall asleep easily and soundly. “When you go to bed affects how long you can sleep, no matter how tired you are,” she told me.

A wide array of factors can determine just how quickly you’ll be able to drift off to sleep when you choose to do so. To determine their relative importance—and separate the things that truly make a difference from the ones that aren’t all that essential—Klerman first assesses her subjects’ habits and histories: What is their sleep-wake history—that is, what are their usual routines, and what are the problems they’ve encountered in the past? What about pharmaceuticals: Which do they use, and are any targeted as sleeping aids? Once this information has been gathered, she brings them to the lab, monitors their sleep in a controlled environment, and determines how each of the various factors affects the ability to fall asleep.

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