Many people are terrible judges of how much shut-eye they get, which reveals a striking fact about insomnia:
You can have insomnia and still get an adequate number of hours of sleep. New research is showing that insomnia is less about the amount you sleep and more about what your brain does during sleep.
About 30% of American adults have symptoms of insomnia each year, according to scientific studies. And about 10% of the population has chronic insomnia, which is generally defined as having difficulty sleeping at least three times a week for three months or more.
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About half of those with insomnia sleep a normal amount, or at least six hours a night. In one study, about 42% of people with insomnia who slept a normal amount underestimated how much they slept on a particular night by more than an hour. Only about 18% of normal sleepers underestimated by that much. The study, published in 2011 in Psychosomatic Medicine, followed 142 people with insomnia and 724 controls.
By contrast, people who don’t sleep much overestimate how much they sleep.
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While everyone wakes up during the night, “if you’re a good sleeper, it means you don’t remember wakefulness.”
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Some studies suggest that worry is linked to a misperception of sleep.
Also, some research has revealed that people with insomnia have more high-frequency brain waves—ones that are usually associated with wakefulness—while they are sleeping.
“People seem like they are not wholly unconscious,” says Michael Perlis, director of the Behavioral Sleep Medicine Program at the Perelman School of Medicine at the University of Pennsylvania. “There is more sensory processing, more information processing, more short- and long-term memory than you should have in an unconscious state.
Indeed, there’s new evidence that the brains of people with insomnia act differently during sleep than those of normal sleepers. Daniel J. Buysse, a professor of psychiatry and clinical and translational science at the University of Pittsburgh School of Medicine, has been using PET scans, which measure metabolic activity in the brain, to scan the brains of people with insomnia and normal sleepers.
He and colleagues have found that in people with insomnia, parts of the brain known as the default mode network are more active during sleep, compared with normal sleepers. The default mode network is most engaged when peoples’ minds wander and when they’re being self-reflective.
“Insomnia is not the problem of too little sleep. It is the problem of too much brain activation,” Dr. Buysse says. “When patients tell us, ‘My mind is wandering, I’m thinking all night, I’m aware of everything that’s going on,’ it is entirely possible that their experience of sleep is exactly how they describe it.”