Insomnia is characterized by greater alpha wave activity at nightPicture the brain at night. It’s mostly quiet except during rapid eye movement (REM) sleep. Then clusters of neurons in the brain stem start firing away like mad. These bursts of activity are perfectly normal during REM sleep, alternating with periods of quiet non-REM sleep through most of the night.

The brains of people with insomnia are more active at night—even during non-REM sleep. This activity isn’t often noted in sleep studies, where the point is to identify dominant wave forms. But looking closer, scientists are discovering slight but crucial differences in insomniacs’ brain waves at night, which may explain our trouble falling and staying asleep.

Alpha wave intrusion is a term used to describe the wake-like brain activity observed during the deep sleep of people with fibromyalgia and major depression. Now a new study in the Journal of Sleep Research presents evidence of abnormal alpha wave activity in insomniacs’ brains at night. Here are the two main findings:

Trouble Falling Asleep

The descent from wakefulness into deep sleep occurs fairly quickly in healthy sleepers. The pressure to pay off the day’s sleep debt is strong, compelling a rapid descent into deep (slow-wave) sleep.

But in people with sleep onset insomnia, who typically take more than 30 minutes to fall asleep at night, the descent takes quite a bit longer, research shows. Insomniacs—for unknown reasons—seem to have reduced sleep pressure. Not only does it take us longer to fall asleep. It also takes us longer to descend into deep sleep, the really restorative stuff.

Why the Slow Descent?

The research team investigating alpha wave activity looked at the sleep studies of 18 good sleepers and 10 insomniacs and found one difference that occurred before sleep began. Alpha waves—associated with a relaxed, meditative state of consciousness that occurs when the eyes are closed—are predominant in the period leading up to sleep. They’re generated by neurons firing at frequencies of 7.5 to 12.5 cycles per second.

As the healthy sleepers in the study were falling asleep, the alpha rhythms in their brains began to fluctuate and decay. But the alpha wave activity in insomniacs’ brains continued going strong.

Sleep onset insomnia may have something to do with decreased alpha variability, the researchers concluded. Insomniacs are relaxed and ready for sleep—yet (again for unknown reasons) we remain stuck in alpha mode.

Waking Up at Night

Alpha waves may also play a role in sleep maintenance insomnia. Polysomnogram studies show that normal sleepers awaken at least a few times a night but are mostly unaware of these awakenings.

People with sleep maintenance insomnia, in contrast, are conscious of waking up at night. These awakenings make our sleep feel fitful and less restorative. (And some sleep maintenance insomniacs are told their problem involves alpha wave intrusion following a sleep study.)

Adults spend up to 80% of the night in non-REM sleep, and in the alpha wave study, different kinds of alpha activity occurred in the brains of healthy sleepers and insomniacs throughout non-REM sleep. Brief arousals in the healthy sleepers were characterized by alpha waves that stayed well below the frequency of alpha waves during conscious wakefulness.

But the alpha frequencies in participants with insomnia rebounded to wake levels. In this situation, a sleeper might be easily awakened by noise or movement and memories could be formed. It might account for why so many insomniacs complain of light and/or broken sleep.

The Take-Away

Higher alpha frequencies during brief arousals and lower alpha variability at the approach of sleep fit with the hyperarousal theory of insomnia, which suggests that people prone to insomnia experience higher levels of arousal around the clock. As for how to correct these alpha abnormalities, we’ll have to wait and see.

Posted by Lois Maharg, The Savvy Insomniac

Lois Maharg has worked with language for many years. She taught ESL, coauthored two textbooks, and then became a reporter, writing about health, education, government, Latino affairs, and food. Her lifelong struggle with insomnia and interest in investigative reporting motivated her to write a book, The Savvy Insomniac: A Personal Journey through Science to Better Sleep. She now freelances as an editor and copy writer at On the Mark Editing.


  1. This alpha wave hyperarousal sounds exactly like me.



    1. Hi Brett,

      Some people with insomnia experience even higher-frequency brain activity at night in in a few key areas of the brain while the rest of the brain is asleep. This may explain the sensation of being aware of what’s going on in the environment—and perhaps even processing thoughts—while a sleep study would indicate that you were asleep.

      You might be interested in this blog post about paradoxical insomnia:



  2. I have completed 12 weeks of CBT-I and now have a sleep window of 11.15pm – 6am. I used to wake 5-7 times a night before sleep restriction but even now, I often wake 3-5 times a night which means I am tired during the day and much more clumsy than when I was having more hours in bed, even if not asleep. I fall asleep again more quickly than I used to but I do worry that I’m not getting enough refreshing deep sleep. Can you suggest anything which might help me stay asleep for longer periods, please. I don’t want to give up on the sleep restriction but I am starting to feel that I will never get a full nights sleep.
    your website is so reassuring, many thanks for all your research



    1. Hi Beverley,

      Feeling tired and clumsy during the daytime is certainly not where you want to end up after 12 weeks of CBT-I. The sleep restriction process—by shortening, and then gradually lengthening, sleep—typically helps people consolidate their sleep. Sleep then feels deeper and more refreshing compared with sleep that’s interrupted by wake-ups.

      Somehow it hasn’t worked that way for you although you’ve devoted 12 weeks to it (certainly plenty of time).

      I’m wondering if you consulted a sleep specialist before starting on CBT. Regardless of whether you did or didn’t, I think you should see one now.

      The daytime symptoms are concerning and suggest that something other than simple insomnia may be going on. One thing that comes to mind is the possibility of the wake-ups and the daytime tiredness being a sign of sleep apnea. There are other possibilities as well.

      These things really need to be checked out if they haven’t been ruled out already. Having an overnight sleep study is the way to do it—which is my reason for recommending a consultation with a sleep specialist.

      Best of luck in connecting with someone trained to sort out the reason for your nighttime wake-ups.



      1. Thanks Lois
        I have seen a consultant who said he didn’t feel I had any underlying sleep phase problems and that I would probably be on sleep restriction for life. He also praised the meticulous way I have stuck to the CBT-I so I know I’m doing it properly with the help of a professional CBT therapist. I’ve been checked for sleep apnoea and also seen an ENT consultant to rule out any breathing problems so I’m not sure what to try next!

        I’ve done sleep school and mindfulness for sleep and after 15years of walking during the night every night, I don’t lie awake worrying about it but I would love to go to sleep one night and wake up and find it is morning!


      2. Hi Beverley,

        It sounds like you’ve seen all the right specialists for the wake-up problem and had several possible diagnoses ruled out. I’ll keep my eyes posted for new research on middle-of-the-night awakenings and strategies other than those you’ve tried for curtailing them.

        Researchers explain some middle-of-the-night awakenings as occurring in people who have a higher rate of “cyclic alternating patterns”—repetitive brainwave patterns that occur during non-REM, or quiet, sleep, which cause sleep to become less stable. But to my knowledge no one has proposed what, if anything, can be done to alter the CAP rate. Again, I’ll keep looking for new information.


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