Hyperarousal is a term I mention when people want a quick explanation for what’s behind insomnia. The word seems to resonate. Think of hyper- as in “excessive” or “extreme”; arousal, meaning “activation” or “animation.” Or plain old hyper, meaning “very excited, nervous, or active.”
Many people with insomnia tell me they have an overactive mind at night. They’re chewing over a problem and just can’t stop. Or they’re thinking ahead and worrying they won’t have time to get everything done.
Some insomniacs talk about feeling wired: “Something will wake me up,” Amy explained in an interview, “and my heart’s racing and it can feel almost like an adrenaline feeling. I’m nervous and I can’t shut down—that’s the experience I have.”
“Hyperarousal” is a pretty good way to describe the feeling of insomnia at night. But is there a test for it? Does it happen only at night, or do insomniacs experience hyperarousal 24/7?
Measures of Hyperarousal in Body and Brain
When researchers test for physiological arousal, the differences that show up between people with insomnia and normal sleepers are fairly small. On measures of heart rate, metabolism, stress hormones, and possibly body temperature, the tests show, on average, that insomniacs are cranked up a notch—but just a notch—higher on the arousal scale than normal sleepers.
Studies of brain waves at night—when they involve something called power spectral analysis—are slightly more revealing. Normal sleepers’ brains cycle tidily through all the sleep stages.
The brains of people with insomnia cycle through all the sleep stages as well. But mixed in with the usual theta and delta waves are high-frequency wave forms normally associated with being awake and alert and solving problems. This beta activity that shows up in insomniacs’ brains at night suggests that low-level information processing may be occurring even as we sleep. It’s commonly cited as evidence of insomniacs’ hyperarousal at night.
These differences between insomniacs and normal sleepers may help explain the trouble we have tuning out, mentally and physiologically, at night. But neither the physiological differences nor the beta activity at night are considered to be definitive proof of insomnia.
Hyperarousal in the Daytime
You might not think that hyperarousal describes how insomnia feels during the daytime. When morning comes, your complaint is probably that you’re not aroused enough. You feel fatigued and low energy, brain-fogged and unable to think clearly. It’s a major struggle to function, let alone get through the day.
But these complaints may actually be manifestations of hyperarousal during the daytime. European researchers used high-density electroencephalography (a fine measure of electrical activity in the brain) to investigate the brain waves of insomniacs and normal sleepers when they were awake. They placed electrodes on participants’ scalp and took readings when they were in a resting state, with (1) eyes open and (2) eyes closed.
- With their eyes open, the participants with insomnia had comparatively lower alpha power. (Alpha waves are prominent when we’re in a relaxed state of consciousness and not making an effort to do anything.) Lower alpha power would be consistent with less ability to calm down and less ability, in the face information overload, to filter out what’s unimportant or irrelevant.
- With their eyes closed, the insomniacs experienced significantly more beta power than did the normal sleepers. In the authors’ words, “The widespread high power in a broad beta band reported previously during sleep in insomnia is present as well during eyes closed wakefulness, suggestive of a round-the-clock hyperarousal.”
If insomnia really does derive from round-the-clock hyperarousal, then treatments focused only on extending sleep may not do much to mitigate our daytime symptoms. Better solutions will improve the quality of both our nights and our days.
If you have insomnia, do you experience a feeling of hyperarousal during the daytime? How exactly does it feel?