In 2018, Hannah Scott, a sleep researcher at Flinders University, waited for a woman to fall asleep.
This can take time when the subject is connected to equipment measuring brain activity, eye movement, heart rate and muscle activation. But about 30 minutes after the woman closed her eyes, Scott saw the telltale signs of sleep from the electroencephalogram, or EEG: a shift to lower-frequency brainwaves.
The woman progressed into deep sleep, and “was there for quite a while”, Scott said. Then, the woman suddenly woke up, saying she had to go to the bathroom. As Scott detached her from the machines, the participant apologized, saying she felt terrible she hadn’t been able to fall asleep yet.
“She was absolutely adamant that she hadn’t slept,” Scott said, who had just watched her sleeping.
When a person is sleeping, but doesn’t know they are, this is called sleep state misperception. If woken up, a person will say they were awake the whole time.
It’s a frequent issue in insomnia, said Matthew Reid, a neuroscientist and sleep researcher at Johns Hopkins School of Medicine. An insomniac may say they have barely slept, but when tested in a sleep lab, they might actually be sleeping a normal number of hours per night. This leads to a conundrum: how does someone feel rested when they are sleeping enough – but just not realizing it?
This experience, which afflicts a significant number of insomniacs, has had various names: paradoxical insomnia, subjective insomnia, sleep state misperception and, most recently, subjective-objective sleep discrepancy.
By any name, the phenomenon reveals that we don’t always know when we’re asleep or awake, and that our beliefs about sleep influence how rested we feel. At the same time, researchers are finding that people with paradoxical insomnia may not be entirely wrong; there may be something real that lies between sleeping and wakefulness.
What is paradoxical insomnia?
Paradoxical insomnia is a subcategory of insomnia. People with it report that they only sleep a few hours a night and don’t feel rested. But sleep studies show they are getting more sleep than that – sometimes even a typical amount.
People with insomnia seem to suffer from straightforward problems: trouble falling asleep, staying asleep and getting enough sleep to feel rested. Their sleep issues make them tired during the day; they have difficulty concentrating, and feel irritable and grumpy.
But total sleep time doesn’t always differ by much between healthy sleepers and people with insomnia. On average, according to one meta-analysis, insomniacs sleep just 23 minutes less per night than healthy sleepers. If time asleep isn’t the whole story, what is?
Of course, some people need more sleep than others. But it turns out some people don’t perceive their sleep accurately. They do not seem to remember that they did sleep. They may sleep a full night, but not feel rested. These studies revealed that insomnia can be a more complex experience than it appears.
In 1959, French doctors first described a patient whose observed sleep time didn’t match up with how many hours she thought she slept. The doctors named the condition fausse insomnie or false insomnia, and believed it was caused by her being overly worried about sleep. Since then, many sleep doctors and researchers have noticed that insomniacs’ sleep complaints don’t always align with the amount of sleep they are observed to get.
Researchers don’t have a unified estimate of exactly how prevalent paradoxical insomnia is because it has multiple names. But it’s far from rare, Reid said. By some accounts, about half of people with insomnia sleep less than six hours a night, while the other half sleep more than six hours, an amount comparable to good sleepers’ sleep time.
Who experiences paradoxical insomnia?
Many people – even good sleepers – may think they’re still awake in the early stages of sleep. But people with paradoxical insomnia are more likely to think they’re awake after the first two hours. They are also more likely to report feeling awake during REM sleep, when almost all good sleepers will report accurately that they were sleeping. In serial awakening studies, people with insomnia who are woken up multiple times throughout the night will report being awake when they had actually been asleep more often than good sleepers.
Thomas Andrillon, a cognitive neuroscientist at the Paris Brain Institute, has a hunch that awareness during sleep is more nuanced than previously believed. In experiments about memory and learning during sleep, he would see someone sleep, confirmed by their brain activity in real time. Afterwards, they would insist they hadn’t slept. Andrillon realized he had experienced this himself, and that plenty of others did, too – such as his students, who would fall asleep in class, but have no idea they had drifted off.
Most people have gone through this, even if they’re not insomniacs. For instance, when I’m trying to sleep before an early morning flight, I usually feel like I haven’t even slept an hour. Yet I can recall a dream about, say, sleeping through my alarm, which tells me otherwise. I’ve sat next to a family member on an overnight flight who peacefully passes out, only to arrive at our destination and complain they didn’t sleep.
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“You think you got zero sleep the entire night, and something reminds you that’s objectively not true, like somebody tells you: ‘Oh, you were snoring,’” Reid said.
Why does paradoxical insomnia occur?
Until recently, many researchers thought that people with paradoxical insomnia were incorrectly reporting their own experience. But brain imaging done by Andrillon and his colleagues is suggesting that insomniacs with discrepancies between their sleep and wake times might not be entirely wrong. Instead, they might be noticing a unique altered state of consciousness.
Sleep researchers determine someone is sleeping when they lose awareness of the world around them, and when their brain activity shifts to high-amplitude, low-frequency oscillations. EEG readouts will feature sleep signatures like slow waves and sleep spindles, or specific bursts in activity.
But commonly used observational techniques might miss the nuances of brain activity during the transition into sleep, or the moments between sleep stages, Andrillon said. The technology might not be sensitive enough to capture “wake-like” brain activity that could explain the feeling of being awake while sleeping. Andrillon said that when other researchers have studied deeper areas of the brain, they found signs of arousal, even when people seemed asleep.
“The fact that they look like they’re sleeping is true only at a superficial level,” Andrillon said. “When you dive a bit more in the details of the brain activity, you see signs of wakefulness that you will typically not see during normal or standard sleep.” Experts are now shifting to the term subjective-objective sleep discrepancy, or SOSD, rather than paradoxical insomnia or sleep state misperception.
In a study from March, in a group of more than 800 people with insomnia, 24% had subjective-objective sleep discrepancies. Andrillon and his colleagues found differences in the physiological profile between the two kinds of insomniacs. People with SOSD didn’t wake up very often, but when they did, their waking state was tainted with signatures of sleep, which could influence their judgment about not sleeping well or not having slept, he said. Conversely, the sleep of insomniacs without SOSD had wake-like features, meaning their sleep was of a lesser quality.
Are there solutions for paradoxical insomnia?
CBT-I, or cognitive behavioral therapy for insomnia, is a well-researched and effective way to improve sleeping habits. It seems to help people with SOSD, too. In a study from last year, Scott and colleagues found CBT-I had no difference in positive outcomes for people with regular insomnia, compared with those who had SOSD. Other studies have shown that CBT-I can improve issues related to SOSD.
It won’t be useful to become overly worried about whether you’re getting the perfect amount of sleep, Scott said. There is an association between SOSD and anxious or worried thoughts about sleep, so try not to pile on additional worries. “People who have [SOSD] tend to have certain thoughts, very often involving rumination about worries of the day, worries of not sleeping, not being able to sleep,” Andrillon said.
Instead, a helpful tool for paradoxical insomnia could be a strategy called paradoxical intention, which encourages poor sleepers to stop trying so hard to sleep.
Previously, people who could not tell they were asleep were perceived to have flawed judgment. Actually, SOSD is a reminder that we don’t know everything about what it means to be asleep, and to know that we have slept. “We’re going back to it and seeing that it’s actually pretty real,” Andrillon said. “We have just been overlooking this aspect of sleep.”
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