Sleep Misperception - When Being Asleep Feels Like Being Awake

By Ryan Neely, Ph.D.

In the field of sleep science, it is common to observe a mismatch between a person’s experience of sleep and brain measurements used by researchers to determine what state of wakefulness or sleep that person was in. This mismatch is referred to as “sleep state misperception,” and it is not only common, but the difference between reported sleep and measured sleep can be substantial. Some individuals will present to a clinic complaining that they “haven’t slept in months,” only to display normal sleep patterns when observed in a sleep laboratory. These observations raise important questions about how we objectively define healthy and disordered sleep, and what matters when considering the impact of interventions intended to improve sleep quality. 

How common is sleep state misperception, and how does it manifest?

Sleep state misperception, also known as subjective-objective sleep discrepancy, is a difference between sleep reported by an individual and sleep as measured by polysomnography. Polysomnography, or PSG, is a suite of sensors that measure brain, muscle, respiratory, and cardiac parameters, and is considered the “gold standard” for measuring sleep. Typically, discrepancies between reported sleep and PSG are found in estimates of total sleep time (TST), sleep onset latency (SOL, the amount of time it takes to fall asleep initially), and wake after sleep onset (WASO, periods of waking up in the middle of the night). On average, healthy sleepers tend to correctly estimate their total sleep time, but even in this population, people can overestimate or underestimate by several hours. In contrast, insomnia sufferers tend to significantly underestimate their total sleep time, with some individuals underestimating it by 8 hours or more1. Extreme cases of sleep state misperception are known as paradoxical insomnia, in which sufferers do not experience daytime sleepiness and display normal sleep patterns, but still report feeling awake for large portions of the night. Between 9 and 50% of insomnia patients may actually be experiencing paradoxical insomnia2. In general, insomnia sufferers typically report worse sleep estimates than measured by PSG. On average, insomnia patients were found to underestimate total sleep time by 13 ± 94 minutes, and overestimate the time it took them to fall asleep by 22 ± 56 minutes3. 

Are misperceivers simply wrong?

At face value, it may seem that someone experiencing sleep state misperception is simply “wrong” about being awake when they are actually asleep. However, the truth may be a bit more complex. The boundary between wakefulness and sleep is actually quite difficult to define objectively, with different studies and different research groups drawing this boundary at different points4. In fact, when it comes to measuring the time it takes to fall asleep, good sleepers overestimate by about 490% on average compared to PSG1. This suggests that the feeling of being asleep doesn’t take hold until well after the brain exhibits signals indicative of sleep onset. Normal sleepers also report feeling awake between 12-19% of the time during stage N2 and N3 sleep, although during REM sleep, this only occurrs 0-3% of the time5,6. These studies suggest that the tools we have to measure sleep may not be sufficient to fully capture what is happening in the brain that produces feelings of being asleep. Still, the fact that insomnia sufferers report a consistent bias towards underestimating total sleep time while healthy sleepers do not suggest that there is something else going on in the brain of these individuals. 

What explains sleep state misperception?

A number of studies have attempted to discover neurological correlates of sleep state misperception. To date, the results have been mixed: some studies have found no significant differences in sleep structure between healthy sleepers and paradoxical insomniacs6,7, while others did find differences in N1 and N2 duration8. These inconsistent results suggest typical PSG-based measurements may not capture the features of sleep misperception. Studies utilizing different tools have yielded new clues into this phenomenon. For example, Kay and colleagues looked at glucose metabolism (a marker of energy use) in the brains of insomnia patients compared to healthy sleepers. They found changes in metabolism across different brain regions, suggesting that insomniacs may have elevated brain activity in certain areas that are difficult to detect with other methods9. Other research has suggested that individual brain circuits can “flicker” between wake and sleep states independently, suggesting that sleep may be a much more regional phenomenon than initially thought10. These and other data support the notion that insomnia sufferers may indeed be experiencing wakefulness, just in a way that is difficult to detect with standard methods. 

What can be done about sleep misperception?

As explored in an earlier blog post, insomnia as a clinical phenomenon is defined subjectively - meaning the experience and impairment of the patient is what determines the diagnosis, regardless of any objective measurements. This means that the symptoms of insomnia are treated regardless of whether they can be detected in a sleep laboratory or not. In general, sleep misperception itself is not harmful unless it is causing distress or impairment. However, concerns about inadequate sleep can cause distress in some people that can lead to objective sleep disturbances12. Any intervention that produces the perception of improved or more consistent sleep can help reduce this type of stress. Additionally, data suggests that there may be many subtypes of insomnia, and sleep misperception may define one such subtype11. Using new tools to understand the etiology, or underlying causes, of sleep misperception may lead to better treatment of this type of insomnia. Finally, the increasing availability of sleep tracking tools, especially those like Elemind’s that measure brain activity during sleep, can help us better understand this phenomenon outside of laboratory settings and in the population at large. These approaches can help to reconcile the discrepancy between reported and measured sleep metrics, and possibly find new ways to help people feel better about their sleep. 

References cited:

1. Stephan, A.M. and Siclari, F., 2023. Reconsidering sleep perception in insomnia: from misperception to mismeasurement. Journal of Sleep Research, 32(6), p.e14028.
2. Rezaie, L., Fobian, A.D., McCall, W.V. and Khazaie, H., 2018. Paradoxical insomnia and subjective–objective sleep discrepancy: A review. Sleep medicine reviews, 40, pp.196-202.
3. Valko, P.O., Hunziker, S., Graf, K., Werth, E. and Baumann, C.R., 2021. Sleep-wake misperception. A comprehensive analysis of a large sleep lab cohort. Sleep Medicine, 88, pp.96-103.
4. Ogilvie, R.D., 2001. The process of falling asleep. Sleep medicine reviews, 5(3), pp.247-270.
5. Feige, B., Nanovska, S., Baglioni, C., Bier, B., Cabrera, L., Diemers, S., Quellmalz, M., Siegel, M., Xeni, I., Szentkiralyi, A., & Doerr, J. P. (2018). Insomnia – perchance a dream? Results from a NREM/REM sleep awakening study in good sleepers and patients with insomnia. Sleep, 41(5), 1–11.
6. Stephan, A. M., Lecci, S., Cataldi, J., & Siclari, F. (2021). Conscious experiences and high-density EEG patterns predicting subjective sleep depth. Current Biology, 31(24), 5487–5500.e3.
7.  St-Jean, G., Turcotte, I., Pérusse, A. D., & Bastien, C. H. (2013). REM and NREM power spectral analysis on two consecutive nights in psychophysiological and paradoxical insomnia sufferers. International Journal of Psychophysiology, 89(2), 181–194.
8.  Andrillon, T., Solelhac, G., Bouchequet, P., Romano, F., Le Brun, M. P., Brigham, M., Chennaoui, M., & Leger, D. (2020). Revisiting the value of polysomnographic data in insomnia: More than meets the eye. Sleep Medicine, 66, 184–200.
9. Kay DB, Karim HT, Soehner AM, Hasler BP, James JA, Germain A, Hall MH, Franzen PL, Price JC, Nofzinger EA, BuysseDJ.  Subjective-objective discrepancy is associated with alterations in regional glucose metabolism in patients with insomnia and good sleeper controls. Sleep 2017;40:doi.org/10.1093/sleep/zsx155/4282628 
10. Parks, D.F., Schneider, A.M., Xu, Y., Brunwasser, S.J., Funderburk, S., Thurber, D., Blanche, T., Dyer, E.L., Haussler, D. and Hengen, K.B., 2024. A nonoscillatory, millisecond-scale embedding of brain state provides insight into behavior. Nature neuroscience, pp.1-15.
11. Edinger J D and Krystal A D 2003 Subtyping primary insomnia: is sleep state misperception a distinct clinical entity? Sleep Med. Rev. 7 203–14
12.  Harvey AG, Tang NK. (Mis) perception of sleep in insomnia: A puzzle and a resolution. Psychol Bull 2012;138(1):77–101