The patient suffers from paradoxical insomnia: the discrepancy between estimated sleep time and objective sleep time calculated on PSG (supported, in this case, by the results of actimetry) and the lack of daytime consequences of the drastic sleep loss reported by the patient are the essential features of this insomnia subtype.

PSG analysis shows an objective total sleep time of 8 hours, while the patient reported an estimated sleep time that night of less than one hour. Additionally, actigram consistently shows nocturnal sleep periods of 8 hours or longer (highlighted in red).

Discussion

"Paradoxical insomnia" is a primary insomnia subtype introduced in the revised International Classification of Sleep Disorders in 2005 to replace the former "Sleep State Misperception" category.¹ Paradoxical insomnia is characterized by a discrepancy between subjective sleep time and objective sleep evaluated by polysomnography (PSG) or actimetry, constant rumination and/or awareness of external stimuli during the night and a level of daytime impairment inconsistent with the reported sleep deprivation. Overestimation of sleep latency and wake after sleep onset and underestimation of total sleep time are common in most insomniacs, but in patients with paradoxical insomnia, the discrepancy between subjective and objective sleep is far greater.² In the absence of adequate general population studies and given the variability in clinic-based study results, the prevalence is difficult to ascertain² but it is probably low, paradoxical insomnia affecting less than 5% of insomniacs.¹

In our patient, all ICSD-2 diagnostic criteria were present, although we were not able to convince the patient to keep a sleep diary. Because of the extreme sleep loss reported by the patient, the absence of daytime impairment and of symptoms suggestive of another type of insomnia, polysomnography and actimetry were recommended. Their results supported the initial clinical impression of sleep state misperception. Differential diagnoses include malingering and, particularly when the mismatch between subjective and objective measurements of sleep is less marked than in our patient, other types of primary insomnia such as psychophysiological or idiopathic insomnia.

Little is known about the mechanisms underlying sleep misperception. Although conventional sleep staging is not significantly different in normal sleepers and paradoxical insomniacs, more subtle abnormalities (stage 2 and 3 spectral measures, cyclic alternating patterns and arousals) have been reported and may contribute to the patient’s sensation of unrefreshing sleep, delayed sleep onset and increased WASO.^2-5 Our patient indeed had several brief awakenings and the arousal index was relatively high (Image 1, Table). No clear cause for this sleep fragmentation could be established. There was no significant respiratory abnormality or periodic limb movements.

The patient was seen again in clinic to discuss the results of the PSG and the actimetry. She was relieved by our explanations and a follow-up visit was scheduled 6 months later. However, in our experience as well as others,² some patients tend to be exceedingly dissatisfied with the diagnosis and blame PSG results on faulty sensors or incompetent sleep technologists. In such patients, relief of paradoxical insomnia is often difficult to achieve.

There are currently no guidelines regarding treatment options. Rather than improving sleep habits or prescribing a course of sedative medication, improving sleep perception through cognitive behavioral therapy may be more effective in these patients^{2, 6-7}. Current published data on comparing various interventions are scant. The management error in these patients is prescribing a sedative hypnotic at bedtime with increasing dosage as was the case in this patient with no improvement on follow-up evaluation, and increasing risk of daytime side effects. Fortunately, our patient had spontaneously discontinued her treatment because of the lack of efficacy.  Objective evaluation of sleep, with actimetry and/or polysomnography should be considered when there is a lack of treatment efficacy in insomnia.

References

1. American Academy of Sleep Medicine. International classification of sleep disorders, ed 2. Westchester, IL: American Academy of Sleep Medicine; 2005.

2. Edinger JD, Krystal AD. Subtyping primary insomnia: Is sleep state misperception a distinct clinical entity? Sleep Med Rev 2003;7:203-214.

3. Smith S, Trinder J. The effect of arousals during sleep onset on estimates of sleep onset latency. J Sleep Res 2000;9:129-135.

4. Parrino L, Milioli G, De Paolis F, Grassi A, Terzano MG. Paradoxical insomnia: The role of cap and arousals in sleep misperception. Sleep Med 2009;10:1139-1145.

5. Turcotte I, St-Jean G, Bastien CH. Are individuals with paradoxical insomnia more hyperaroused than individuals with psychophysiological insomnia? Event-related potentials measures at the peri-onset of sleep. Int J Psychophysiol 2011;81:177-190.

6. Geyer JD, Lichstein KL, Ruiter ME, Ward LC, Carney PR, Dillard SC. Sleep education for paradoxical insomnia. Behav Sleep Med 2011;9:266-272.

7. Tang NK, Harvey AG. Correcting distorted perception of sleep in insomnia: A novel behavioural experiment? Behav Res Ther 2004;42:27-39.

Citation: Launois SH, Fresco JP. Ten years of sleepless nights. Ann Am Thorac Soc 2013;10:67-70.