Is Insomnia a Disease or a Symptom?

Abstract & Commentary

By Barbara A. Phillips, MD, MSPH, Professor of Medicine, University of Kentucky; Director, Sleep Disorders Center, Samaritan Hospital, Lexington. Dr. Phillips serves on the speakers bureau for PotomaCME.

Synopsis: In this small pilot study of patients who sought help for insomnia, most of the awakenings were actually caused by sleep-disordered breathing.

Source: Krakow B, et al. Prospective assessment of nocturnal awakenings in a case series of treatment-seeking chronic insomnia patients: A pilot study of subjective and objective causes. Sleep 2012;35:1685-1692.

These authors set out to learn what makes people with insomnia wake up at night. To address this problem, they prospectively recruited patients who sought initial sleep evaluation at Maimonides Sleep Arts and Sciences, in Albuquerque, New Mexico, but had not previously done a sleep study. To be included in this study, candidates listed insomnia as their primary sleep complaint, scored at least 15 on the Insomnia Severity Index (ISI),1 reported sleep-related impairment, met research criteria for an insomnia disorder, completed an Internet-based intake survey, spoke English, and were at least 18 years old. During the 22-month period of data collection, 512 patients presented with complaints of insomnia, but only 20 met the inclusion criteria and completed the study. This study group completed several sleep-related questionnaires as well as questionnaires about depression and insomnia. They also underwent histories and physical examinations, and participated in pre-sleep interviews during which they were asked about sleeping difficulties and what they perceived to be the cause of problems going to sleep, staying asleep, or waking up at night. They then underwent sleep studies (polysomnograms). About a week after the sleep studies, the patients returned for follow-up interviews, during which they went over the data from their sleep studies and were asked about their perceptions of reasons for wakenings.

All 20 patients in this study reported difficulty staying asleep, but most (17) also had difficulty going to sleep. About half of the patients reported that they were snorers. As is fairly common in patients with insomnia, their self-reported sleep quality was worse than what was actually measured. For example, their average reported sleep efficiency (the amount of time in the bed that is actually spent sleeping) was lower than their measured sleep efficiency (they estimated they slept 60% of the time, but their measured sleep efficiency was actually about 81%; normal is 85%). Similarly, they estimated that they slept about 5 hours in the laboratory, but the average measured sleep duration was about 6 hours. They also significantly overestimated both how long it took them to fall asleep and how much time they spent awake once they had fallen asleep. On clinical interviews, a majority of patients reported that worries and stress were they main things that woke them up or kept them from falling asleep. Nocturia was given by the patients as the second most common cause of sleep disturbance (after psychological factors). About 15% of the sample listed pain as a factor in sleep disturbances. No patients in this sample reported breathing difficulties as a contributor to their sleeping difficulties.

With regard to objective scoring of sleep studies, 531 awakenings from sleep were scored in the 20 sleep studies, with an average of about 27 awakenings per study (normal is about 8). Of these awakenings, 90% were triggered by a respiratory event. The rest were spontaneous or resulted from laboratory equipment. A majority of the respiratory events (78%) were respiratory effort-related arousals, 20% were hypopneas, and about 2% were frank apneas. The mean duration of respiratory-triggered awakenings was about 25 minutes. The number of respiratory events correlated strongly with the insomnia severity index score, although the Pearson correlation coefficients were not statistically significant. Using standard definitions for sleep apnea, more than half (11/20) met criteria for sleep apnea, and the rest met criteria for upper airways resistance syndrome. In a second analysis, the authors learned that, while most awakenings were precipitated by breathing events, only a small proportion of those breathing events led to awakenings.

In post-sleep study interviews, most (17/20) of the patients accepted that sleep-disordered breathing could be contributing to their sleeping difficulty. In fact, 12 of the patients underwent treatment for sleep-disordered breathing (seven with oral appliances and five with Continuous Positive Airway Pressure, aka CPAP). Unfortunately, the effects of these treatments on their insomnia symptoms is not reported in this paper.

Commentary

Insomnia is a prevalent, distressing, and refractory symptom, and primary care practitioners are on the front lines in managing it. Increasingly, emphasis has shifted from pharmacologic management of insomnia to cognitive behavioral therapy (CBT). This change in management is driven by several factors, including better efficacy of CBT than hypnotics for chronic insomnia. Although hypnotics may provide initial subjective improvement, their long-term efficacy is inferior to that of CBT. Perhaps the most important factor driving abandonment of pharmacologic treatment of chronic insomnia is the increasingly robust association between chronic use of sleeping pills and a variety of adverse outcomes, including cancer, car crash, death, and heart disease.3-7

It is important to keep in mind that both the studies that associate sleeping pills with adverse outcomes and the studies that associate insomnia with adverse outcomes do not prove causality. However, since we can’t randomize patients to be insomniacs or not, such cross-sectional data will have to do, for now. However, the vast majority of studies that purport to demonstrate that either insomnia or use of sleeping pills is harmful have failed to control for the fact that insomniacs are unhealthy people in general (and thus more likely to die). For example, they are more likely to be obese, smoke, and have medical and psychiatric illness.5,6 And, as the current study suggests, they may be more likely to have sleep-disordered breathing, which is a well-established risk factor for car crash, cardiovascular disease, and death.

What does this mean for the practitioner who is grappling with a real, live insomniac? Perhaps the first message is that sleeping pills are not the immediate, best response. Insomnia means something, but the current (albeit small) study suggests that it may be a symptom, rather than a primary condition. Mood disturbance, especially depression and anxiety, are strongly associated with insomnia, and we know to consider and possibly treat these conditions in patients with sleep complaints. But now there is a new kid on the block to consider in the patient with chronic insomnia: sleep-disordered breathing. And we have another possible explanation for why insomniacs may have adverse outcomes.

References

1. Bastien CH, et al. Validation of the Insomnia Severity Index as an outcome measure for insomnia research. Sleep Med 2001;2:297-307.

2. Morin CM, Benca R. Chronic insomnia. Lancet 2012; 379:1129-1141.

3. Gustavsen I, et al. Road traffic accident risk related to prescriptions of the hypnotics zopiclone, zolpidem, flunitrazepam and nitrazepam. Sleep Med 2008;9:818-822.

4. Mallon L, et al. Is usage of hypnotics associated with mortality? Sleep Med 2009;10:279-286.

5. Kripke DF, et al. Hypnotics’ association with mortality or cancer: A matched cohort study. BMJ Open 2012; 27:e000850.

6. Phillips B, Mannino D. Correlates of sleep complaints in adults: The ARIC study. J Clin Sleep Med 2005;1: 277-283.

7. Vozoris NT, Leung RS. Sedative medication use: Prevalence, risk factors, and associations with body mass index using population-level data. Sleep 2011;34:869-874.