Can’t Sleep?

You May Have Sleep Apnea!

In this issue of CHEST (see page 1923), Krakow et al examine the prevalence of symptoms of insomnia in patients with sleep-disordered breathing. In this retrospective analysis from their university sleep-disorders laboratory, they found that 50% of those studied had insomnia symptoms. Insomnia symptoms were defined as a yes answer to two or more of three questions, including: (1) does it take > 30 min to fall asleep? (2) do you wake up a lot? or (3) if awakened, is it difficult returning to sleep? Their findings complement an earlier report¹ studying older adults with insomnia, who had a prevalence of obstructive sleep apnea (OSA) ranging from 29 to 43%, depending on the apnea-hypopnea index (AHI). Although better designed studies are needed to confirm these findings, they do raise an important issue concerning our approach to patients with these disorders. Despite the fact that sleep apnea is listed in the differential diagnosis of insomnia in the textbook, Principles and Practice of Sleep Medicine,² clinicians are taught that most patients with insomnia do not need polysomnography. Moreover, the majority of insurance companies will not pay for a sleep study if it is ordered as part of an insomnia evaluation. The findings of Krakow et al suggest this position may need review.

Sleep apnea is typically described as a disorder of excessive daytime sleepiness, but not all patients with sleep apnea demonstrate hypersomnia. Some patients complain of chronic fatigue rather than “sleepiness.” We may not be asking the correct historical questions to detect sleep apnea in patients without hypersomnia. Or, even worse, we may not consider sleep apnea in the differential diagnosis of insomnia at all. What has been described may be a syndrome of “hidden” sleep apnea.

In addition to the role insomnia may play in the diagnosis of sleep apnea, concomitant insomnia may also have an effect on treatment of sleep apnea. My own experience in treating OSA is that continuous positive airway pressure (CPAP) frequently results in difficulty initiating sleep, awakenings for mask displacement, and early morning awakenings with an inability to return to sleep with the apparatus on—in other words, more awakenings at night. Indeed, it has been shown that women are less compliant with CPAP and, as is well-known, women have substantially more insomnia.³ Perhaps a lower arousal threshold and difficulty initiating and maintaining sleep, in part, contribute to this phenomenon of decreased compliance to CPAP in this situation. Many patients with insomnia have concomitant psychiatric disorders and anxiety. From 25 to 40% of insomniacs have anxiety complaints. This may also play a role in CPAP compliance. Anxious patients may be more likely to have more claustrophobic symptoms that may impede CPAP usage. Depression and feelings of worthlessness frequently associated with insomnia may also hinder attempts at treatment regimens.

Treatment of insomnia can be very difficult. Most experts advocate cognitive behavioral therapy with or without adjunctive pharmacologic intervention. Unfortunately, the medications used for insomnia may have adverse effects on sleep apnea. The available literature suggests that hypnotics such as triazolam, zolpidem, and zaleplon are relatively safe in patients with moderate COPD, but whether this observation can be extrapolated to patients with sleep apnea is unclear.⁴ Triazolam has been shown to increase the non-rapid eye movement apnea-hypopnea index (AHI) and result in lower oxygen saturation in a group of patients with moderate OSA.⁵ However, another study⁶ examining temazepam in elderly insomniacs with mild sleep apnea (mean AHI < 10) did not show a worsening of their OSA with drug. It is also possible that consistent use of these drugs may alter CPAP requirements, although alcohol, a drug known to worsen OSA, did not in one study.⁷ At any rate, given the uncertainties of the effects of these drugs in patients with insomnia and OSA, their use should be initiated with caution.

Finally, the study raises questions as to how well pulmonologists are at diagnosing and treating insomnia. Formalized sleep medicine training has been slow to develop in pulmonary fellowship programs, and often little attention is given to the teaching of sleep and its disorders in medical schools.⁸ As Krakow et al note in their article, although most pulmonologists are adept at treating OSA, adequate expertise to treat insomnia may be lacking. There is a need for more comprehensive sleep training in pulmonary fellowship programs to adequately prepare pulmonologists to treat patients with sleep disorders other than OSA.

In conclusion, the findings of Krakow et al should heighten the awareness of practitioners evaluating both sleep apnea and insomnia complaints, and prompt further study of both disorders. It also highlights the need for more comprehensive training of pulmonologists in sleep medicine.