With increasing knowledge about sleep and its disorders and widespread use of diagnostic testing for sleep, more patients with sleep-disordered breathing (SDB) are being identified. Various comorbid medical, neurological, and psychiatric disorders are more prevalent in patients with clinically significant SDB. This article explores the relationship between SDB and psychiatric disorders and its implication for practicing psychiatrists.
Alex is a 58-year-old married, certified public accountant who snores loudly and has frequent nocturnal awakenings, sometimes with gasping or choking. He generally goes to bed at midnight and wakes up at 6:30 am. On weekends, he usually sleeps 1 or 2 hours longer and sometimes takes a 1-hour nap.
He gained 12 lb in the past year but is not obese (his BMI is 28.5). He reports increasing back pain, fatigue, irritability, and cognitive problems. He occasionally feels anxious and moody, especially when his aches and pains are exacerbated. Six months ago, nocturia developed, but prostate-specific antigen (PSA) test results were normal. At that time, he also began having morning dry mouth, morning headaches, sadness, tiredness, and generally depressed mood. Treatment with an SSRI was initiated; he also had a brief trial with methylphenidate.
He was referred for polysomnography, which revealed severe obstructive sleep apnea with significant oxyhemoglobin desaturations occurring during REM sleep. There were also some central-type SDB events. The patient was treated with bilevel positive airway pressure, with good effect.
This case illustrates a fairly common story. When a middle-aged man becomes less active, works at a sedentary job, gains weight, and begins to snore, chances are that he has or is developing SDB. Job demands and family responsibilities promote sleep schedule restriction, often prompting increased caffeine intake. Nonetheless, sleepiness, tiredness, and fatigue almost invariably follow. Obvious signs include fatigue, attention problems, less effective coping, and depressed mood. A patient may recognize cognitive dulling, as in this case.
Less obvious symptoms include nocturia, morning headache, and difficult to control pain. Our training dictates that we immediately suspect prostate disease when nocturia develops. However, the negative intrathoracic pressure created by attempting to inhale against an occluded airway provokes release of atrial natriuretic peptide, especially during REM sleep. The resulting nocturia is often periodic, occurring at 1- to 2-hour intervals, with minimal voiding; PSA test results are normal.
The negative intrathoracic pressure also creates afterload on the heart and may be associated with increased levels of inflammatory cytokines. Morning headaches can be provoked by hypoxemia during REM-related SDB. REM sleep episodes become progressively longer during the sleep period, and obstructive SDB is usually more severe during REM sleep. In patients who smoke cigarettes or who have a history of smoking, lung function declines more quickly as a function of age. In patients with SDB, severe hypoxemia can result. Sleep loss and pain coexist in a vicious circle: sleep loss lowers pain threshold and pain disrupts sleep. Sedative hypnotics to promote sleep and opioid analgesics reduce respiratory drive, raise arousal threshold, and generally worsen SDB. The net result is greater sleep disruptions and continued pain.
SDB includes a wide spectrum of disorders that manifest as compromised breathing during sleep (Table 1). At one end of the spectrum is primary snoring, ie, snoring without any daytime symptoms or clinically significant reduction in the inspiratory flow. At the other extreme is obstructive sleep apnea, a serious, chronic, and sometimes debilitating condition. SDB also includes cen-tral sleep apnea and sleep-related hypoventilation.
What is already known about sleep-disordered breathing (SDB) and the correlation with psychiatry?
? Psychiatric medical conditions, particularly depression and anxiety, are common in patients with SDB. Multiple mechanisms are proposed to explain this relationship.
What new information does this article provide?
? Sleepiness and impaired coping mechanisms link SDB, depression, and anxiety disorders. More proactive case findings and SDB treatment in patients with depression and anxiety may help improve management of the psychiatric condition. However, some psychiatric medications can adversely affect sleep and breathing.
What are the implications for psychiatric practice?
? SDB signs and symptoms overlap with mood, anxiety, and other psychiatric illnesses. In some cases, they may masquerade as these disorders, but SDB can also provoke and/or exacerbate other psychiatric conditions. In addition to obvious symptoms in at-risk populations, SDB should be considered in menopausal women in whom insomnia and fatigue have recently developed and in children who snore and have attention problems. Some screening tools and evaluation techniques in psychiatric practices may help identify the SDB at-risk population.
Obstructive types of the sleep-related breathing disorders involve narrowing and flow limitation in the upper airway. During inhalation, this can lead to collapse (apnea), partial collapse (hypopnea), or increased resistance. As airway resistance increases, the effort to breathe and the work of breathing increase. If the effort to breathe increases past some threshold or if the airway collapses, a CNS arousal ultimately occurs, returning ventilation to voluntary control so that the airway can be dilated and breathing can resume. This process is often accompanied by cascading snores, possibly followed by a period of silence (that may persist for several seconds to more than 1 minute), and finally an explosive breath (with possible snorting, gasping, and/or coughing). The patient may quickly fall back to sleep and resume snoring, possibly repeating this sequence hundreds of times during the night.
Table 2 lists risk factors, common symptoms, and clinical features of SDB. Many consequences of SDB are also common psychosomatic symptoms. In this case, however, the etiology is well documented and the problem diminishes or disappears when the sleep-disordered breathing is treated.
Various questionnaires are available to help identify persons at high risk for SDB. One such questionnaire is the STOP BANG questionnaire that can be used in clinical practice.1
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