The Correlation Between Sleep-Disordered Breathing and Psychiatry

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.

CASE VIGNETTE

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.

TABLE 1

Clinical spectrum of sleep-disordered breathing

Pathophysiology

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