Estimates are that 50 to 70 million Americans suffer from a chronic disorder of sleep and wakefulness, hindering daily functioning and affecting health.1 Psychiatric illness is common among people who have a sleep disorder. The relationship between psychiatric illness and sleep disorders is bidirectional: People with mental illness often have sleep complaints, and a primary sleep disorder often results in neuropsychiatric complications.
What is obstructive sleep apnea?
The most common type of sleep-disordered breathing, obstructive sleep apnea (OSA) is characterized by frequent cessations of breathing during sleep because of an obstruction of the upper airway. The obstruction occurs secondary to inadequate motor tone of the tongue or airway dilator muscles, or both.1 In addition, many people with OSA have central apneic episodes, in which breathing stops temporarily without airway blockage or respiratory effort.2
The prevalence of OSA is growing as obesity in the United States increases. Risk factors for OSA include obesity, a craniofacial abnormality, an upper-airway abnormality, heredity, smoking, and nasal congestion. OSA plays a role in causing and exacerbating medical illness in people with severe and persistent mental illness, contributing to a significantly shortened life span. Attending to the general health of people who suffer from severe mental illness—including effective treatment of illnesses such as OSA—is crucial.3
Clinical features of OSA
OSA is characterized by hypopnea (a decrease in breathing during sleep) or apnea (an actual pause in breathing). Pauses in breathing during sleep of at least 10 seconds, with obstruction of oronasal airflow despite continuous chest and abdominal movements, are referred to as obstructive apneas. These pauses are associated with a decrease in oxygen saturation or arousal from sleep, or both.1
Primary features of OSA include sleep fragmentation accompanied by nocturnal hypoxemia and hypercapnia, with resulting excessive daytime sleepiness, mood problems, and poor neurocognitive performance (Table 1). OSA often causes potentially serious organ system dysfunction, including adverse cardiovascular and metabolic effects. Studies have suggested that executive dysfunction can be a feature of OSA, which is thought to be related to prefrontal lobe dysfunction caused by intermittent hypoxia. All of these conditions can contribute significantly to decreased quality of life.1
The prevalence of OSA in the general population is approximately 20% when the condition is defined as an apnea-hypopnea index >5 events an hour. The index is the number of apnea and hypopnea episodes that occur during 1 hour of sleep.4
OSA and psychiatric illness
Psychiatric disorders often are comorbid with OSA. These include depression, anxiety, bipolar disorder, schizophrenia, posttraumatic stress disorder (PTSD), panic disorder, and substance use disorder.
Depression. Several studies have documented that OSA and depressive disorder often are comorbid. Many symptoms are common to both, including fatigue, daytime sleepiness, poor concentration, irritability, and weight gain (Figure), although some core symptoms of depression (eg, sadness, anhedonia, guilt, and agitation) are clearly distinguishable from symptoms of OSA. The current recommendation is that a mood disorder should be considered secondary to OSA, and treated accordingly.5
Anxiety. OSA also has been linked to anxiety and nocturnal panic attacks. Frequent awakening due to choking from breathing cessation might play a role in the development of anxiety in patients with OSA, although the association is unproven. Studies have shown a correlation between anxiety disorders and excessive daytime sleepiness, one of the core symptoms of OSA.6 OSA is highly prevalent among combat veterans who have PTSD and complain of being overly vigilant at night; experiencing nightmares and frequent awakening; and having non-restorative sleep.7 Anecdotal reports suggest an association between OSA and bipolar disorder: namely, that continuous positive airway pressure (CPAP) treatment (see “How is OSA treated?,” below) might switch depressed patients to mania.8
Schizophrenia. A strong association exists between OSA and schizophrenia. In a study,9 an OSA diagnosis was made 6 times more often in patients with schizophrenia than in patients with other psychiatric illnesses. Obesity, male sex, and chronic antipsychotic administration were risk factors for OSA in patients with
schizophrenia.9 OSA might be underdiagnosed in patients with schizophrenia because excessive daytime sleepiness, the most common daytime symptom of OSA, can be misattributed as a negative symptom of the disease or a side effect of pharmacotherapy.
OSA and medical illness
OSA can be comorbid with several medical conditions (Table 2). Sleep research in the past 15 years has demonstrated that chronic sleep deprivation has multiple untoward health consequences apart from excessive daytime sleepiness.10 Recent research suggests that chronic sleep loss (<7 hours a night), including sleep loss secondary to OSA, has wide-ranging effects on the cardiovascular, endocrine, immune, and nervous systems, including: