Sleep Apnea Treatment Outcome Suggests Link to Depression

The relationship between depression and obstructive sleep apnea (OSA) is confounded by the shared morbidities of fatigue, sleep problems, difficulty concentrating, and irritability. As a result experts are unsure whether depression is an authentic problem among OSA patients or a manifestation of the sleep disorder itself.

Now a new study, headed by Daniel Schwartz, M.D., director of the Sleep Center at University Community Hospital in Tampa, shows that depression in OSA patients can be reversed by routine treatment for OSA. A report of the study appears in the September Chest (the journal of the American College of Chest Physicians).

OSA occurs when the tongue and soft tissues of the pharynx block the airway. Continuous positive airway pressure (CPAP) acts as a pneumatic stent keeping the airway open. Untreated, OSA can lead to high blood pressure, weight gain, headaches, impotence, stroke, and right heart failure. Twelve million Americans have OSA, and it is twice as common in men.

In the Tampa study 50 patients referred for evaluation of OSA who had a respiratory disturbance index score equal to or greater than 15, which dropped to half that or less after overnight CPAP, were evaluated for depression using the Beck Depression Inventory (BDI), then tested again after four to six weeks of unsupervised CPAP treatment at home.

Forty-one participants showed marked or mild clinical depression. Nineteen had been receiving antidepressants for at least two months at referral. After home CPAP treatment, 40 of the 41 participants had marked decreases in their BDI scores, regardless of whether they were taking an antidepressant. In addition, all had much less daytime sleepiness.

Schwartz and coworkers William Kohler, M.D., and Gillian Karatinos, M.D., admitted that their study had limitations: the home treatment was not monitored, and the questionnaire they used was more of a screen for depression than an instrument that measured changes in symptoms. Also, the possibility of a placebo effect from the treatment could have influenced the results. And some participants might have been misdiagnosed as depressed.

They believe that the underlying mechanism of both depression and OSA may be the same, or that OSA results in depression. Schwartz suggested the diseases may simply occur together, or there may be a more complex interaction with one contributing to the development of the other.

Psychiatric News asked Melanie Means, Ph.D., a sleep researcher and an associate professor of clinical psychiatry and behavioral sciences at Duke University Medical Center, whether she thinks depression is an authentic problem among OSA patients or a manifestation of the sleep disorder itself. Means said it seems likely that both explanations are accurate.

In a study of changes in depressive symptoms after CPAP treatment for OSA, she found that depressive symptoms experienced by OSA patients are not solely the result of physical OSA symptoms but include a mood component as well. That study appeared in the March 2003 Sleep Breath. Means introduced a hypothetical model to conceptualize the relationship between OSA and depression.

“In some OSA patients, depressive symptoms may reflect a response to the impact of chronic sleep deprivation resulting from OSA. As a chronic medical illness, OSA can result in significant strain in daily functioning, job performance, and social relationships. Over time, these patients may find their coping resources taxed and may develop depressive reactions,” she said.

According to Means, successful treatment of OSA would lead to improved sleep and daytime functioning, with later alleviation of depressive symptoms. But in other OSA patients in whom depression coexists with OSA, depression would not be expected to remit fully after OSA is treated. All of this points to the need for further studies to better understand the relationship between OSA and depression and explore the mechanism of their interaction.

Given the increased incidence of depressive symptoms in OSA, she advised sleep clinicians to evaluate and monitor depression levels in OSA patients before and after treatment. “Because OSA is such a common sleep disorder in the general population, it is also important that all health care providers evaluate for symptoms of OSA in their patients who complain of sleep difficulties and/or excessive daytime sleepiness,” she said.

An abstract of “Symptoms of Depression in Individuals With Obstructive Sleep Apnea May Be Amenable to Treatment With Continuous Positive Airway Pressure” is posted at<www.chestjournal.org/cgi/search?sendit=Search&pubdate—year=2005&volume=128&firstpage=1304&author1=schwartz>.▪