September 20, 2005Remedy for Sleep Apnea May Lift Depression's Veil
By NICHOLAS BAKALAR
Fatigue, irritability, lack of concentration and loss of interest in enjoyable activities are common symptoms of depression. But they are also symptoms of obstructive sleep apnea, and a new study suggests that physicians may confuse the two. The findings, published in the September issue of the journal Chest, reports that many patients with depression symptoms improved markedly when treated with continuous positive airway pressure, or CPAP (pronounced SEE-pap) therapy, the standard treatment for sleep apnea.This finding does not necessarily apply to all patients with depression, said Dr. Daniel J. Schwartz, the lead author on the study and director of the Sleep Center at University Community Hospital in Tampa, Fla.And, Dr. Schwartz said, not everyone who has depression symptoms should automatically be evaluated for a sleep disorder. "But they perhaps should speak with their physicians about symptoms which might be suggestive of obstructive sleep apnea," he said.The disorder, often referred to as O.S.A., occurs when the tongue or throat muscles relax too much during sleep and block the airway. This can happen more than 50 times an hour during sleep, causing snoring and pauses in breathing that last as long as 60 seconds. The problem is twice as common in men, and it afflicts more than 12 million Americans, according to the National Institutes of Health.Sleep apnea is usually treated by wearing a mask or using a specially designed nasal device that delivers air under slight pressure, keeping the airway open so that the patient can breathe normally.Dr. Eric Hollander, professor of psychiatry at Mount Sinai in New York, found the results intriguing. "It might be a real effect on the emotional and physiological symptoms of depression," he said, "and the effect seemed to be pretty robust."The researchers studied 50 men and women admitted to the Tampa sleep center. Each was administered a commonly used psychological screening questionnaire, and 41 showed some signs, either marked or mild, of clinical depression.Nineteen participants had been receiving antidepressant medication for at least two months at the time of referral. After receiving treatment for sleep apnea for four to six weeks, 40 of the 41 participants taking antidepressants and those not taking them showed decreases in their depression scores.They also showed marked improvement in measures of daytime sleepiness.Dr. Steven P. Roose, professor of clinical psychiatry at Columbia University, minimized the importance of the findings.He said the scores on the questionnaire administered at the outset of the study suggested that these patients were not truly clinically depressed to begin with. "Essentially," he said, "the study shows that people who are really not depressed before are really not depressed after" treatment for obstructive sleep apnea.Although the authors assert that their findings strongly support the potential for CPAP to improve the symptoms of depression, they acknowledge that their study has certain limitations. They did not strictly monitor the treatment, and they concede that the questionnaire they used was designed as a screening tool for depression, not for measuring changes in symptoms. They add that they cannot rule out the possibility of a placebo effect from the treatment.Some participants in the study were probably simply misdiagnosed with depression, the researchers concluded, but they pointed out that the misdiagnosis was not always the problem. It may be that the underlying mechanisms of depression and sleep apnea are the same, or that obstructive sleep apnea is itself a cause of depression.The apnea and the depression may simply tend to occur together, Dr. Schwartz said, or there may be "a more complex interaction with one entity contributing to the development of the other.""I regret to say that as yet the answer eludes us," he said.