ANN ARBOR, MICH--Patients with cluster headaches frequently have undiagnosed sleep-disordered breathing, a recent study has found.[1]

"The key implication of the study is that physicians should consider the possibility of obstructive sleep apnea in patients with cluster headaches because sleep-disordered breathing appears to be common in these patients," Ronald D. Chervin, MD said in an interview with RESPIRATORY REVIEWS. "Preliminary evidence suggests that treating obstructive sleep apnea can improve symptoms in patients with cluster headaches," he added.

Dr. Chervin and colleagues in the Sleep Disorders Center of the University of Michigan in Ann Arbor conducted an observational study to evaluate patients with active or inactive cluster headaches for occult sleep-disordered breathing. Before the start of the study, none of the 25 subjects had been given a diagnosis of sleep-disordered breathing. The researchers performed polysomnography on all subjects, and they monitored end-tidal carbon dioxide and esophageal pressure in 22 and 20 patients, respectively.

Eighty percent of subjects were found to experience more than five episodes of apnea and hypopnea per hour of sleep, and 44% had 10 or more of these events per hour. Minimum oxygen saturation was less than 90% in 10 subjects. Maximum negative esophageal pressure ranged from -13 to -65 cm H2O, and the maximum end-tidal carbon dioxide level was 50 mm Hg or higher in eight subjects. Patients who reported that their cluster headaches typically occurred in the first half of the nocturnal sleep period had more severe oxygen desaturation than did the subjects whose headaches started later.

DECREASED CO2 RESPONSE

The researchers also found that patients with active cluster headaches had significantly higher maximum end-tidal carbon dioxide levels than did those whose cluster headaches were inactive during the study. "It is possible that a decreased responsiveness to carbon dioxide may trigger headaches," suggested Dr. Chervin, an Assistant Professor of Neurology at the University of Michigan. However, he pointed out, "our study showed that minimum oxygen saturation was the only thing that was independently related to the timing of cluster headache."

Several abrupt physiologic changes occur in patients with sleep-disordered breathing that may play a role in cluster headaches, including hypercarbia and hypoxemia, as well as alterations in autonomic tone, Dr. Chervin suggested. "It's also possible that the repetitive, large, negative intrathoracic pressures that occur during sleep apnea may indirectly affect intravascular content and the vessels in the head," he added. "But these hypotheses are all speculative."

Whether sleep-disordered breathing causes cluster headaches is unclear. "This study only determined that many patients with cluster headaches also have sleep-disordered breathing. It did not establish a causal relationship. In fact, it is entirely possible that there is a third variable that is responsible for both obstructive sleep apnea and cluster headaches," Dr. Chervin noted. "The next step should be to identify people with cluster headaches and obstructive sleep apnea and test the hypothesis that treating sleep apnea improves headaches," he said.

--Deborah L. O'Connor

Reference
1. Chervin RD, Zallek SN, Lin X, et al. Sleep disordered breathing in patients with cluster headache. Neurology. 2000;54:2302-2306.