here has been a link between the cyclical variation of cluster headache and chronic paroxysmal hemicrania, a certain type of one-sided headache, to the REM sleep cycle.

Research has suggested that certain headache disorders are associated with different patterns of sleep disturbance, which may influence the response of treatment.

Cluster headaches are one-sided severe headache attacks that are usually accompanied by nasal stuffiness and eye tearing, and frequently occur during the nighttime. There has been an association of these attacks to REM sleep and research has noted an increase of sleep apnea in patients who experience cluster headaches.

In patients with cluster headaches who have sleep apnea, it is suggested that they may be experiencing an episodic decrease in oxygen during the night that can precipitate the headache attacks. In patients who have chronic cluster headaches, it is noted that two-thirds of the attacks usually occur during the last two hours of sleep.

In fact, in one report, patients who have cluster headaches and sleep apnea were also noted to have experienced bed-wetting and night terrors during childhood.