Sleep-related headache syndromes.

The relationship between sleep and sleep disorders and headache remains unclear. Clinical experience and numerous studies document some sort of relationship, but the exact nature remains understudied and complex. Changes in sleep duration and sleep quality appear to be capable of affecting headaches of different types. Obstructive sleep apnea can cause or exacerbate headaches in a susceptible person. Obstructive sleep apnea also may cause a specific headache when awakening, which is different from migraine or tension headache and disappears after treatment of the sleep and breathing disturbance. Hypnic headache is another type of sleep-exclusive headache that has been proposed. Hypnic headaches are brief, moderately severe, and affect the elderly primarily.