Sleep-related breathing disorders and headache.

Obtructive sleep apnoea syndrome (OSAS) is a common disorder in the general population with an estimated prevalence in an adult population of 2% in women and 4% in men. Although several studies have suggested that headaches, particularly morning headaches, are more common in patients with OSAS than in normal subjects, others have yielded contradictory findings. When the sleep-related breathing disorder was treated with success, the headache generally disappeared, supporting a causal role of the sleep disorder for headache. Several hypotheses have been proposed to explain the relationship between OSAS and the occurrence of headache, particularly on awakening. Night-time fluctuations of oxygen saturation during the night with hypercapnia, vasodilatation, increased intracranial pressure and impaired sleep quality are all considered contributing factors. However the exact mechanisms of headache pathogenesis and the relationship between OSAS, headache and morning headaches in particular remain controversial.