Headache and sleep.

Headache and sleep have long been recognised as being interdependent due to specific causative factors. Yet, the precise understanding of the roles played by these factors in this interdependency remains elusive. Many observations have suggested a reciprocal relationship between headache and sleep; however, these hypotheses have only been partially substantiated by robust findings. Being so, additional well-designed clinical and laboratory studies are required to confirm these relationships. Nonetheless, sleep and headache are known to be related in several ways: primary headache such as migraine, cluster headache (CH) and hypnic headache (HH) can be triggered by sleep, while chronic morning headaches can be caused by sleep disorders such as sleep apnoea and insomnia. Furthermore, headache and sleep disorders can also be symptoms of other underlying pathologies. Migraine, CH and HH seems to be related to sleep stages suggesting that they may in fact be a chronobiological disorder. Patients suffering from chronic morning or nocturnal headache should be considered for the presence of possible sleep disturbances.