Circadian rhythms of migraine attacks in episodic and chronic patients: a cross sectional study in a headache center population

Background: Migraine is considered a disease with diurnal and 24 h pattern, though the existence of a prevalent circadian rhythm associated to migraine frequency and severity is still not clear. This observational cross-sectional study aimed to: 1. Assess the circadian rhythm of migraine attacks onset in a large patients' population selected in a headache center and including episodic and chronic migraine 2. Analyze the principal characteristic of the different onset time groups 3. Verify if migraine features, particularly those associated to chronic and disabling migraine, could be discriminant factors for time of onset group.

Methods: We selected 786 consecutive migraine outpatients, who correctly completed the headache diaries for 3 consecutive months and who fulfilled the diagnosis of migraine without aura-MO, migraine with typical aura alone or associated to migraine without aura - MO/MA and chronic migraine - CM. For the time of headache onset, we considered four time slots, from 6 to 12 am (morning), from 1 to 6 pm (afternoon), from 7 to 11 pm (evening), from 12 pm to 5 am (night), and an additional category named "any time". Each time slot included the 60 min preceding the next one (e.g. an onset at 12.30 am was included in 6-12 am time slot). We evaluated in all patients the pericranial tenderness, anxiety and depression tracts, headache-related disability, sleep features, quality of life, allodynia and fatigue.

Results: We scored a total of 16,578 attacks, distributed in the entire day. The most of patients, including CM, satisfied the criteria for the "any time" onset. Night onset was significantly less represented in the MA/MO group. Patients with prevalent night onset were significantly older, with longer migraine history and shorter sleep duration. Age and illness duration were the variables discriminating the different onset time groups.

Conclusions: The most of migraine patients do not report a specific circadian profile of attacks occurrence. Frequent migraine, severe disability, psychopathological tracts as well as central sensitization signs, do not match with a specific circadian rhythm of attacks onset. Night onset migraine seems to be an age related feature, emerging in the course of the disease.