According to a comprehensive meta-analysis of available studies, migraine and cluster headaches have strong associations with the circadian system – an internal clock which regulates bodily processes – which regulates bodily processes and clocks internal body processes.
Meta-analyses on migraine and cluster headache studies that included circadian features were included in this analysis, including studies that examined when attacks occur throughout the day as well as throughout the year and studies exploring whether genes linked to circadian clock are more commonly found among those suffering from such headaches.
Studies on migraine and cluster headaches as well as hormones linked to the circadian system (melatonin and cortisol) were also carried out.
Data suggest that both migraine and cluster headache conditions are strongly cyclic at multiple levels, particularly cluster headaches. This further highlights the significance of hypothalamus – where primary biological clock is housed – as a factor in migraine and cluster headache conditions.
Cluster headache attacks were found to follow a circadian pattern in 71% of individuals, typically peaking between late night and early morning and more frequent attacks occurring during spring and fall months of each year. Two key circadian genes have been linked with cluster headache, and five of the nine genetic risk factors increased chances of experiencing it; these two genetic risk factors show evidence for circadian patterns as well.
Cluster headache sufferers had lower melatonin and higher cortisol levels compared to individuals without them, as well as lower cortisol levels overall.
Over half of individuals showed a circadian pattern for migraine attacks. While attacks typically peaked throughout the day from late morning until early evening, there was also a low point at night when no attacks took place at all. Migraine has also been linked with 2 core circadian genes; out of 168 known migraine-linked genes 110 had circadian patterns as well.
Individuals suffering from migraine had lower urine melatonin levels than non-migraine sufferers, and during an attack this decreased further.
These findings demonstrate the potential use of circadian therapies for headache disorders, including both therapies based on circadian rhythm and those that alter it.
Study limitations included lack of information on factors that influence circadian cycle rhythm, such as medications, night shift work schedule issues or bipolar disorders.
