CIRCADIAN rhythm refers to the natural internal clock that regulates body processes, including the sleep-wake cycle. A meta-analysis performed by researchers from the University of Texas Health Science Center, Houston, USA, revealed that migraines and cluster headaches are both strongly associated with circadian rhythm.
Researchers examined information on the timing of headaches throughout the day and during the year, as well as studies on cluster headaches, migraines, and hormones related to the circadian system, such as cortisol and melatonin. They also investigated whether genes associated with the circadian cycle were more prevalent in individuals with these headaches.
The data suggested that both headache disorders, especially cluster headaches, are highly circadian at multiple levels. A circadian pattern of headache episodes was observed in 71% of individuals, where episodes peaked in the late hours of the night to early hours of the morning. Throughout the year, individuals had more episodes in spring and autumn. On a genetic level, cluster headaches were linked with two significant circadian genes, and five out of the nine genes which increased the likelihood of having cluster headaches were genes with a circadian pattern of expression. Compared to individuals without cluster headaches, higher cortisol levels and lower melatonin levels were observed in individuals with cluster headaches.
The meta-analysis revealed a circadian pattern in 50% of individuals with migraine episodes. A circadian low point was observed during the night, where few episodes occurred. Migraines were also associated with two core circadian genes, and 110 out of the 168 genes associated with migraines were genes with a circadian pattern of expression. Interestingly, individuals with migraines had lower levels of melatonin in their urine compared to individuals without migraines. Additionally, melatonin levels were lower during a migraine episode.
The results reaffirm the important role that the hypothalamus, an area of the brain which encloses the primary biological clock, plays in cluster headaches and migraines. Notably, the findings raised the potential for using circadian-based therapies to treat headache disorders, including both treatments based on the circadian rhythm; for example, by taking medications at a certain time of the day, and using treatments that cause circadian changes.
