The introduction of monoclonal antibodies (mAbs) directed against the calcitonin gene-related peptide (CGRP), or its receptor (CGRPr), revolutionized migraine management due to their high efficacy and few side effects. Data suggest that the CGRP may even be implicated in circadian rhythm, but studies about the effect of anti-CGRP treatments on sleep are still lacking. The aim of the present study was to assess the effect of erenumab (70 and 140 mg per month), a human mAb directed against CGRPr, on chronotype in chronic migraineurs; secondly, we assessed its efficacy, safety, and the effects on anxiety and depression. Sleep was evaluated using self-administrable questionnaires investigating chronotype, sleep quality, and daytime sleepiness. Migraine diaries and several self-administrable questionnaires regarding headache impact and psychological correlates were evaluated every 3 months during 12 months of treatment. Eighty-eight patients were included; most of them showed a significant reduction in headache frequency and an improvement in psychological symptoms. Moreover, an initial change in chronotype was observed at the three-month assessment from a morning chronotype to an intermediate one; a similar trend remained in the other evaluations, even if it did not reach a statistical significance. Lastly, patients who responded to the treatment showed a progressive sleep efficiency reduction. The present real-life study hypothesized the influence of erenumab on chronotype, representing a link between circadian rhythm, CGRP, and migraine.

The cluster headache is a primary headache characterized by attacks of unilateral pain associated with ipsilateral cranial autonomic features. These attacks recur in clusters during the years alternating with periods of complete remission, and their onset is often during the night. This annual and nocturnal periodicity hides a strong and mysterious link among CH, sleep, chronobiology and circadian rhythm. Behind this relationship, there may be the influence of genetic components or of anatomical structures such as the hypothalamus, which are both involved in regulating the biological clock and contributing even to the periodicity of cluster headaches. The bidirectional relationship manifests itself also with the presence of sleep disturbances in patients affected by cluster headaches. What if the key to studying the physiopathology of such disease could rely on the mechanisms of chronobiology? The purpose of this review is to analyze this link in order to interpret the pathophysiology of cluster headaches and the possible therapeutic implications.