The influence of phototherapy on circadian melatonin and sleep regulation and potential benefits of these pathways in the management of vitiligo: a narrative review

Ultraviolet B narrow band (UVB-NB) phototherapy is the gold standard treatment for vitiligo, primarily due to its immunomodulatory effects. Additionally, it may influence circadian melatonin balance, that may indirectly induce sleep regulation, which in turn could potentially contribute to vitiligo improvement. The association between melatonin, vitiligo and phototherapy has been little investigated. The aim of this study was to evaluate the current evidence regarding the effects of circadian melatonin regulation and sleep, particularly during vitiligo treatment with phototherapy. We undertook a narrative review to synthetize the evidence on this association through the MEDLINE/PubMed database, using combined search terms: melatonin, vitiligo, phototherapy, and circadian rhythm (sleep). A total of 56 articles were included. There are few studies on this relationship, and conflicting findings. Some studies have suggested that UV exposure and phototherapy might benefit vitiligo by stimulating melanocytes, which have melatonin receptors, and this could potentially synchronize the circadian regulation of melatonin. This improved melatonin balance could result in better sleep quality further enhancing the antiinflammatory properties of melatonin and contributing to vitiligo improvement. Less is known about the possible effects of the use of topical melatonin, with or without phototherapy, to treat vitiligo lesions. In conclusion, there is some evidence that circadian melatonin regulation plays an important role in the course of vitiligo, both through sleep regulation and its anti-inflammatory properties. The evidence suggests that the systemic and physiological properties of melatonin, especially its circadian behavior regulated by phototherapy, may be more effective in respect of vitiligo improvement than the use of topical melatonin. However, the effects of the oral intake of melatonin are less clear. Phototherapy, as a potential modulator of circadian melatonin rhythm, that influences sleep and clinical improvement of vitiligo, needs further examination, as does the use of melatonin as an adjuvant treatment to UVB phototherapy in vitiligo.