Lowered circannual urinary melatonin concentrations in episodic cluster headache.

The circannual secretion of melatonin in 14 Swedish and 15 Italian patients suffering from episodic cluster headache was compared with 14 Swedish and 15 Italian healthy controls matched for sex and age. Overnight samples of urine were collected once a month from 8 to 14 months and kept at -20 degrees C until analysed with RIA. The melatonin concentrations in nocturnal urine were permanently low in cluster headache and there was no consistent change of the melatonin concentration in relation to cluster periods occurring during the study. There was no definitive circannual or infraannual rhythmicity of melatonin in patients or controls. Multiple analysis of variance with repeated measurements showed a significant effect of disease (p < 0.05), but not of time. Sex, geographical location, age, and smoking also had significant effects (p < 0.001) on the melatonin concentrations. Lower melatonin levels in cluster headache patients than in controls may in part be related to a larger number of smokers in the patient group. The relation between tobacco use and melatonin should be further studied.