A report published in 1806 by the French physician J. The question of whether lunar changes might somehow entrain the menstrual rhythm has been discussed for many years. It has been hypothesized that there are lunar effects on human biology including psychosis, violent behavior, birth, and menstruation, although most of these proposed influences of the moon on human physiology have not been able to be statistically confirmed. The effects of the lunar phase on the human reproductive rhythm have not yet been elucidated, although mature women have a 29.5-day menstrual cycle. Moonlight has been revealed to control the regular oscillation of clock gene expression in fish, suggesting that the light/dark periods of the lunar cycle affect the daily expression of clock genes and influence the sleep and/or diurnal rhythms of biochemical reactions. Furthermore, other animals are clearly influenced by the moon and possess internal clocks that can predict the lunar cycle. Published data suggest that organisms such as palolo worms, which are polychaete worms living on coral islands, have an endogenous circalunar clock. The reproductive cycles of marine organisms are linked to changing levels of moonlight and the tidal cycle, both of which are governed by the phases of the moon. Adaptations of animals to the lunar cycle (approximately 29.5 days) are frequently observed. Organisms have evolved to live with geophysical cycles of different period lengths.

Menstrual cycle onset in the dark period was associated with a deterioration in subsequent subjective sleep quality, which was more apparent with consecutive onsets in the dark period or at a rapidly changing lunar phase. When participants were categorized by the combination of lunar phases (light, dark, neutral periods) in the two most recent menstrual cycle onsets, the “both dark period” group and the “other (light and dark) period” group showed the lowest proportion of good sleepers. Interestingly, the proportion of good sleepers with menstrual cycle beginning during the light period was significantly higher than that during the dark period, while the proportion of poor sleepers with menstrual cycle beginning during the dark period was significantly higher than that during the light period. Overall, there was no association between the onset of menstrual cycle and lunar phase. We also collected questionnaire survey data on sleep quality from each participant. Menstrual cycle onset data from the six most recent menstrual cycles were obtained for 529 women (aged 25–39 years) using the smartphone app Luna Luna.

The aim of the present study was to investigate the association among lunar cycle, menstrual cycle onset, and subjective sleep quality.

Lunar cycle 2021