Figure 4.

The relationship between subjective sleep quality and the combination of lunar phase (light, dark, neutral periods) in the two most recent menstruation onsets. Participants were categorized by the combination of lunar phases at the most recent and the second most recent onset of menstrual cycle (A,B), and the proportions of good and poor sleepers were calculated (C). The proportion of good sleepers was highest in the “both light period” group, followed by the “light and neutral period” group and the “both neutral period” group. The “both dark period” group and the “other (light and dark period)” group showed the lowest proportions of good sleepers.