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Research has shown that the ovarian cycle is regulated by a circadian rhythm
Last reviewed: 02.07.2025
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Researchers from France and the United States working in the field of reproductive medicine have found that women's monthly cycles are most likely linked to the circadian rhythm. In an article published in the journal Science Advances, the scientists analyzed data on thousands of ovulatory cycles registered by women from Europe and the United States.
The question of what regulates the ovulatory cycle has long been the subject of scientific debate. One of the most common hypotheses was the idea of a connection with the lunar cycle. Charles Darwin suggested that this connection arose when people lived near the sea coast and their daily lives were closely tied to the ebb and flow of the tides. Three years ago, a team of scientists led by chronobiologist Charlotte Förster from Würzburg found that women's menstrual cycles can temporarily synchronize with the phases of the moon. However, in the new study, the team found little evidence of a lunar influence and suggested that the circadian rhythm most likely controls ovulatory cycles.
The circadian rhythm is a 24-hour cycle of physical, mental, and behavioral changes that is common to all living things, including humans. For example, the circadian rhythm regulates sleep, making people sleepy at certain times of the day. It is also known that the circadian rhythm can be altered by the lunar cycle, with people going to bed later and sleeping less on the nights before a full moon.
To study the mechanism that controls ovulatory cycles, the researchers collected medical data from more than 3,000 women in Europe and North America, covering 27,000 ovulatory cycles. They tracked the first day of each cycle and found no significant correlation between the onset of the cycle and the phases of the moon.
But the scientists found another pattern: multiple instances in which something disrupted a woman’s normal cycle, and her body adapted by changing its rhythm over several months to restore a normal cycle. They compared this phenomenon to how the circadian rhythm adapts to jet lag. These observations suggested that the circadian rhythm plays a more important role in regulating ovulatory cycles than the lunar cycle.
Thus, the study results suggest that circadian rhythm, rather than lunar phases, is the main factor influencing ovulatory cycles in women.