2024-04-12 12:12:11
An international research team compared a large number of menstrual cycle data collected in European and North American studies. this study shows that the menstrual cycle is finely regulated by an internal clock, itself occasionally influenced by the lunar cycle.
Due to their cyclical rhythm and similar durations, a link between menstrual cycle and lunar cycle has often been assumed, without science having until now managed to provide solid proof. In order to better understand the origin of the rhythmic regularity of the menstrual cycle, an international research team bringing together Inserm, the CNRS and the Claude Bernard Lyon 1 University, compared a large number of cycle data, collected in studies European and North American. Its results show that the menstrual cycle is finely regulated by an internal clock, itself occasionally influenced by the lunar cycle. This work will appear in Science Advances argue for the interest of further studying this potential link on larger datasets, in order to identify a possible interest of chronobiology in the treatment of fertility disorders.
A typical ovulatory cycle, or menstrual cycle, in humans lasts on average 29.3 days, with variations in duration from one menstruating person to another and from one cycle to another in the same person. It begins on the first day of menstruation and is made up of three phases, each dedicated to carrying out a specific process linked to ovulation which occurs around the 14th day of the cycle.
Some work has suggested that each of these three phases could take place under the influence of an internal clock whose disruption of the rhythm would be associated with irregularities in the menstrual cycle.
In humans, the best-known internal clock is the circadian clock, very close to 24 hours, which maintains the sleep-wake cycle and all physiological rhythms. It is in phase with the day-night cycle under the influence of light. When the circadian clock is disrupted – as in the case of jet lag for example – it takes a few days to reset to its usual rhythm by resynchronizing with the new day-night cycle.
In the case of menstrual cycles, the involvement of an internal clock could manifest itself in a similar way: the duration of the cycle would usually be highly stable in the same person and, in the event of a disturbance, adaptation mechanisms by synchronization with External conditions would come into play to restore the optimal rhythm.
So what could this “external synchronizer” be? A recurring theory suggests that the lunar cycle could play this role, but scientific evidence is lacking to date.
An international research team led by Claude Gronfier, Inserm researcher at the Lyon Neurosciences Research Center (Inserm/CNRS/Université Claude Bernard Lyon 1), was interested in the potential existence of an internal biological clock which would regulate the menstrual cycle and which could be synchronized with the lunar cycle. Thanks to a large database of menstrual cycles collected as part of European and North American studies, she was able to compare a total of nearly 27,000 menstrual cycles in 2,303 European women and nearly 4,800 cycles in 721 North American women. .
Firstly, the researchers examined the stability from one menstrual cycle to another at the individual level, by comparing the duration of successive cycles. They thus observed an overall stability in the average duration of each participant’s cycle, even though over a set of successive cycles, some actually lasted longer or shorter than her “standard” cycle.
“These observations suggest the existence of a mechanism which would correct the difference between the duration of the current cycle and that of a typical menstrual cycle in the person concerned,” explains René Écochard, first author of the study, doctor at Hospices Civils. of Lyon and professor at Claude Bernard Lyon 1 University. “A few shorter cycles could thus compensate for a series of a few longer cycles so that the total length of the cycle oscillates around the usual length of the menstrual cycle. The duration of a cycle could therefore depend on the duration of previous cycles.”
“The observation of this phenomenon argues in favor of the existence of an internal clock finely regulating menstrual cycles, itself synchronized by an environmental cyclical event”, adds Claude Gronfier.
Secondly, the research team was interested in the potential relationships between the occurrence of menstruation in the cycles studied and the phases of the moon at the time of data collection.
She was thus able to observe an association, occasional but significant, between the menstrual cycle and the lunar cycle, with however – and without this work making it possible to rule on the cause – a major difference between the European cohorts and the northern cohort. American : among Europeans, the cycle most often began during the waxing phase of the moon while it began more often at the full moon in the North American cohort.
“Despite this astonishing difference that we are unable to explain at the moment, the links identified in this work between the lunar and menstrual cycles, due to their proximity to certain phenomena that we observe in chronobiology, suggest that the periodicity of menstruation and ovulation could be influenced, in a modest but significant way, by the lunar cycle”, specifies Claude Gronfier.
These results therefore argue in favor of an internal clock system with a quasi-monthly rhythm, weakly synchronized by the lunar cycle. However, they require further investigation and confirmation by laboratory studies and larger epidemiological studies. “Thanks to cycle recording applications for smartphones, the emergence of large databases containing the cycle information of several hundred thousand women could provide new study opportunities”indicates René Écochard.
“Confirming the existence of an internal clock coordinating the menstrual cycle, as well as the mechanisms involved in its synchronization, could make it possible to apply so-called “circadian”, personalized medicine approaches – already used in oncology and for the treatment of disorders. from sleep or depression, for example – to issues such as ovulation and fertility disorders,” concludes Claude Gronfier.
Inserm, Regularity of the menstrual cycle: a biological clock modulated by the moon?, April 10, 2024.
1713070661
#Regularity #menstrual #cycle #biological #clock #modulated #moon