Ecochard, R., Stanford, J. B., Fehring, R. J., Schneider, M., Najmabadi, S., & Gronfier, C. (2024). Evidence that the woman's ovarian cycle is driven by an internal circamonthly timing system. Science advances. https://doi.org/10.1126/sciadv.adg9646
Ecochard R, Stanford JB, Fehring RJ, Schneider M, Najmabadi S, Gronfier C. Evidence that the woman's ovarian cycle is driven by an internal circamonthly timing system. Science advances. 2024. doi:10.1126/sciadv.adg9646
Ecochard, René, et al. "Evidence that the woman's ovarian cycle is driven by an internal circamonthly timing system." Science advances, 2024.
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Centre de Recherche en Neurosciences de Lyon (CRNL), Neurocampus, Université de Lyon, Lyon, France. Electronic address: claude.gronfier@inserm.fr.029brtt94
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RRM Academy Synopsis
Cycle length data give evidence of an internal monthly timer
Researchers studied existing cycle records from women with no known cycle disorders: a European group of 2303 women (26,912 cycles) and a North American group of 721 women (4786 cycles). Cycle length fit a pattern from an internal, clock-like timer better than any other process tested. Period start dates also lined up weakly, but significantly, with the 29.5-day moon cycle.
Key Findings
Among 425 European women with series of 18 cycles or more, 1846 oscillations of four cycles or more appeared, a mean of 4.3 oscillations per woman.
Of the 1846 oscillations, 890 (48%) occurred in a stable state and 906 (49%) followed an abrupt cycle lengthening, called a phase jump.
In the European data, second, third and fourth order partial autocorrelations of cycle length were significant (P = 0.0032, P < 0.0001 and P = 0.001).
In the North American data, cycle lengths were linked only at the third order: autocorrelation P = 0.0084 and partial autocorrelation P = 0.0030.
European periods began most often in the waxing crescent: 3533/26,912 (13.1%) against 12.5% expected from an equal spread across eight lunar phases.
Interpretation
This analysis reviewed archived daily cycle records from two groups of women with no known cycle disorders. Patterns in the autocorrelations and repeated phase jumps point to an internal, clock-like timer that governs cycle length. Period start dates also tracked the lunar cycle more often than chance would predict. The authors note they could not separate the timer's effect from the moon's effect in this analysis. The findings support larger studies that test and confirm this internal timer directly.
RRM Context
Restorative reproductive medicine treats the ovulatory cycle as a vital sign worth tracking. Cycle records kept by women using fertility awareness methods made this analysis possible. Two of the datasets came from the Billings and Marquette methods. The authors call for larger studies, and for tests of timing based care, once the timer is confirmed.
Our editorial summary of this paper, not the article's abstract.
Abstract
The ovarian cycle has a well-established circa-monthly rhythm, but the mechanisms involved in its regularity are unknown. Is the rhythmicity driven by an endogenous clock-like timer or by other internal or external processes? Here, using two large epidemiological datasets (26,912 cycles from 2303 European women and 4786 cycles from 721 North American women), analyzed with time series and circular statistics, we find evidence that the rhythmic characteristics of the menstrual cycle are more likely to be explained by an endogenous clock-like driving mechanism than by any other internal or external process. We also show that the menstrual cycle is weakly but significantly influenced by the 29.5-day lunar cycle and that the phase alignment between the two cycles differs between the European and the North American populations. Given the need to find efficient treatments of subfertility in women, our results should be confirmed in larger populations, and chronobiological approaches to optimize the ovulatory cycle should be evaluated.
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