Evidence that the woman's ovarian cycle is driven by an internal circamonthly timing system

René Ecochard; Joseph B Stanford; Richard J Fehring; Marie Schneider; Shahpar Najmabadi; Claude Gronfier

doi:10.1126/sciadv.adg9646

Menstrual Cycle · Cycle Physiology

Evidence that the woman's ovarian cycle is driven by an internal circamonthly timing system

Ecochard R, Stanford JB, Fehring RJ, Schneider M, Najmabadi S, Gronfier C

Published April 12, 2024 Science advances

DOI 10.1126/sciadv.adg9646 PMID 38598621 PMC PMC11006216

RRM Academy Synopsis

Cycle length data give evidence of an internal monthly timer

Researchers re-analyzed existing cycle records from women with no known cycle disorders. The records covered 2303 European women (26,912 cycles) and 721 North American women (4786 cycles). Cycle lengths were more likely explained by an internal clock-like timer than other processes. The 29.5-day lunar cycle showed a weak but significant link to period start dates.

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 is a statistical analysis of existing cycle records. Such an analysis describes patterns and cannot show what drives them. The authors call their findings clues for an internal timer and say more work must test the idea. The women had no known cycle disorders and most were under 35 years old. Women with cycle disorders were outside the study. The lunar link was weak, and its phase alignment differed between the European and North American groups. The authors could not measure the timer's effect and the moon's effect separately.

RRM Context

Restorative reproductive medicine treats the ovulatory cycle as a sign of health worth understanding. Cycle records made this analysis possible. Two datasets carry the names Billings and Marquette. The authors propose clinical trials of timing-based approaches to the ovulatory cycle, if 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.

Topics

Menstrual Cycle › Cycle Physiology › Cycle Variability · Reproductive Endocrinology › Ovulation Physiology › Follicular Development

René Ecochard, Joseph B Stanford, Richard J Fehring, Marie Schneider, Shahpar Najmabadi, Claude Gronfier

R Ecochard, Joe Stanford, Joey Stanford, J Stanford, Rick Fehring, Dick Fehring, Rich Fehring, R Fehring, M Schneider, S Najmabadi, C Gronfier

PMID 38598621 38598621 DOI 10.1126/sciadv.adg9646 10.1126/sciadv.adg9646 Ecochard et al. 2024, Ecochard 2024

Evidence that the woman's ovarian cycle is driven by an internal circamonthly timing system

Cycle length data give evidence of an internal monthly timer

Key Findings

Interpretation

RRM Context

Abstract

Topics

By this author

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