The increasing use of smartphones and LED lights prevents synchronisation between menstrual and lunar cycles

This is a fascinating article that addresses the relationship between the menstrual cycle and the lunar cycle. The study was conducted with 176 women, mainly European, who recorded their menstrual cycle for an average of five years and eight months.

Overall, this article is exciting, but it should be read with the necessary precautions when reading any scientific article. The first two results [a statistically significant relationship between the lunar (light) cycle and the menstrual cycle, and that the menstrual cycle is controlled by a circadian clock with a limited training period] are very convincing and consistent with other studies, reinforcing the idea that the lunar cycle and the menstrual cycle have temporal associations and that a biological clock may be involved. The other three results, the hypotheses about the role of lunar gravimetry, light pollution and their confirmation by Google search profiles for “painful menstruation”, present a modest level of evidence. However, they are interesting because they raise questions that should not be dismissed but, on the contrary, can and deserve to be investigated in other studies and by other researchers, with other approaches and larger populations.

As in other living beings, our body is coordinated by a central clock that responds mainly to the light-dark cycle, thus regulating our behaviour. However, in the reproductive sphere, and unlike what is observed in many animal species, there is still controversy about the influence of the moon on the menstrual cycle.

In this new longitudinal study published in the prestigious scientific journal Science Advances, the team led by Dr. Charlotte Helfrich-Förster analyses more than 170 menstrual records of women of different nationalities, collected between 1950 and 2024, to explore their relationship with lunar cycles, established based on the luminescence or gravitational effect of the satellite. The results show a certain synchrony between menstruation and the full moon and new moon phases, especially before 2010. After that date, this association appears to weaken, which the authors relate to increasing exposure to LED light, both from urban centres and electronic screens. On the contrary, the analysis reveals that the influence of gravitational lunar cycles seems to remain, being more pronounced in January due to the proximity of the Earth and the Moon to the Sun.

The publication is based on solid data and methods, thus expanding on previous research on this phenomenon and also supporting the existence of previously unknown regulatory mechanisms of the menstrual cycle, as noted in another interesting article published in the same journal last April. It should be noted that these are correlations, not a proven causal relationship, due to the complexity of the phenomenon, so the finding may not be generalisable to all women. In any case, this research consolidates an interesting field of study that deserves to be explored in the coming years.

From a chronobiology perspective, this research emphasises the importance of environmental factors, such as exposure to artificial light at night, in the regulation of reproductive physiology. Beyond the scientific curiosity aroused by the relationship between the moon and the menstrual cycle, the findings invite reflection on how changes in our modern lifestyle can modulate fundamental biological rhythms. Encouraging habits that respect circadian rhythms, such as adequate sleep hygiene and reduced exposure to night-time light, is essential for promoting overall health.