Reacción a "Reactions: menstrual cycle depends on an internal 'clock'"

The study by Ecochard et al. published in Science Advances shows a high methodological quality, as it includes a large number of data points (more than 3,000 women collectively, providing data from more than 30,000 menstrual cycles). In addition, the authors apply specific statistical techniques for the analysis of chronobiological patterns.  

However, the study is limited to participants living in Europe and North America and most of the data was collected before 2000. Firstly, it would be appropriate to conduct the analysis with participants from, if not all continents, at least both hemispheres and different latitudes. These geographical differences, as well as the different seasons, could provide interesting information on other external mechanisms that could be interfering with the process, beyond the lunar phases. In addition, as the authors point out, light pollution has increased in recent decades with greater night-time illumination and increased use of screens and backlit devices. Therefore, it would be interesting to also collect data on participants' light exposure, among other lifestyle variables. 

During routine ovarian stimulation treatments, substances are administered to pharmacologically control the functioning of the ovaries, independently of the internal control of the process, so this would have a no direct impact on clinical practice. However, if a mediator (e.g. melatonin or light therapy) were to be discovered that could play a role in regulating ovarian function, this could be useful to improve ovarian response, for example in treatments with low doses of hormones. 

However, this is an emerging field and much work remains to be done to confirm the results and describe the molecular mechanisms involved. Once this knowledge has been obtained, it will be time to test the effectiveness of different strategies to exploit the control of the menstrual cycle rhythm to improve the results of fertility treatments.