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Abstract
Introduction. The study determined the effect of seasons and meteorological variables on ovarian-menstrual function.
Methods. Women (N = 129) living in Novosibirsk (55°N), Russia, provided data on normal menstrual cycles for over 1 year between 1999 and 2008. Of these, 18 together with 20 other healthy women were investigated once in winter and once in summer in 2006–2009. The investigated variables included serum levels of follicle-stimulating hormone (FSH), luteinising hormone (LH) and prolactin on day ∼7 of the menstrual cycle, ovary follicle size (by ultrasound) on day ∼12 and ovulation occurrence on subsequent days.
Results. In summer vs. winter, there was a trend towards increased FSH secretion, significantly larger ovarian follicle size, higher frequency of ovulation (97% vs. 71%) and a shorter menstrual cycle (by 0.9 days). LH and prolactin levels did not change. In all seasons combined, increased sunshine (data derived from local meteorological records) 2–3 days before the presumed ovulation day (calculated from the mean menstrual cycle) led to a shorter cycle length. Air/perceived temperature, atmospheric pressure, moon phase/light were not significant predictors.
Conclusions. Ovarian activity is greater in summer vs. winter in women living in a continental climate at temperate latitudes; sunshine is a factor that influences menstrual cycle.
Acknowledgements
The study was sponsored by Lumie® (Cambridge, England); the work of the research team was supported by VELUX Foundation (Switzerland; project # 482, 2007-2009); OYS was paid by grant EUCLOCK (the EU 6th Framework project # 018741, 2006–2011). The authors thank study participants for their involvement, O.V. Chechel and A.I. Mikhalyuk for blood sampling, Drs. E.O. Styopkina and M.V. Ivanova for hormonal assays, Dr. R. Ecochard for providing data for this study, P. Bröde for providing information on BioKlima tool, A. Wirz-Justice for comments on the manuscript, E. Price of Lumie® for English editing.