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Updated: Jun 8, 2026
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Published on: August 30, 2021
Menstrual cycles are influenced by sunshine.
Konstantin V Danilenko1, Oksana Y Sergeeva, Evgeniy G Verevkin
1Institute of Internal Medicine, Siberian Branch of the Russian Academy of Medical Sciences, Novosibirsk, Russia. kvdani@mail.ru
Summary
Seasonal changes significantly impact ovarian function in women. Increased sunshine in summer correlates with higher ovulation rates and shorter menstrual cycles, indicating environmental influences on reproductive health.
Area of Science:
- Reproductive Endocrinology
- Chronobiology
- Human Physiology
Background:
- Investigates the influence of seasonal variations and meteorological factors on the female reproductive system.
- Examines ovarian-menstrual function in women residing in a temperate continental climate.
Purpose of the Study:
- To determine the effect of seasons and meteorological variables on ovarian-menstrual function.
- To assess seasonal differences in reproductive hormone levels, ovarian follicle size, and ovulation frequency.
Main Methods:
- Longitudinal study of 129 women in Novosibirsk, Russia, over a decade (1999-2008).
- Cross-sectional analysis of 38 women in winter and summer (2006-2009).
- Measured serum FSH, LH, prolactin, ovarian follicle size via ultrasound, and ovulation occurrence; correlated with meteorological data.
Main Results:
- Summer was associated with increased FSH, larger follicle size, higher ovulation rates (97% vs. 71%), and shorter cycles compared to winter.
- Increased sunshine duration 2-3 days prior to ovulation correlated with shorter menstrual cycle length.
- LH, prolactin levels, temperature, and atmospheric pressure were not significant predictors.
Conclusions:
- Ovarian activity is enhanced during summer in women at temperate latitudes.
- Sunshine is identified as a key environmental factor influencing menstrual cycle length and regularity.
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