The influences of sleep duration, chronotype, and nightwork on the ovarian cycle

ABSTRACT

Despite research indicating that sleep disorders influence reproductive health, the effects of sleep on reproductive hormone concentrations are poorly characterized. We prospectively followed 259 regularly menstruating women across one to two menstrual cycles (the BioCycle Study, 2005–2007), measuring fasting serum hormone concentrations up to eight times per cycle. Women provided information about daily sleep in diaries and chronotype and night/shift work on a baseline questionnaire. We evaluated percent differences in mean hormone concentrations, the magnitude of shifts in the timing and amplitude of hormone peaks, and the risk for sporadic anovulation associated with self-reported sleep patterns and night/shift work. We estimated chronotype scores – categorizing women below and above the interquartile range (IQR) as “morning” and “evening” chronotypes, respectively. For every hour increase in daily sleep duration, mean estradiol concentrations increased by 3.9% (95% confidence interval [CI] 2.0, 5.9%) and luteal phase progesterone by 9.4% (CI 4.0, 15.2%). Receiving less than 7 hours of sleep per day was associated with slightly earlier rises in peak levels for several hormones. Women reporting night/shift work (n = 77) had lower testosterone relative to women employed without night/shift work (percent difference: −9.9%, CI −18.4, −0.4%). Women with morning chronotypes (n = 47) had earlier rises in estradiol during their cycles and potentially an earlier rise in luteinizing hormone. Compared to those who had intermediate chronotypes, women with evening chronotypes (n = 42) had a later luteinizing hormone peak of borderline statistical significance. A reduced risk for sporadic anovulation was suggested, but imprecise, for increasing hours of daily sleep leading up to ovulation (risk ratio 0.79, CI 0.59, 1.06), while an imprecise increased risk was observed for women with morning chronotypes (risk ratio 2.50, CI 0.93, 6.77). Sleep-related hormonal changes may not greatly alter ovarian function in healthy women, but have the potential to influence gynecologic health.

KEYWORDS:

• Sleep
• menstrual cycle
• hormones
• anovulation
• longitudinal studies

Acknowledgments

We would like to thank the BioCycle Study participants for their time and efforts.

Disclosures of interest

The authors report no conflict of interest.

Data availability

The datasets generated and/or analyzed during the current study are not publicly available, but are available from the corresponding author on reasonable request.

Supplementary material

Supplemental data for this article can be accessed on the publisher’s website.

Additional information

Funding

This work was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health [Contract Numbers: HHSN275200403394C, HHSN275201100002I, and Task 1 HHSN27500001].