Purpose of review
To delineate the current state of evidence on the impact of night shift work
on age at natural menopause.
The only direct evidence is from a single observational study, which indicates that women who work night shifts are at moderately higher risk for earlier menopause and that this risk is more pronounced among younger women. Underlying biological mechanisms have yet to be sufficiently substantiated. A long-held line of inquiry, most strongly propagated by the observed link between night shift work
and female breast cancer, is the ‘Light at Night’ hypothesis, which suggests melatonin-mediated circadian disruption
as a potential regulator of reproductive signaling in women. Supporting evidence is found from observations of changes in endogenous melatonin production among night working women or in response to light exposure, and corresponding changes in endogenous ovarian hormone levels and modulated menstrual patterns, among other indications of altered central ovulation
-governing processes. Susceptibility to night shift work
may be modified by chronotype
This review summarizes the literature related to night work and ovulatory regulation in humans, prioritizing population-based evidence to provide motivation for the study of circadian disruption
and night shift work
as a regulator of menopausal timing.