Rotating shift workers are likely to have delayed menopause, suggests a study published in the journal Menopause.

Researchers included 3688 premenopausal Canadian women, aged 45-85 years, from the Canadian Longitudinal Study on Aging (CLSA) database for their study to determine the link between shift work and age at natural menopause over a period of three years. Twenty percent of women affirmed shift work in their present or previous jobs. Of these, 3.6% worked night shifts, while 8% were engaged in rotating shift work.

Natural menopause was significantly delayed in women who had worked nights or in rotating shifts at some point of time compared to those who were currently working during daytime; 54 vs 55 years with a hazard ratio of 0.77. When currently employed women were analysed, night shift workers attained natural menopause at an earlier age of 53 years (average); women who were working rotating shifts reached menopause later at 55 years (average) with hazard ratio of 0.64.

Overweight (HR 0.76), obese (HR 0.77) and multiparous (HR 0.83) women were likely to have late natural menopause, while women who were physical active (HR 1.21) and were current smokers (HR 1.49) attained menopause at an earlier age.

This study documents the impact of shift work on menopausal age. Disturbed circadian rhythm and its effect on estrogen levels have been suggested to play a role in this, although exact mechanisms are not well understood. According to the authors, rotating shift work possibly causes greater disruption of the circadian rhythm than regular night shift work, thus delaying menopause.

Reference

1. The association between shift work exposure and the variations in age at natural menopause among adult Canadian workers: results from the Canadian Longitudinal Study on Aging (CLSA). http://www.menopause.org/docs/default-source/press-release/shift-work-and-age-at-menopause.pdf.