Shift work, especially rotating shift work, was found to significantly affect the timing of natural menopause, according to the results of a study published in Menopause.
Researchers prospectively investigated the association between shift work exposure and variations in age at natural menopause in adult workers by analyzing data from the Canadian Longitudinal Study on Aging.
A total of 3688 premenopausal women who participated in 3 years of follow-up were included, and self-reported information regarding their menopausal and work status was evaluated. Information obtained on exposure to shift work included ever being exposed to shift work, exposed to shift work in current job, and exposed to shift work in longest job. Age in years was used as a time scale for survival analysis, and age at natural menopause was the primary outcome.
The mean age of participants at their baseline interview was 48.9 years (SD 0.08), and a majority of participants were White (94.3%).
Among the cohort, 20% of women reported that they were ever exposed to shift work during their jobs, with 3.6% and 8.1% of currently working women reporting that they were exposed to night and rotating shift work, respectively.
Compared with women who worked during the day, those who were ever exposed to any type of shift work were more likely to have a later age at natural menopause (hazard ratio [HR] 0.77; 95% CI, 0.61-0.98). Regarding currently working women, night shift workers were at increased risk for earlier menopause (HR 1.27; 95% CI, 0.72-2.24), and rotating shift workers were more likely to have a later age at menopause compared with daytime workers (HR 0.64; 95% CI, 0.46-0.89).
Women who worked the night shift at their longest job were at increased risk for early menopause (HR 1.32; 95% CI, 0.92-1.91), and those who reported working in rotating shifts at their longest job had a later age at menopause compared with daytime workers (HR 0.65; 95% CI, 0.49-0.86).
The overall risk for early menopause was found to be significantly increased in women who were current smokers (HR 1.49; 95% CI, 1.09-2.03) and who participated in regular physical activity (HR 1.21; 95% CI, 1.03-1.40). Workers who were overweight (HR 0.76; 95% CI, 0.63-0.91), obese (HR 0.77; 95% CI, 0.62-0.95), and with high parity (HR 0.83; 95% CI, 0.70-0.97) were found to be at significantly increased risk for later menopause.
Limitations of the study include pooling by the researchers of evening and night shift data, and they were unable to obtain some information related to shift work, such as the type and direction of rotating shifts, number of consecutive night shifts worked, and the number of days off between shifts. Also, they were unable to obtain the exact timing of exposure, age at menarche, or information regarding breastfeeding. Furthermore, most of the data were derived from questionnaires based on memory recall, and most study participants were White.
“Although our findings do not offer conclusive evidence, they do suggest that a delaying effect of rotating shift work exposure on [age at natural menopause] might be plausible,” stated the study authors. “Detailed information related to shift work on scheduling, workplace, and personal factors is desirable for higher quality research related to shift work and reproductive health outcomes.”
Khan D, Rotondi M, Edgell H, Tamim H. 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). Menopause. Published online March 25, 2022. doi:10.1097/GME.0000000000001981