Working shifts may delay the onset of menopause

It is no secret that working nontraditional shifts can wreak havoc on lifestyle and sleep habits. Shift work has also been known to have a negative effect on workers’ health. A new study suggests it also may delay the onset of natural menopause, possibly because of disruptions in circadian rhythms.

Shift work has increased globally in recent years, with an estimated 20% of the economically active population in North America and Europe working some type of nontraditional or alternating shifts. Although shift work has become an economic necessity to keep up with the increased demand for goods and services, it is not without health risks. Previous studies have linked shift work with an increased risk of coronary events, with the highest risk being associated with night shifts. Other related health problems include peptic ulcers, type 2 diabetes, and cancers such as prostate, colorectal, and breast.

Although previous studies have shown the various adverse health effects of shift work on working adults, there has been little research on the effect of shift work on middle-aged and older adults. Age at natural menopause is a matter of concern for middle-aged and older women, because both early or late menopause may be a significant risk marker for subsequent morbidity and mortality. Environmental factors such as smoking, parity, and socioeconomic status have previously been identified to be strongly associated with variations in age at natural menopause.

Researchers have hypothesized that a factor that may affect age at menopause is shift work, as previous studies have suggested a possible effect of circadian rhythm disruption on ovulation and fertility. In addition, excessive exposure to artificial light during dark hours has been documented to cause melatonin suppression that, in turn, leads to disruption of ovarian activity. To date, little has been documented regarding the relationship between shift work and age at natural menopause.

This study, based on secondary data analyses of nearly 3,700 premenopausal women, aimed to investigate the association between shift work exposure and variations in age at natural menopause in adult Canadian workers. Based on study results, a significant relationship has been shown between rotating shifts and delayed onset of menopause. The researchers speculate that disruptive circadian rhythms may play a role, although further investigation is necessary.

Abstract

Objective: A wide range of negative health outcomes have been associated with shift work (SW) particularly night and rotating SW. However, little is known about effects of SW exposure on reproductive health outcomes. The objective of our study is to prospectively investigate the association between SW exposure and the variations in age at natural menopause among adult Canadian workers.

Methods: Secondary data analyses were performed using the Canadian Longitudinal Study on Aging database. Premenopausal women (N = 3,688) at baseline were followed prospectively for 3 years. Three derived variables were used to measure SW primary exposure: 1) ever exposed to SW, 2) SW exposure in current job, and 3) SW exposure in the longest job. Cox proportional hazard regression models were used to evaluate risk of variations in age at natural menopause after adjusting for potential confounders.

Result: One out of five women (20%) reported to be ever exposed to SW during their jobs. Overall, women who were ever exposed to SW were significantly associated with a delayed onset of menopause compared with daytime workers (hazard ratios [HR] = 0.77, 95% CI, 0.61-0.98). Particularly, when compared with daytime workers, rotating shift worker in the current and longest job were significantly related to delayed onset of menopause (HR = 0.64, 95% CI, 0.46-0.89 and HR = 0.65, 95% CI, 0.49-0.86), respectively.

Conclusion: Our results suggest a relationship between rotating shift and delayed onset of menopause. We speculate that disruptive circadian stimuli may play a role in menopausal onset and this warrants further investigation.

Content created 23 March 2022

Reference

Durdana Khan, Michael Rotondi, Heather Edgell, Hala Tamim. 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)  2022 Mar 25. doi: 10.1097/GME.0000000000001981. Online ahead of print.