Even occasional night shift workers are nine per cent more likely to have an early menopause, a study has found.
This matters because women who go through the menopause younger are at greater risk of cardiovascular disease, osteoporosis and may even suffer memory problems.
Researchers tracked more than 80,000 nurses who worked night shifts over 22 years. The risk of early menopause was found in those who worked almost two years of night shifts.
Women who disrupt their body clocks by staying up at night have lower levels of the sleep-hormone melatonin, which some experts believe is important for the ovaries.
But it may also be the stress and tiredness of night-working which disrupt oestrogen levels and plunge women into menopause at an early age.
Dr David Stock, who led the study from the University of Dalhousie in Canada, said, “This is the first study into a link between rotating night shifts and age at menopause, and we found a moderate but significant link.”
Dr Stock added, “For women who went through the menopause before the age of 45, shift work seemed to be particularly important. This could be due to disruption of their circadian rhythms, stress or fatigue, although more research is needed.”
Women who work night shifts have a greater risk of breast and endometrial cancer, previous studies have found.
Working at night, even every so often, is believed to affect sex hormone levels, which can lead to cancer or increase the chances that a woman stops ovulating.
The study looked at nurses who had worked at least three nights in a month, in addition to day and evening shifts.
It found women who had done this for 20 months or more in the preceding two years had a nine per cent greater risk of early menopause.
For those who started the menopause below the age of 45, this many night shifts increased the risk of early menopause by 25 per cent.
If they had done rotating night shifts for more than 20 years, the risk rose to 73 per cent. However, the researchers caution this was seen in only a small group of women.
The study, published in the journal Human Reproduction, concludes, ‘Women already prone to earlier menopause may further truncate their reproductive lifetime by working schedules comprising day as well as night shifts.’
Night shifts, previously suggested to increase women’s risk of miscarriage and premature birth, are concerning because they expose people to artificial light when they are supposed to be asleep.
This is what reduces levels of the sleep-hormone melatonin, which some experts say is vital for keeping ovaries working and producing eggs so women remain able to have children.
Previous evidence suggests that working ‘high-strain’ jobs and those with ‘difficult schedules’ is linked to earlier menopause.
The authors conclude, “Given evidence that nurses are commonly called upon to work long shifts, it is plausible that a substantial proportion of participants may have met these criteria.”
Source: Daily Mail
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