A study has revealed that women who work night shifts are nine per cent more likely to have an early menopause.
According to Eche Ugochukwu, a general medical practitioner, menopause is the time that marks the end of a woman’s menstrual cycle and that it is diagnosed after a woman has gone 12 months without a menstrual period.
Ugochukwu, said the average age of menopause in Nigerian women is typically between 45 – 54 years, adding however that “menopause may occur as early as the 30s or as late as the 60s.”
The finding of the study is important because research has shown that early menopause raises the risk of heart disease and osteoporosis. Medical experts say women who go through menopause younger are at greater risk of cardiovascular disease, osteoporosis, and may even suffer memory problems.
The researchers tracked more than 80,000 nurses who worked night shifts over 22 years and 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,” reports MailOnline. 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.
According to David Stock, who led the study from the University of Dalhousie in Canada, the study is the first to show a link between rotating night shifts and age at menopause. He added that the researchers found a moderate but significant link.
He said: “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.”
Previous studies have found that women who work night shifts have a greater risk of breast and endometrial cancer. It is also often believed to affect sex hormone levels, which can lead to cancer or increase the chances that a woman stops ovulating.
The study, published in the journal Human Reproduction, 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.
“Women already prone to earlier menopause may further truncate their reproductive lifetime by working schedules comprising day as well as night shifts,” the study concluded.
According to MailOnline, 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.
But an early menopause could also come from the stress of working late at night, as stress hormones are believed to disrupt sex hormones like oestrogen.
Previous evidence suggests that working ‘high-strain’ jobs and those with ‘difficult schedules’ is linked to earlier menopause.
The authors said given the 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.