Working long hours in a stressful job can hasten the onset of menopause by at least a year, doctors have warned.
Women who regularly work more than 48 hours a week tend to go through menopause earlier than those who put in shorter hours, research shows.
High levels of stress in the workplace can also lead to periods stopping earlier than would normally be expected.
However, being highly educated or having a repetitive job lengthened the child-bearing years.
It is thought that hormonal changes brought on by the strain of putting in long hours or holding down a stressful job affect a woman's reproductive health.
The warning, from French doctors, comes just weeks after other research found that working long hours in pregnancy can greatly increase the risk of miscarriage.
The study of more than 7,000 expectant nurses found that those who worked more than 40 hours a week were 50 percent more likely to miscarry.
The findings come as more and more women delay motherhood, with almost half of the 720,000 births each year in Britain being to women aged 30-plus.
The research on menopause, carried out at Versailles University, looked at the health and lifestyle of more than 1,500 women in their 50s.
It found that those who worked at least 48 hours a week were more likely than those doing shorter hours to go through menopause before the average age of 52.
For those with stressful jobs -- in which they felt constant pressure to rush, do several things at once and were frequently interrupted when carrying out tasks -- menopause tended to hit at 51.
In women who were suffering from depression, the effects of long working days were even greater.
They were twice as likely to go through the menopause before they reached 52.
Smoking was also found to have a big effect, with those who smoked more than 10 cigarettes a day going through menopause at the age of 50, the American Journal of Epidemiology reported.
It is thought that long hours and stress affect levels of hormones key to a woman's reproductive cycle, while smoking causes the eggs to deteriorate more quickly than normal.
Genetics also play a large role in the timing of the menopause, with many women experiencing it at a similar age to their mother and sisters.
Although the average age in the U.K. for menopause -- defined as the time when periods have stopped for 12 months -- is 52, 1 percent of British women go through it before they reach 40.
Source: Daily Mail; London (UK). Provided by ProQuest Information and Learning. Powered by YellowBrix.
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