The age at which women go through menopause depends a lot on when their relatives did, according to new study findings.
Specifically, women whose mothers or sisters experienced menopause by age 45 were roughly 6 times more likely to do the same. Women who underwent menopause at a relatively late age - 54 or older - were also 6 times more likely to have seen the same thing happen to their mothers, and twice as likely to see it in their sisters.
But age of menopause is not entirely inherited, the authors found - a significant component also depends on so-called environmental factors.
"Genes have an important effect on age at menopause, but lifestyle also matters, and so women can affect their age at menopause by their behaviors," study author Danielle Morris at the Institute of Cancer Research in the UK told Reuters Health.
Scientists know that certain aspects of a woman's environment directly impact her age at menopause, Morris explained - for instance, women who smoke tend to undergo menopause roughly 1-2 years earlier than former or non-smokers. Women who have never given birth also experience menopause earlier, she said.
Age at menopause is an essential aspect of fertility, Morris and her team write in the journal Menopause, since a woman's ability to conceive ends roughly 10 years before she experiences menopause. Previous research has also found that women who experience menopause relatively late in life have a higher risk of breast and endometrial cancers, and a lower risk of cardiovascular disease.
According to the National Institute on Aging, 51 is the average age at which a woman reaches menopause, or has her last period. But some women have their last period in their 40s and some have it later in their 50s.
To investigate how much of a woman's age at menopause is inherited, Morris and her team compared women who were more or less related, reasoning that different relatives will share different amounts of genes and their environment.
"For example, if identical twins have more similar menopausal ages than non-identical twins, then this suggests that genes are important because identical twins have more genes in common than non-identical twins," said Morris in an email.
"Similarly, if sisters have more similar menopausal ages than mothers and daughters, then this (suggests) that environment is important, because sisters have the same amount of genes in common as mothers and daughters do, but sisters tend to have more similar lifestyles than mothers and daughters."
The sample came from a large study designed to investigate the causes of breast cancer among women living in the UK. Among those participants, the researchers selected 2,060 women between the ages of 31 and 90 who had a first-degree relative who was also participating in the same study.
Both early and late menopause appeared to run in families, the authors found - but so did usual-age menopause, they note. Specifically, women whose sisters and mothers underwent menopause during a typical age were between 2 and 7 times more likely to do the same.