Menopause will be delayed, possibly disappear as women give birth later: study

TORONTO -- As more mothers have children later on in life, Ontario researchers say menopause will become delayed and possibly disappear altogether.

In a new paper published in the journal BMC Women’s Health on Friday, researchers from McMaster University argue that changing social values and improvements in science, medical testing, and health care have allowed an increasing number of women around the world to delay childbirth.

For example, the researchers said the average age at which a woman gives birth in Canada has increased from 23 to 30 in just the last 50 years.

“This massive change has to be reflected in the reproductive age of women. We are doing in 50 years what would have taken nature thousands of years,” Rama Singh, a biology professor and co-author of the study, said in a press release.

As a result of this delay in childbirth, Singh and his fellow researchers said menopause, too, will occur later and even possibly cease to exist.

“It is going to happen. It is happening because of social change. Women have control now,” Singh said.

To support their theory, the research team analyzed data on 747 middle-aged women included in the Study of Women’s Health Across the Nation (SWAN). That 12-year U.S. study asked women from several ethnicities, including Afro-American, Chinese, Japanese, Caucasian, and Hispanic, about their health and when they reached menopause.

“We used the data to ask the question whether women differ within any ethnic group when they go into menopause and whether there are differences between different ethnic groups. Because if there are differences within and between populations, that means to us, that menopause is not one thing, fixed, a done deal, determined by the same genes in every population,” Singh explained during a telephone interview with CTVNews.ca on Friday.

In studying the collected data, the McMaster University researchers did indeed find that there were significant variations in the onset of menopause that were not linked to specific ethnicities.

“The fact that there is variation between individuals, and within and between populations and ethnic groups, tells us that menopause is a changing, evolving trait that is still very dynamic,” Singh explained.

In 2013, Singh made international headlines for suggesting that women went into menopause because “men have long preferred younger mates.” He said over millennia, older women who weren’t having children accumulated infertility mutations that developed into what is now known as menopause.

“Ours was a very radical explanation, which was that it has nothing to do with something internal, it had to do with human behaviour, how we choose mates,” he said.

That earlier study received mixed reactions with some evolutionary biologists and anthropologists who argued the opposite in that men chose younger mates because older women were less fertile.

However, Singh said he believes the selection of mates is what ultimately determines when menopause occurs in a woman.

“If we accept that in our society, for many reasons, there is a preference of younger women, meaning that older women don’t reproduce, then mutations affecting fertility will accumulate,” he said.

Singh and his research team said menopause will become delayed or disappear because nature will develop genetic variations that will favour longer fertility.

As for when this will occur, Singh said he thinks the difference will likely become evident within the span of a generation as mothers who give birth later in life pass on those tendencies to their own children. 

“If there is no natural genetically controlled boundary, and if menopause means infertility of women, and if more and more women in older age reproduce, that means the fertile genes are pushing the boundary,” he said.

Singh stressed, however, that just because there is the potential for menopause to be delayed or even eliminated, it doesn’t mean it will happen overnight.

“Menopause did not come yesterday, so it’s not going to go away tomorrow,” he said.

The change will also only occur, he said, if people continue to have children later in life.

“If we change our habits, marry late, have children late, then it makes sense that menopause will also become late.”