If you’re looking for another reason to appreciate your sister, here’s one with a scientific twist.
Research suggests brothers may live longer when their sisters can pull off something extraordinary later in life.
But that longevity boost doesn’t seem to extend to spouses — a sign, scientists say, that the benefit comes from genes rather than shared lifestyle.
Past research has shown that women who have children in their 40s and 50s without fertility treatments tend to live longer after menopause than those who stop childbearing earlier.
One study even found that women who had their last child after age 33 had twice the odds of reaching 95 or older compared with those whose final birth came by age 29.
Scientists have long wondered whether a mother’s ability to have children later in life could signal potential benefits for other family members — like, for example, her brothers.
To find out, researchers looked at two historical populations.
One dataset included 1.6 million Utah Mormon pioneers and their descendants, born between 1800 and 1869. The other tracked 400,000 residents of heavily Catholic Quebec from 1608 to 1850.
In both communities, modern birth control and fertility treatments didn’t exist, and natural family planning was generally frowned upon — making it easier to track genuine late-life fertility in large families.
The researchers found that brothers with three or more sisters — including at least one who gave birth at 45 or older — were up to 22% less likely to die in any given year after age 50 compared with men who had no late-fertile sisters.
By contrast, the brothers’ wives didn’t enjoy longer lives, suggesting that the genes allowing women to have children later in life may also influence longevity in men.
“If you have a female relative who had children after age 45, then there may be some genetic benefit in your family that will enhance your longevity,” Ken R. Smith, a demographer and the study’s lead author, said in a statement.
The study also confirmed earlier findings that women who give birth later in life tend to live longer.
Among Utah pioneer women, those who had their last baby between ages 41 and 44 cut their risk of dying after 50 by 6%. Giving birth at 45 or older slashed it by 14%.
In Quebec, the pattern held. Women delivering their final child between 42 and 44½ saw a 6% reduction in mortality after 50, while those who wrapped up childbearing at 44½ or older enjoyed a 17% lower risk.
And while doctors still label 35 “advanced maternal age,” natural pregnancies well beyond that aren’t as rare as you might think.
In 2020 alone, nearly 1,000 American women aged 50 or older gave birth, according to the CDC.
Some go even further: In Germany, 66-year-old Alexandra Hildebrandt delivered her 10th child earlier this year without fertility drugs.
This trend reflects a broader pattern of American women waiting longer to have children.
In 2023, the average age of first-time mothers in the US reached 27.5, up from just 21.4 in 1970, according to federal data.
That same year, the average age for all mothers climbed to nearly 30, rising from 28.7 in 2016.
