If having children late in life runs in your family, longevity¹ may as well, according to a new analysis drawing from historical data from more than 2 million people.

Dr. Ken² R. Smith of the University of Utah, Salt Lake City, and his colleagues found that women who bore children in their 40s and 50s lived longer, and so did their brothers. But their brothers' wives didn't, suggesting that genes³, not environment, are likely responsible for the late childbirth-long life connection.

Research has already shown that women who get pregnant and bear children relatively⁴ late -- without the help of assisted reproduction technology (ART) -- live longer after menopause, Smith and his team explain in their report in the Journal of Gerontology: Biological Sciences. To learn whether their relatives might live longer too, the researchers looked at records for 11,604 male Utah settlers born between 1800 and 1869 and 6,206 men living in Quebec between 1670 and 1750. All of the men had at least one sister who lived to be at least 50 years old.

These records offer a perfect opportunity to study natural fertility, because women obviously weren't using ART or modern contraception, and in both cultural settings (Mormon and Catholic, respectively) were expected to keep bearing children for as long as they could, Smith told the reporters. "We're observing something that's basically a biological phenomenon," he explained in an interview. "It's not women choosing to have kids late in life, it just simply reflects their ability to have kids late in life."

Among these women, the researchers found, late childbirth indeed conferred longer life. In the sample of 14,123 Utah women, those who had their last child between age 41 and 44 were 6 percent less likely to die during any year after 50 than were women who had children earlier. For those who had babies at 45 or later, annual mortality risk was 14 percent lower.

For the Canadian group of 4,666 women, the numbers were similar. Having a child between 42 and 44.5 reduced annual mortality by 7 percent, and it was 17 percent lower for women who had a child at 44.5 years of age or later.

And their brothers benefited too. The largest effect was seen among men who had at least three sisters, and one sister who had a child late in life. Among the Utah settlers, these men had a 20 percent lower mortality rate; for the Quebec group, mortality was 22 percent lower.

The findings suggest that the genes that allow women to continue bearing children relatively late are related to longevity in both sexes, Smith explained. Today, he added, it's tough to study the effects of late childbirth on longevity. "The modern day sort of analog⁵ to the late fertility would be late natural menopause," he said.

Smith and his colleagues are now going to investigate whether late childbirth and longevity are related to life-shortening illnesses like heart disease and cancer. If it turns out there's no disease-specific relationship, but instead a more global influence, that would suggest these genes may have a fundamental role in slowing the aging process, he said.

一项针对200万人的历史资料研究表明，如果你的家族成员普遍晚育，那么家族的人可能会普遍长寿。

盐湖城犹他大学的肯•R•史密斯博士和同事研究发现，在四五十岁生育的女性更长寿，她们的兄弟也是如此，但兄弟的妻子却不会这样，这表明可能会影响晚育与长寿关系的因素是基因，而不是环境。

史密斯和他的研究小组在发表于《老年医学：生物科学》杂志上的报告中称，研究表明，怀孕和生育相对较晚，且没有利用辅助生殖技术（ART ）的女性在更年期后更长寿。为研究她们的亲属是否也会长寿，研究人员还查阅了出生于1800年至1869年间的11604位犹他州男性居民，以及1670年至1750年间生活在魁北克的6206位男性的资料。所有被调查的男性都至少有一位活到50岁以上的姐妹。

史密斯在接受记者采访时称，被调查女性显然没有使用ART技术或现代避孕法，并且在两种文化背景下（分别为摩门教和天主教）女性都尽量延长生育期，因此这些记录是研究自然生育的绝佳资料。他在采访中解释道：“我们研究的基本属于一种生物现象。并不是女性故意选择晚育，而是这恰好反映了她们晚育的能力。”

通过对这些女性的调查，研究人员发现，晚育确实与长寿有关。对14123位犹他州女性的调查结果显示，与更早生育的女性相比，41岁至44岁之间生育最后一个孩子的女性在50岁之后的死亡率要低6%，而45岁及以上生育的女性年死亡风险概率则要低14%。

对4666位加拿大女性的调查结果与之类似。在42岁至44岁半生育孩子会使女性年死亡率降低7%，而在44岁半及以上生育孩子的女性年死亡率则要低17%。

这些女性的兄弟也从中受益。这对那些至少有三个姐妹，且其中一位姐妹晚育的男性影响最大。在犹他州居民中，这类男性死亡率比其他人要低20%，对魁北克的被调查者来说，死亡率则要低22%。

史密斯解释称，研究结果表明，在两种性别中，使女性相对晚育的基因都会使人长寿。他补充说，现今研究晚育对寿命的影响很困难，“在当今社会与晚育相似的生理状态是较晚的更年期。”

史密斯和同事还将研究晚育和寿命的关系是否与心脏病和癌症等致人短命的疾病有关。他表示，如果研究结果显示这并不与特定疾病相关，而却在全球有更广泛的影响，这将表明此类基因也许对延缓衰老起到基础性作用。

Vocabulary:

run in the family: 世代相传

Mormon：摩门教，崇尚一夫多妻制，与之相对的Catholic（天主教）信奉一夫一妻制。