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

    Dr. Ken 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 genes, not environment, are likely responsible for the late childbirth-long life connection.

    Research has already shown that women who get pregnant and bear children relatively 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 analog 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.

    一項針對200萬人的歷史資料研究表明，如果你的家族成員普遍晚育，那么家族的人可能會普遍長壽。

    鹽湖城猶他大學的肯•R•史密斯博士和同事研究發現，在四五十歲生育的女性更長壽，她們的兄弟也是如此，但兄弟的妻子卻不會這樣，這表明可能會影響晚育與長壽關系的因素是基因，而不是環境。

    史密斯和他的研究小組在發表于《老年醫學：生物科學》雜志上的報告中稱，研究表明，懷孕和生育相對較晚，且沒有利用輔助生殖技術（ART ）的女性在更年期后更長壽。為研究她們的親屬是否也會長壽，研究人員還查閱了出生于1800年至1869年間的11604位猶他州男性居民，以及1670年至1750年間生活在魁北克的6206位男性的資料。所有被調查的男性都至少有一位活到50歲以上的姐妹。

    史密斯在接受記者采訪時稱，被調查女性顯然沒有使用ART技術或現代避孕法，并且在兩種文化背景下（分別為摩門教和天主教）女性都盡量延長生育期，因此這些記錄是研究自然生育的絕佳資料。他在采訪中解釋道：“我們研究的基本屬于一種生物現象。并不是女性故意選擇晚育，而是這恰好反映了她們晚育的能力。”

    通過對這些女性的調查，研究人員發現，晚育確實與長壽有關。對14123位猶他州女性的調查結果顯示，與更早生育的女性相比，41歲至44歲之間生育最后一個孩子的女性在50歲之后的死亡率要低6%，而45歲及以上生育的女性年死亡風險概率則要低14%。

    對4666位加拿大女性的調查結果與之類似。在42歲至44歲半生育孩子會使女性年死亡率降低7%，而在44歲半及以上生育孩子的女性年死亡率則要低17%。

    這些女性的兄弟也從中受益。這對那些至少有三個姐妹，且其中一位姐妹晚育的男性影響最大。在猶他州居民中，這類男性死亡率比其他人要低20%，對魁北克的被調查者來說，死亡率則要低22%。

    史密斯解釋稱，研究結果表明，在兩種性別中，使女性相對晚育的基因都會使人長壽。他補充說，現今研究晚育對壽命的影響很困難，“在當今社會與晚育相似的生理狀態是較晚的更年期。”

    史密斯和同事還將研究晚育和壽命的關系是否與心臟病和癌癥等致人短命的疾病有關。他表示，如果研究結果顯示這并不與特定疾病相關，而卻在全球有更廣泛的影響，這將表明此類基因也許對延緩衰老起到基礎性作用。