Do Your Genes Determine How Long You’ll Live?基因決定壽命？

伊娃·哈姆魯德 譯/鄧夢寒

The average life expectancy in many developed countries is around 80 years old. Some individuals have famously lived for much longer—the oldest person who ever lived was 122 years old！

Whilst death is inevitable， longevity varies drastically between individuals. What is the secret to a long life？ Is our longevity already encoded in our DNA or is it determined by our lifestyle？

We asked 11 experts in ageing， cell biology and genetics： “Is longevity primarily determined by genetics？” Here’s what we found out.

Longevity in comparison to what？

Experts had two different interpretations of the question：

1） “Is the longevity of humans as compared to other species primarily determined by genetics？”

2） “Is the longevity of some individual humans as compared to other humans primarily determined by genetics？”

Genetics determines cross-species lifespans

Different animal species have very different lifespans. The Greenland shark is able to live to be 400 years old， whilst some species of mayfly only live for 5 minutes. The reason for these differences is genetics.

Professor David Gems， an expert in ageing from University College London， says， “The question could mean： are the upper limits of longevity in humans as a species primarily determined by genetics， in which case the answer is ‘near certain’. For example， the maximum lifespan of human beings is approximately twice that of our closest relatives among the higher primates， such as chimpanzees and gorillas.”

Lifestyle is more important than genes across humans

Dr Gems says， “If one takes [the question] to mean： are the differences in lifespan between individual people primarily determined by genetics， then the answer is ‘extremely unlikely’.” Most of the experts agreed with Dr Gems. Whilst genetics plays a role in longevity， it is not the primary determining factor.

Professor Dame Janet Thornton， an expert in anti-ageing and cell biology and previous director of the European Bioinformatics Institute says that “genetics accounts for less than 30 percent of the effect—but it is true that longevity tends to run in families—i.e. some families have many very old people.”

It can be difficult to determine if the existence of families with many very old people is due to genetics or environment， as often family members adopt similar diets and lifestyles. Studying the DNA of these long-lived people could tell us more.

Professor Ken Parkinson， an expert in anti-aging and oncology from Queen Mary University London says， “Many groups are trying to understand this by sequencing the DNA of centenarians and supercentenarians and performing genome-wide analysis.”

The lifestyle effect on longevity is clearly apparent when we look at how average life spans have increased over hundreds of years due to increased accessibility of clean water， food and medical care.

Counter-intuitively， it has been shown that restricting calorie intake could be linked to longevity in humans. Another lifestyle factor is exercise. Even light exercise for 15 minutes a day has been shown to increase life expectancy by around 3 years.

Individual longevity between humans is affected by genetics， but not primarily. Professor Lorna Harries， an expert in genetics and cell biology from Exeter University summarizes that “genetics can set you up for a long life， but you then need to do the right things to realize that.”

The takeaway

Differences in longevity between humans is not primarily determined by genetics. Regular exercise and a healthy diet may be the “secret” to longevity.

許多發達國家的人口平均壽命為80歲左右。有些人因活得特久而出名——有史以來最長壽的人活了122歲！

死亡不可避免，但壽命差異巨大。長壽的秘訣是什么？壽命已編入我們的DNA中，還是由我們的生活方式所決定呢？

就“壽命是否主要由基因決定？”這一問題，我們咨詢了老齡化、細胞生物學和基因學領域的11位專家，總結如下。

壽命長短的比較對象是什么？

專家針對這個問題按兩種不同情況做了解釋：

1）“人與其他物種相比，壽命長短主要由基因決定嗎？”

2）“人與人相比，壽命長短主要由基因決定嗎？”

基因決定不同物種的壽命

不同的動物物種壽命差異極大。格陵蘭睡鯊可以活400年，而有些種類的蜉蝣只能活5分鐘。這些差別由基因決定。

英國倫敦大學學院的老齡化專家戴維·格姆斯教授說：“這個問題可能相當于：人類作為一個物種，其壽命上限是否主要由基因決定——這一問題的答案是：‘幾乎可以肯定’。舉個例子，與高等靈長類動物中人類的近親（如黑猩猩和大猩猩）相比，人類的最長壽命大概是它們的兩倍。”

人與人相比，生活方式比基因更重要

格姆斯博士說：“如果有人認為[這個問題]的意思是：人與人之間壽命長短不同是否主要由基因決定，那么答案是‘極不可能’。”大多數專家贊同格姆斯博士的觀點。盡管基因與壽命有關，但不是主要的決定因素。

抗衰老和細胞生物學專家、歐洲生物信息研究所前所長、女爵士珍妮特·桑頓教授說，“ 基因的作用占了不到30%——但是長壽確實往往跟家族有關，例如有些家族有很多長壽的人”。

家族擁有很多長壽者是由基因還是環境因素決定的，這一點可能很難確定，因為家庭成員的飲食和生活方式通常都相似。研究這些長壽者的DNA或許會有更多發現。

倫敦瑪麗女王大學的抗衰老和腫瘤學專家肯·帕金森教授說：“ 許多研究團隊正試圖通過對百歲老人和超百歲老人的DNA進行測序并開展全基因組分析來了解這一點。”

數百年來，由于凈水、食物和醫療服務的普及，人類平均壽命延長，生活方式對壽命的影響由此顯而易見。

令人意外的是，有研究表明，限制卡路里攝入可能也與人類長壽相關。另一個跟生活方式有關的因素是運動。已有研究顯示，即使每天輕度運動15分鐘，也可以增加大約3年的壽命。

基因會影響人類個體壽命長短，但并非主要因素。埃克塞特大學基因學和細胞生物學專家洛娜·哈里斯教授總結說，“基因可能為你打下了長壽的基礎，但你還需要做正確的事才能達到長壽的目標”。

要點

基因并不是決定人與人之間壽命不同的主要因素。經常鍛煉和健康飲食或許才是長壽的“秘訣”。? ? ? ? ? ? ? ? ? ? ? ? ? ? ?□