即使是同卵雙胞胎，也會因成長環境與人生經歷不同，而發展出不一樣的特質與習慣

My childhood experience was consistent with research showing that even in identical twins, different qualities and habits emerge as a result of their environment and life experiences.

However, some behaviors and traits are surprisingly driven by inheritance.

**然而，仍有一些行為與特質，出乎意料地深受遺傳影響。**

---

In the late 1970s and early 1980s, investigators at the University of Minnesota studied identical adult twins who were reared apart.

**在 1970 年代末到 1980 年代初，明尼蘇達大學的研究人員研究了一批自小分開撫養、成年後的同卵雙胞胎。**

They found remarkable similarities in many measures of personality, personal interests, and temperament, suggesting that genetics has a much greater impact on taste and character than people realized.

**他們發現，這些雙胞胎在許多個性、興趣與氣質的量表上，出現驚人的相似度，顯示遺傳對一個人的品味與性格的影響，比一般人想像得更大。**

Some of the twin pairs, who hadn’t met since infancy, actually gave their children the exact same name or drove the exact same car in the same color.

**有些自嬰兒時期就未再見面的雙胞胎，竟然給自己的孩子取了一模一樣的名字，或是開著同款同色的車。**

If the twins smoked, they often picked the same brand of cigarette.

**如果他們抽菸，往往也會選擇同一個牌子的香菸。**

---

Genetics are certainly not the whole story when it comes to brain aging.

**然而，談到大腦老化時，基因絕對不是全部的解釋。**

My early research showed that when one identical twin lives a healthier lifestyle (e.g., exercises, eats healthy, and doesn’t smoke), that twin will have better memory abilities, higher scores on neuropsychological tests, and a larger brain.

**我早期的研究顯示，如果一對同卵雙胞胎中，有一位過著更健康的生活型態（例如運動、飲食健康、不抽菸），那位雙胞胎會有較佳的記憶能力、在神經心理測驗中獲得較高分數，且大腦體積也較大。**

Scientists at Washington University in St. Louis found that brain scans of people with a genetic risk for Alzheimer’s show less evidence of the disease in their brains if they exercise regularly.

**聖路易華盛頓大學的科學家發現，具有阿茲海默症遺傳風險的人，如果規律運動，他們的大腦掃描會顯示較少疾病相關的證據。**

A recent study of nearly 30,000 older adults who engaged in a younger-brain lifestyle involving healthy diet, regular physical exercise, an active social life, and stimulating cognitive activity revealed slower memory decline over a 10-year period, even if they had a genetic risk for developing Alzheimer’s disease.

**最近一項涵蓋近三萬名年長者的研究指出，那些實踐「年輕大腦生活型態」的人——包括健康飲食、規律運動、活躍的社交生活，以及持續刺激大腦的活動——在十年間的記憶退化速度較慢，即使他們具有罹患阿茲海默症的遺傳風險也是如此。**

---

DISCOVERY #5 Lifestyle habits affect your brain more than your genes do.

**發現五：生活習慣對大腦的影響，比基因還要大。**

The large-scale longitudinal MacArthur Study defined successful aging as maintaining both cognitive and physical health over the years.

**大型縱貫研究「麥克阿瑟研究」將「成功老化」定義為多年來同時維持良好的認知與身體健康。**

That landmark study showed that for the average individual, nongenetic factors contribute more to successful aging than the DNA we inherit.

**這項具里程碑意義的研究指出，對一般人而言，非遺傳因素對成功老化的貢獻，比我們所繼承的 DNA 還要大。**

Scientists have since uncovered several of these nongenetic factors, like lifestyle choices and environmental influences that are often under our control.

**此後，科學家已找出數種這類非遺傳因素，例如生活型態的選擇與環境影響，而這些往往是我們可以自己掌控的。**

---

When I first began researching the neuroscience of aging, doctors hadn’t yet discovered any genes that contributed to dementia, but we did know that people with a family history of Alzheimer’s have a higher risk of developing it themselves.

**當我一開始研究老化的神經科學時，醫界尚未發現任何與失智症相關的基因，但我們已知道有阿茲海默症家族史的人，本身罹病風險較高。**

In order to understand the genetic connection, I collaborated with scientists from Duke University to study families with several affected relatives.

**為了了解其中的遺傳關聯，我與杜克大學的科學家合作，研究那些家族中有多位成員罹患此病的家庭。**

These collaborations led to the discovery of the first major gene known to influence the risk for Alzheimer’s disease: apolipoprotein E, or APOE.

**這些合作促成了第一個已知會影響阿茲海默症風險之重要基因的發現：載脂蛋白 E，簡稱 APOE。**

---

Detailing the genetics was tricky because you don’t know who will develop Alzheimer’s disease until late in life.

**要釐清基因細節並不容易，因為人在人生後期才會知道自己是否會發展成阿茲海默症。**

Today, we hear a lot more about Alzheimer’s because people are living longer—life expectancy has nearly doubled during the past century, and age is the greatest risk factor for cognitive decline.

**如今我們更常聽到阿茲海默症，部分原因是人類壽命延長——在過去一個世紀裡，平均壽命幾乎翻倍，而「年齡」正是認知退化最大的風險因子。**

Most people are terrified of developing dementia, defined as cognitive decline that leaves the patient dependent on others.

**多數人都害怕自己會罹患失智症——這是一種使患者認知能力退化到必須依賴他人照顧的狀況。**

Alzheimer’s disease accounts for nearly two-thirds of all dementias, and scientists are more motivated than ever to unravel its genetics, because knowing what causes an illness often leads to better treatments and possibly a cure.

**阿茲海默症約占全部失智症的三分之二，因此科學家比以往更加積極地想破解其遺傳機制，因為了解疾病成因，往往能帶來更好的治療方式，甚至有機會找到治癒之道。**

---

Everybody carries one of the three forms, or alleles, of the APOE gene in their DNA, but only one of them—the APOE-4 allele—heightens the risk for Alzheimer’s disease.

**每個人的 DNA 中都帶有三種 APOE 基因型態之一（也就是三種等位基因中的一種），但只有其中一種——APOE‑4 等位基因——會提升罹患阿茲海默症的風險。**

One out of every five people is a carrier of APOE-4, but not all APOE-4 carriers develop the disease, while others who do not have APOE-4 do get Alzheimer’s.

**每五個人當中，就有一人帶有 APOE‑4，但並非所有 APOE‑4 帶因者都會罹病；另一方面，也有人沒有 APOE‑4 卻仍然得到阿茲海默症。**

Therefore, the gene alone does not provide enough information to be a predictive test.

**因此，僅靠這個基因並不足以作為預測疾病的檢測依據。**

However, when we combine someone’s brain scan and their genetic data, we get a more precise picture of their brain health.

**然而，當我們將一個人的腦部掃描與其基因資料結合時，就能得到更精準的大腦健康圖像。**

In fact, it’s now possible to detect subtle evidence of brain aging and Alzheimer’s disease decades before an individual actually develops symptoms.

**事實上，現在已能在一個人出現臨床症狀的數十年前，就偵測到與大腦老化和阿茲海默症相關的細微跡象。**

Subtle evidence of cognitive effects of this genetic risk have even been discovered in children and adolescents who are APOE-4 carriers.

**在帶有 APOE‑4 的兒童與青少年身上，也已發現此遺傳風險對其認知功能造成的細微影響。**

---

The other forms of the gene, APOE-2 and APOE-3, work to keep the brain young, but the mechanism is not clear.

**其他兩種基因型態 APOE‑2 與 APOE‑3 則有助於維持大腦年輕，不過其作用機制仍不明確。**

We do know that the proteins produced by all forms of APOE transport cholesterol in the blood.

**我們所知道的是，所有型態的 APOE 所產生的蛋白質，都負責在血液中運送膽固醇。**