because it turns out that the way we live can influence the accumulation of amyloid plaques. 因为这证明了我们的生活方式可以影响淀粉样斑块的积累。

　　And so there are things we can do to keep us from reaching that tipping point. 我们可以做许多小事来避免达到临界点。

　　Let's picture your risk of Alzheimer's as a see-saw scale. 不妨把患老年痴呆的风险比作天平。

　　We're going to pile risk factors on one arm, and when that arm hits the floor, you are symptomatic and diagnosed with Alzheimer's. 把可能增加风险的因素放在一端，如果一端触到地面，那么你将患病。并被诊断为老年痴呆。

　　Let's imagine you're 50 years old. 假设你已五十岁。

　　You're not a spring chicken anymore, so you've accumulated some amyloid plaques with age. Your scale is tipped a little bit. 你已不再年轻，随年岁增长你已积累了部分淀粉样斑块。你的天平已经微微倾斜。

　　Now let's look at your DNA. We've all inherited our genes from our moms and our dads. 现在观察一下你的DNA。我们的基因全部遗传自我们的父母。

　　Some of these genes will increase our risk and some will decrease it. 一些基因会增加风险，还有一些会降低风险。

　　If you're like Alice in "Still Alice," you've inherited a rare genetic mutation that cranks out amyloid beta, 如果你像《依然爱丽丝》中的爱丽丝一样，你遗传的一种罕见的基因突变，粗制滥造着β淀粉样蛋白，

　　and this alone will tip your scale arm to the ground. 单单这一点就会使你的天平一端着地。

　　But for most of us, the genes we inherit will only tip the arm a bit. 不过对于大多数人而言，该基因只会使天平稍稍倾斜。

　　For example, APOE4 is a gene variant that increases amyloid, 举个例子，APOE4是一种增加淀粉样蛋白的变异基因，

　　but you can inherit a copy of APOE4 from mom and dad and still never get Alzheimer's, 你可能会从父母那里遗传一份APOE4的基因，不过却不会患上老年痴呆，

　　which means that for most of us, our DNA alone does not determine whether we get Alzheimer's. 这也就意味着对大多数人而言，我们的DNA并不是决定老年痴呆的唯一要素。

　　So what does? We can't do anything about getting older or the genes we've inherited. 那么什么决定呢？我们对于衰老无能为力，也无法决定我们遗传的基因。

　　So far, we haven't changed our brain's destiny. 到现在我们还没有改变我们大脑的宿命。