FEW CONDITIONS are as feared as dementia, of which Alzheimer’s is the most common cause. This is mostly because of its insidious(隐匿的；潜伏的) nature, since it strips people of their sense of self(剥夺人们的自我意识) and leaves those who love them caring for a stranger. “Alzheimer’s is me unwinding, losing trust in myself, a butt of my own jokes and, on bad days, capable of playing hunt the slipper by myself, and losing,” wrote the late Sir Terry Pratchett, a novelist who had a rare form of it. “I felt totally alone, with the world receding from me in every direction(从四面八方向后退去).”
很少有疾病像痴呆症那样令人恐惧，其中阿尔茨海默病是最常见的原因。这主要是因为其隐匿的性质，因为它剥夺了人们的自我意识，让爱他们的人照顾一个陌生人。已故的小说家特里·普拉切特爵士曾写道：“阿尔茨海默病就是我自我瓦解，失去对自己的信任，成为自己笑话的笑柄，在糟糕的日子里，能独自玩‘找拖鞋’游戏还输了。”他患有一种罕见的痴呆症。“我感到完全孤独，世界从四面八方离我而去。”
It is also dreaded(令人恐惧的) because many believe it is becoming far more common and so will inevitably strike them or those closest to them. Some epidemiologists in the field seem only to fan those fears(煽动那些恐惧). Models predict that the number of people suffering from dementia may triple(增加两倍，增至三倍) to 153m by 2050 as societies age. In truth, the outlook is cheerier than that, especially in rich countries where, if adjusted for age(省略条件句（if + 过去分词）), the risk of getting dementia has dropped sharply in recent decades. Most models assume these declines will not continue, or will even reverse. A mountain of new evidence shows that need not be.
它还令人恐惧，因为许多人认为它正变得越来越普遍，因此将不可避免地降临到他们或他们最亲近的人身上。该领域的一些流行病学家似乎只是在煽动这些恐惧。模型预测，随着社会老龄化，到2050年痴呆症患者人数可能增加两倍，达到1.53亿。事实上，前景比这要乐观，尤其是在富裕国家，如果按年龄调整，痴呆症风险在近几十年已大幅下降。大多数模型假设这些下降不会持续，甚至可能逆转。大量新证据表明并非如此。
Recent studies point out the numerous ways in which people are already reducing their risk of dementia. Many are lifestyle changes that you already know you should be making, such as eating healthily, exercising more and keeping your brain active. Others are medical interventions(干预措施), such as treating hearing loss, depression, high blood pressure and high cholesterol. But getting people to adopt, and then stick to(坚持), healthy habits is hard. It does not help that, ideally, you should be working out more and boozing less for many years before your brain will thank you.(更糟的是，理想情况下，你应该在多年内多锻炼、少喝酒，然后你的大脑才会感谢你。)
最近的研究指出了人们已经在降低痴呆风险的众多方法。许多是生活方式改变，你已经知道应该做，比如健康饮食、多锻炼和保持大脑活跃。其他是医疗干预，如治疗听力损失、抑郁、高血压和高胆固醇。但让人们养成并坚持健康习惯很难。更糟的是，理想情况下，你应该在多年内多锻炼、少喝酒，然后你的大脑才会感谢你。