视力、听力减退可能导致认知能力下降
我不时会听到有人(包括我自己)说“我的脑子超负荷”。考虑到大脑承担的数不清的复杂任务，包括让你能够学习、规划、记忆、交流、看、听和闻，这不足为奇。
Perhaps also not surprising, a growing number of studies have linked compromised sensory functions like poor vision and hearing to a decline in cognitive abilities. The brain, it seems, can do only so much, and when it must struggle to make sense of the world – from reading the words on a page to understanding the spoken word – it may be less able to perform other important tasks.
或许同样不足为奇的是，越来越多的研究把视力和听力下降等感官功能受损和认知能力下降联系在了一起。似乎大脑能力有限，当它必须挣扎着理解外部世界——从看懂书面文字到理解口头语言——它进行其他重要任务的能力可能会减弱。
While a cause-and-effect relationship has yet to be established, evidence is gradually increasing to suggest that uncorrected deficits in vision and hearing can accelerate cognitive decline.
尽管还没确定两者之间的因果关系，但越来越多的证据表明，未得到修复的视力和听力受损可能会加剧认知能力的下降。
National statistics demonstrate the importance of this relationship. The number of Americans with poor vision, often undetected among older adults, is expected to double by 2050; hearing loss – mostly untreated or undertreated – afflicts nearly two-thirds of adults over 70; both vision and hearing impairment occur in one person in nine age 80 and older (fewer than one in five have neither), and the prevalence of dementia is now doubling every 20 years.
全国性统计数据显示出了这种关系的重要性。到2050年，美国视力下降的人数预计会翻倍，而这在上了年纪的人群中是经常未被察觉的一个问题;听力受损者在70岁以上的人群中占近三分之二，他们大多未得到治疗或治疗不充分;80岁及以上的人群中，视力和听力都下降的比例为九分之一(两者均未受损的不到五分之一)，痴呆症的发病率现在每20年翻一倍。
The latest study, published in August in JAMA Ophthalmology, found that among a representative sample of nearly 3,000 older Americans and a second sample of 30,000 Medicare beneficiaries, poor vision was associated with poor cognition.
8月发表在《眼科学纪要》(JAMA Ophthalmology)上的一项最新研究发现，在由3000名美国老年人组成的代表性样本和3万名联邦医疗保险(Medicare)的受益者组成的另一份样本中，视力不良和认知能力差存在关系。
The two data sets used different measurements of cognitive abilities like memory, orientation and planning, and the consistency of their findings suggests that the association between vision impairment and compromised brain function is real, the researchers concluded.
两个数据集用不同的方法对记忆力、方向感和规划能力等认知能力进行了衡量，得到了一致的结果。研究人员断定，这表明视力受损和大脑功能受损之间的关联是真实存在的。
The lead author, Dr. Suzann Pershing, ophthalmologist at Stanford University School of Medicine, said that “while this association doesn’t prove vision loss causes cognitive decline, intuitively it makes sense that the less engaged people are with the world, the less cognitive stimulation they receive, and the more likely their cognitive function will decline.”
第一作者、斯坦福大学医学院(Stanford University School of Medicine)眼科专家苏珊·珀欣(Suzann Pershing)说，“尽管这种关联无法证明视力下降导致认知能力下降，但它直观地解释了人们与外部世界的互动越少，他们受到的认知刺激越少，认知功能下降的可能性越大。”
An earlier study of 625 elderly people at the University of Michigan by Dr. Mary A.M. Rogers and Kenneth M. Langa found that those with poor vision had a 63 percent greater risk of developing dementia over a period of eight and a half years. Those with poor vision who did not visit an ophthalmologist were five times more likely to experience cognitive decline and nine and a half times more likely to develop Alzheimer’s disease.
玛丽·A·M·罗格斯(Mary A.M. Rogers)和肯尼斯·M·兰加(Kenneth M. Langa)早前在密歇根大学(University of Michigan)对625名老年人进行的一项研究发现，视力下降的人在八年半的时间里患痴呆症的风险要高出63%。视力下降却不看眼科医生的人认知能力下降的几率要高出五倍，患阿茲海默症的可能性高出9.5倍。
“This is not necessarily a one-way relationship,” Dr. Pershing said. “If you improve the vision of people with cognitive impairment, they can function better.”
“这不一定是一种单向关系，”珀欣说。“如果改善认知能力受损者的视力，它们的功能都会提升。”
Likewise with hearing, where there is stronger evidence that hearing loss can speed cognitive decline. However, it is not yet known whether wearing properly adjusted hearing aids can decrease the risk of dementia or slow its onset. A study sponsored by the National Institute on Aging should show in five years whether using hearing aids can help preserve brain function in people with hearing loss as they age.
听力也是如此，有更有力的证据证明，听力受损会加速认知能力的下降。不过，尚不清楚佩戴合适的助听器能否降低患痴呆症的风险或延缓它的发生。美国国家老龄问题研究所(National Institute on Aging)资助的一项研究应该能在五年后证明，佩戴助听器能否帮助保护那些因年老而出现听力损伤的人的脑部功能。
Dr. Frank R. Lin, otolaryngologist at the Johns Hopkins Center on Aging and Health, said “the potential impact is huge,” especially now. Companies like Apple and Samsung are expected to soon market hearing aids that cost perhaps $50 to $300 instead of $5,000 a pair, making this assist accessible to many more people. (Already, Dr. Lin said, “Costco has made a huge dent in affordability,” lowering the cost of hearing aids fitted and serviced by well-trained audiologists.)
约翰斯·霍普金斯老龄与健康研究中心(Johns Hopkins Center on Aging and Health)的弗兰克·R·林博士(Frank R. Lin)表示，“潜在的影响是很大的”，尤其是现在。苹果(Apple)和三星(Samsung)等公司有望很快推出可能仅需50至300美元的助听器，让更多人负担得起这种设备(林博士说，“好市多[Costco]已经极大减轻了人们的经济负担”，降低了由训练有素的听力学家装配和提供服务的助听器的成本)。
Meanwhile, here’s what we already know. A prospective study of 1,984 older adults directed by Dr. Lin found that those who initially had hearing loss were 24 percent more likely than their age-mates with normal hearing to experience cognitive decline within six years.
与此同时，我们已经知道了以下这些情况。林博士主持的一项对1984名老年人进行的前瞻性研究发现，在实验之初就有听力损伤的人在六年内出现认知能力下降的几率比听力正常的同龄人高24%。
Their cognitive abilities declined up to 40 percent faster than others with normal hearing. They had greater problems with brain functions like thinking and memory, developing them on average three years earlier than people their age with normal hearing. And the more severe their hearing loss at the start of the study, the greater their cognitive loss over time.
他们的认知能力下降的速度比听力正常的同龄人快40%。他们比听力正常的同龄人平均早三年出现思考和记忆等更严重的脑功能问题。在实验之初听力受损情况更严重的人，在一段时间后认知能力受损的程度也更严重。
“Older adults with hearing loss face an increased risk of dementia even when you control for diseases like diabetes and high blood pressure,” Dr. Lin said in an interview. “So we think they’re causally related.”
“听力受损的老年人面临更高的患痴呆症风险，尽管排除了糖尿病和高血压等疾病的影响，”林博士在接受采访时说。“所以我们认为，它们之间存在因果联系。”
He suggested three ways that may explain how poor hearing and dementia are linked. One involves “cognitive load” — when you can’t hear well, the brain receives garbled signals, forcing it to work harder to derive meaning from the message.
他认为有三种方法可以解释为什么听力不好和痴呆症有关。一个解释涉及“认知负荷”——你听不清楚时，大脑接收的是错乱的信号，迫使它更努力地工作，试图弄清那条信息的意思。
Another mechanism may be that people who can’t hear well tend to become socially isolated, which results in diminished cognitive stimulation and cognitive loss.
另一个机制可能是那些听不清的人往往更孤僻，那会导致认知刺激减少，认知能力受损。
Perhaps most important is a third possible explanation involving brain structure; hearing loss results in a faster rate of brain atrophy mostly over the hearing portion of the brain, which is also involved in functions like memory, learning and thinking.
可能最重要的是第三种可能的解释，它与大脑结构有关。听力损伤会导致大脑萎缩速度加快，主要是大脑的听力部分，而这个部分也跟记忆、学习和思考等功能有关。
At Washington University in St. Louis, Jonathan Peelle and colleagues have shown through functional M.R.I. studies that even people with mild hearing loss “recruit more of their frontal cortex,” which means that the part of the brain needed for thinking and decision-making is overworked when trying to understand speech.
圣路易斯华盛顿大学(Washington University)的乔纳森·皮尔(Jonathan Peelle)和同事们通过功能性核磁共振研究发现，即使是那些具有轻微听力障碍的人“也需要更多的使用自己的额皮质”，那就意味着大脑需要用来进行思考和决策的部分因努力理解讲话而被过度使用。
“Even in young adults with clinically normal hearing,” Dr. Peelle said, “just a small decline in how well they hear engages more of their frontal cortex.” When hearing loss is advanced, studies have shown that the auditory cortex shrinks, which may diminish the brain’s ability to perform tasks other than hearing, he said.
皮尔博士表示，“即使是那些被临床判定听力正常的年轻人，哪怕听力略微下降，也会更多地使用额皮质。”他还说，多项研究表明，听力损伤加重后，听觉皮质会萎缩，那可能会降低大脑完成听力之外的其他任务的能力。
While the cost-effectiveness of regular screening programs for vision and hearing in older adults has yet to be demonstrated, experts strongly recommend periodic exams to pick up correctable problems that may diminish the risk of dementia and would certainly improve quality of life.
虽然老年人定期进行视力和听力筛查的成本效用尚待确认，但专家们强烈建议定期进行检查，以便发现可纠正的问题，从而可能降低患痴呆症的风险，且无疑能提高生活质量。
The American Academy of Ophthalmology recommends a comprehensive eye exam every two to four years for people aged 40 to 54 with no symptoms or risk factors for vision loss, increasing to every one to three years for those aged 55 to 64, and every year or two thereafter. The exams can help to preserve vision by detecting correctable or treatable problems like glaucoma, cataracts and age-related macular degeneration.
美国眼科学会(American Academy of Ophthalmology)建议40岁至54岁没有任何视力损伤症状或风险的人每二至四年进行一次全面眼部检查，55岁至64岁的人每一至三年检查一次，之后每一至两年检查一次。那些检查可以帮助保护视力，因为通过它们可以查出青光眼、白内障以及老年性黄斑变性等可以矫正或治疗的问题。
The American Speech-Language-Hearing Association recommends a hearing test “at least every decade through age 50 and every three years thereafter.” As Dr. Lin explained, hearing loss can occur so gradually that people don’t recognize the problem until it is well advanced. Also, there is no harm done in getting tested.
美国演讲语言听力协会(American Speech-Language-Hearing Association)建议“50岁之前至少每十年进行一次听力检查，之后每三年进行一次”。林博士表示，听力损伤进展得十分缓慢，人们只会在它非常严重时才会发现。而且，检查一下也没什么坏处。
