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If you want to maintain a sharp memory, you may want to brush up: People who have fewer natural teeth remaining perform more poorly on memory tests, a new study suggests.
Looking at 273 people ages 55 and older, the researchers found a modest but significant relationship between a person's number of natural teeth and his or her performance on memory tests.
The link held when researchers took subjects' ages into account. In other words, it wasn't simply that both teeth and memory abilities tend to disappear with age.
Although the reason for the link isn't entirely clear, the new findings are in line with previous animal and human studies, suggesting that the presence of natural teeth has an impact on cognitive function, and having fewer teeth may be regarded as a risk factor for memory problems in the elderly, according to the researchers, who detailed their findings in the August issue of the European Journal of Oral Sciences.
Animal studies have shown that rats whose teeth were pulled out showed memory and learning problems. The rats that had lost more teeth showed higher neuronal loss, and more damage to the hippocampus, a part of the brain involved in memory formation.
It is possible that losing natural teeth reduces sensory signals that teeth send to the brain, affecting its functions, including memory, the researchers said.
Natural teeth send signals to the brain via a nerve that is responsible for sensation in the face, and for motor functions, such as biting and chewing. Prosthetic teeth, though helpful for eating, lack the nerves and ligament that attach natural teeth to the jaw, potentially resulting in a reduced sensory input to the brain.
It's also possible that a common factor could be responsible for the link between teeth and memory. For instance, gum infections that could lead to tooth loss may also cause inflammation, which may, in turn, cause neuronal death and memory loss, the researchers said.
In the new study, the researchers accounted for other factors that can affect memory — such as participants' years of education, type of occupation and medical history — but the link between teeth and memory remained significant.
Study participants had an average of 22 natural teeth, almost one-third fewer than a complete set of human teeth, which may have caused them to avoid or eat less of certain foods that contain the nutrients necessary for maintaining a strong memory, the researchers said.
One limitation of the study is the small number of participants. Nevertheless, a previous study involving more than 4,000 participants — and that controlled for several lifestyle factors, such as smoking and alcohol intake — found similar results. People with few or no teeth were more likely to have some memory loss, compared with participants who still had many of their natural teeth. That study was published in the journal Behavioral and Brain Functions in 2011.
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譯文
自然牙掉落減少了牙齒發(fā)送到大腦的感官信號(hào)，影響了大腦的功能，這其中可能包括記憶力。
如果你想保持敏銳的記憶力，你可能想要你的牙齒更好: 一項(xiàng)新的研究表明，自然牙齒少的人在記憶測(cè)試中的表現(xiàn)更差。
研究人員研究了273名年齡為55歲及以上的人，他們發(fā)現(xiàn)一個(gè)人自然牙齒數(shù)量的多少與其在記憶力測(cè)試中的表現(xiàn)有著一定的重要聯(lián)系。
當(dāng)研究人員把受試者的年齡考慮進(jìn)來(lái)之時(shí)，這種聯(lián)系就產(chǎn)生了。換句話說(shuō)，牙齒和記憶能力并非隨著年齡的增長(zhǎng)而消失那么簡(jiǎn)單。
研究人員稱，盡管聯(lián)系的原因還不完全清楚，但新的研究成果與以前對(duì)動(dòng)物和人類(lèi)的研究相吻合，這表明自然牙齒的存在影響認(rèn)知功能，有很少的牙齒可能會(huì)被看作是老年人的記憶問(wèn)題的一種危險(xiǎn)因素。8月份出版的《口腔科學(xué)歐洲期刊》詳細(xì)敘述了他們的研究結(jié)果。
動(dòng)物研究已表明，那些被拔掉牙的老鼠記憶認(rèn)知顯現(xiàn)出問(wèn)題。失去牙齒多的老鼠表現(xiàn)出神經(jīng)元受損更高，海馬（參與記憶形成的大腦部分）受損更大。
研究人員說(shuō)，失去自然牙齒很可能會(huì)減少牙齒發(fā)送到大腦的感官信號(hào)，影響了包括記憶力在內(nèi)的大腦功能。
自然牙齒通過(guò)神經(jīng)向大腦發(fā)送的信號(hào)影響面部表情，還會(huì)影響諸如咬和咀嚼等運(yùn)動(dòng)功能。假的牙齒雖然能幫助吃飯,但是沒(méi)有自然牙齒所具有的與下巴相連的神經(jīng)和韌帶, 因而有可能減少了大腦的感覺(jué)輸入。
尋常因素也有可能造成牙齒和記憶力之間的聯(lián)系。研究人員說(shuō)，比如，可能引起牙齒脫落的牙齦感染也會(huì)引起炎癥，這可能反過(guò)來(lái)造成神經(jīng)元死亡和喪失記憶。
在新研究中，研究人員對(duì)有可能影響記憶力的其它因素（如參與者的教育年頭、職業(yè)類(lèi)型以及病史）進(jìn)行了解釋，但牙齒和記憶之間的聯(lián)系仍然明顯。
研究人員說(shuō)，研究的參與者平均有22顆自然牙齒，比一副完整的人類(lèi)牙齒少了幾乎三分之一，這可能使他們避免或少吃某些食物，而那些食物中含有保持良好記憶力所必需的營(yíng)養(yǎng)。
參與者人數(shù)不多是這項(xiàng)研究的一個(gè)局限性。不過(guò)，先前的一項(xiàng)研究有4000多名參與者（而且還控制了幾個(gè)生活方式因素，比如吸煙和飲酒），也發(fā)現(xiàn)了類(lèi)似的結(jié)果。相較于仍有許多天然牙齒的參與者，那些牙齒很少或沒(méi)有牙齒的人更有可能有一些記憶喪失。該研究發(fā)表在2011年的《行為和大腦功能》期刊上。
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