FRIDAY, Aug. 26, 2016（合众国际社UPI）【摘要】一项新的研究报告说，常坐沙发看电视（沙发土豆Couch potatoes）有相当高的罹患老年痴呆症的风险。
研究人员发现，很少运动锻炼的老年人患痴呆的风险比那些经常参加中或大量体力活动的老年人高50%。
洛杉矶加利福尼亚大学的老年痴呆症和老年痴呆症护理计划的医疗主任高级研究员Zaldy Tan说“不需要大量密集的体力活动可减少老年痴呆症的风险”，”即使是有一些、适量的都是好的”。
对于适度的体力活动-美国疾病控制和预防中心解释说这些包括快走、骑自行车一小时少于10英里，舞厅跳舞或园艺等活动。
这项研究由联邦政府健康研究项目资助，涉及约3700名参与者，始于1948，年龄都是60岁以上。研究人员记录了参与者的锻炼时间，并跟踪调查超过十年。其中有236人患上了痴呆症。
研究结果显示，75岁或以上的老年人运动具有最好的保护性，可减少老年痴呆症的发病。
研究报告的作者说，随着年龄的增长大脑会收缩。参与者的大脑扫描显示，经常锻炼的人比那些久坐的人有更大的脑容量。
研究者表示尽管在机理上似乎有些模糊不清的地方，鉴于运动没有任何伤害，并有一定的好处，病人和他们的家庭应当帮助他们改善体力活动”。
不管怎样，Boustani说为保持大脑健康，规定适当强度的体育活动是必要的，方法如--每天徒步5000步一个月左右，以后可增加到10000步。
研究结果在线发表于近日的《老年期刊：医学科学》。
FRIDAY, Aug. 26, 2016 -- Couch potatoes have a higher risk of developing dementia in old age, a new study reports.
Seniors who get little to no exercise have a 50 percent greater risk of dementia compared with those who regularly take part in moderate or heavy amounts of physical activity, the researchers found.
Moderate physical activity can include walking briskly, bicycling slower than 10 miles an hour, ballroom dancing or gardening, according to the U.S. Centers for Disease Control and Prevention.
"It doesn't require intensive physical activity to decrease risk of dementia," said senior researcher Dr. Zaldy Tan. He is medical director of the Alzheimer's and Dementia Care Program at University of California, Los Angeles. "Even moderate amounts are fine."
Study participants aged 75 or older gained the most protective benefit from exercise against the onset of dementia, the findings showed.
"The message here is that you're never too old to exercise and gain benefit from it," Tan said. "These patients derive the most benefit from exercise because they are the ones who are at the age of greatest risk for dementia."
Brain scans of participants showed those who exercise are better able to withstand the effects of aging on the brain, the study authors said.
With age, the brain tends to shrink. But people who regularly exercised tended to have larger brain volumes than those who were sedentary, Tan and his colleagues found.
The new study involved about 3,700 participants in the Framingham Heart Study, a federally funded health research project begun in 1948. All were 60 and older.
Researchers measured how often the participants exercised, and tracked them over a decade. During the study, 236 people developed dementia.
To see how physical activity might have affected dementia risk, the researchers broke the study population down into fifths that ranged from sedentary to highly active.
The one-fifth containing the most sedentary people were 50 percent more likely to develop dementia than the other four-fifths, the investigators found. In other words, even a little exercise helped.
The research team also compared physical activity to brain scans taken of about 2,000 study participants, and found a direct connection between exercise and brain size as people aged. Those who worked out had more total brain volume.
There are several theories why exercise might help brain health. Increased blood flow caused by physical activity might "beef up" the brain, increasing its volume and promoting the growth of additional neurons, said Dr. Malaz Boustani. He is research director of the Healthy Aging Brain Center at the Indiana University Center for Aging Research and a spokesman for the American Federation for Aging Research.
"Physical exercise might end up leading to increased density of the connections between the neurons and create alternative pathways for signals" that might otherwise be impeded due to age-related brain shrinkage, he added.
Boustani likened this process to a street system in a city. The more alternative routes are available to drivers, the less likely it is that a blockage on one street will lead to a city-wide traffic jam.
Exercise also promotes secretion of helpful brain chemicals such as brain-derived neurotrophic factor (BDNF). Tan explained that "BDNF actually encourages the growth of new neurons, and the preservation of those we already have."
Heather Snyder, senior director of medical and scientific operations for theAlzheimer's Association, said that the true answer is likely a combination of factors related to exercise.
"It's likely there are multiple benefits, and they all funnel together," Snyder said.
According to Boustani, these results support other studies that have shown an association between exercise and protection against dementia, but clinical trials aimed at proving a definite link have so far been disappointing.
"When we take it to the next step and start doing experiments, randomizing patients to physical exercise versus no physical exercise and see if that will protect their brain, the story becomes a little bit muddy and unclear," he said.
Regardless, Boustani said he prescribes moderate intensity physical exercise to his patients as one way to preserve their brain health -- 5,000 steps a day for about a month, increasing to 10,000 steps over time.
"Given that there's no harm, and there's a possible benefit to the brain that hasn't been fully explained, I work with my patients and their families to help improve their physical activity," he said.
The findings were published online recently in Journals of Gerontology: Medical Sciences.
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