A-A+

人老了还有这些想不到的好处

2015年11月15日 资讯 暂无评论 阅读 1,503 次
生日快乐蜡烛Image copyrightThinkstock

俗话说:“老有所乐,关键看你如何面对。”

欢迎来到老龄化社会。全世界60岁以上的老年人超过8亿,而百岁老人的数量甚至比冰岛的总人口还多(大约32.9万),这将对整个世界的经济和社会发展产生深远影响。从疾病缠身到皮肤松弛,再到思维变慢,老年人总是被各种各样的负面问题困扰不已。可是,在这团笼罩他们的乌云中,是否还能看到一线希望呢?

自古以来,年龄变老就是身体退化的同义词,但最近的研究表明,年龄变老绝不是简单的直线下滑。正如BBC Future之前的报道,人生的顶峰或许比你想象的来得晚。

老年从何时开始?

诗人但丁认为,人类45岁就开始步入老年。而调查显示,英国普通民众认为老年从59岁开始——受访者的年龄越老,他们眼中的老年开始得越晚。但联合国和多数科学家认为,60岁以后才能算老年。

感冒减少

随着年龄的增长,不仅大脑越来越聪明,免疫系统的记忆也越来越发达。人体的免疫系统每天还要面临数百万次的潜在危险,作为身体的警察,它必须学会如何识别危险。为此,人体生成了独特的白血球细胞来应对数以百万以分子形态存在的入侵者。当它们发现敌人时,就会形成“免疫记忆”。下一次再碰到这些敌人时,便可迅速集结应对。

免疫系统Image copyrightScience Photo Library
Image caption免疫系统能够记住以前的敌人,所以人老后就更容易抵抗感冒(图片来源:Science Photo Library)

昆士兰大学的约翰·阿珀姆(John Upham)表示,这种记忆可以保留很长时间。“如果有人患过多种流行病,他们的免疫系统有时甚至能记住四五十年前入侵身体的病毒。这种记忆的确会在七八十岁开始减弱,但却存在一个最佳时期——尤其是从四十多岁一直到七十岁左右——那时的免疫系统可以记住多年以来入侵身体的各种病毒。”

这种保护措施逐步积累之后,就会减少人们患病的几率。二十多岁的人可能每年会得两三次感冒,但到了五十多岁,平均每年只感冒一两次。

然而,其他的免疫能力却会随着年龄的增加而逐步减弱。人体新生成的白血球细胞会逐渐减少,活跃度也逐渐降低。老年人的免疫系统产生的抗体也在减少——这是一种用于鉴别并消灭病原体的蛋白质。但如果这能救人一命呢?

免疫增强

1918大流感是人类历史上最为致命的一次流行病爆发,当时约有5,000万人丧生。然而,在那次灾难中死亡最多的是20至40岁的人群,在人们的传统印象中,这恰恰是身体最强壮、最健康的一群人。2009年的猪流感爆发也出现了同样的离奇状况,死亡人数最多的年龄段都集中在65岁以下。

抗体Image copyrightScience Photo Library
Image caption老年人的免疫系统生成的抗体减少——但这可能是好事(图片来源:Science Photo Library)

研究人员认为,病毒导致受害者的免疫系统反应过度。免疫系统最活跃的人会产生最激烈但也最具破坏的反应,也就是所谓的“细胞因子风暴”。健康的免疫系统需要依靠积极的反馈——当发现病原体后,周围的组织会释放名为细胞因子的化学信息来求助。当细胞到达现场后,也会释放化学物质,从而吸引更多细胞前来支援。但有的时候,这种循环会失去控制,杀死健康的细胞,并引发致命炎症。目前还不清楚究竟是什么触发了这种风暴,但科学家通过持续研究制定了一种全新的治疗方案,把治疗对象从病毒本身转向了细胞因子风暴。

过敏减轻

对过敏的人来说,还有一条好消息。虽然医学界对过敏的最终成因仍然莫衷一是,但可以明确的是,这都是由抗体负责协调的。过敏的罪魁祸首就是免疫球蛋白E,与其他所有抗体一样,它的数量也会随着年龄的增长而减少。

威斯康星儿童医院的米歇尔·格雷森(Michell Grayson)表示,人的年龄越老,过敏症状就越轻。“过敏性疾病在儿童时期最严重,随后一直到青春期晚期都在减轻,一直延续到二十多岁。到了三十多岁再次出现,到了五六十岁,症状往往就会少得多。”

更聪明

很多民间谚语都会描述年龄的增长对大脑的破坏。然而,从很多至关重要的能力来看,老年人的大脑反而更加聪明。

过敏Image copyrightScience Photo Library
Image caption受到过敏困扰的人可以期待着晚年能够减轻症状(图片来源:Science Photo Library)

德国宾根大学的迈克尔·拉姆斯卡(Michael Ramscar)表示,我们对大脑的年龄存在误解。“人脑的神经元数量在出生后28周左右达到峰值,但有多达半数的神经元在青春期结束后死去。由于我们很少认为从出生到18岁期间会出现这种大幅变动,所以几乎可以肯定地说,用神经元的数量来衡量大脑尺寸并不能说明什么问题。”

“西雅图纵向研究”(Seattle Longitudinal Study)从1956年开始追踪6,000人的心智能力。这是迄今为止同类研究中历时最长的一项:所有的志愿者每过7年都会接受一次测试。虽然年龄较老的志愿者不太擅长数学,而且对命令的反应速度也会减慢,但他们在四五十岁时的词汇、空间、方向、言语记忆和问题解决能力却好于二十多岁时。

加州大学脑科学研究院的老年精神病学专家加里·斯冒(Gary Small)表示,这源自多年生活中积累的知识。“经过长达数年的练习后,人们能够更好地认清重要的事情,解决问题的能力也能得到改进。某种类型的知识将会逐年积累——我们称之为‘晶体智力’。”

这种状态是有生物学依据的。神经元末梢包裹着一种名为髓磷脂的脂质,可以隔绝神经信号。这是一种重要物质,它能加快电信号的传输速度。但人们普遍认为,随着年龄的增大,髓磷脂将会降解。其实并非如此。“随着人们年龄变老,你会发现这些末梢的绝缘性其实会加强,所以神经轴突在中年时的反应速度比年轻时更快。这些脑细胞的表现大概会在那段时期达到峰值。”斯冒说。

偏头痛Image copyrightScience Photo Library
Image caption研究显示,偏头痛可能会随着年龄的增大而减轻(图片来源:Science Photo Library)

性生活更和谐

有研究表明,老年人的性生活比你想象得更多、更和谐。在一项针对八十多岁的妇女进行的性生活调查中,研究人员发现半数受访者仍然能在“所有”或“多数”性生活中获得性高潮。其他研究也得出了类似的结论——有一项针对60岁以上的人群进行的调查发现,74%的男性和70%的女性的性满足感高于他们四十多岁时。伦敦两性关系治疗师塔拉·萨格里奥(Tara Saglio)认为,这是因为老年女性的不安全感有所降低。“老年女性对于表达自己的性欲更有信心。正是这种信心令她们获得了更和谐的性生活。”

偏头痛减轻

偏头痛同样会随着年龄的增大而减轻。瑞典科学家针对18岁及以上人群开展的一项研究显示,随着人们年龄的增大,偏头痛发作的时间会缩短,疼痛感和频率也会降低。在374名调查对象中,只有4人发展成了慢性头痛。

出汗减少

年龄增大后,人的汗腺会收缩,汗腺的数量也会减少。研究显示,二十多岁的人出汗量多于五十多岁或六十出头的人。

 

英文版本阅读:

“Growing old is great – when you consider the alternative,” as the saying goes.

Welcome to the age of ageing. With more than 800 million people over 60 and more centenarians than the population of Iceland (that’s about 329,000), the world is having to brace itself for the economic – and social – consequences. From a deluge of diseases to sagging skin and  the dulling of the senses, old age is beset with creeping failures, medical interventions, and low expectations. But can there be a silver lining for those joining the grey brigade?

Growing old has been synonymous with bodily decay since ancient times. The Greeks had a particularly dire view – many saw ageing itself as a disease. Yet the latest scientific research suggests ageing isn’t a straightforward decline after all. As BBC Future has reported before, life peaks later than you might think.

When does old age begin?

The poet Dante believed old age started at 45. A survey of the British public concluded that it starts at 59 – the older the respondent, the greater the number of years they considered old. But the United Nations and most scientists define it as any age after 60.

Fewer colds

It’s not just the brain that gets wiser with age. The human immune system encounters millions of potential dangers every day. As the body’s police force, it needs to learn to spot the dangers. For this, we produce unique white blood cells which are tailored to the molecular appearances of millions of different invaders. When they recognise a foe they stick around, forming an ‘immune memory’. The next time it turns up, they help to rally a rapid response.

John Upham from the University of Queensland says this memory can last a long time. “People who have gone through various epidemics, their immune systems can remember the virus for 40 or 50 years in some cases. It does begin to drop off in your 70s or 80s, but there’s a bit of a sweet spot for people – particularly from your 40s through to your late 60s and early 70s – where the immune system remembers the viruses experienced over the years.”

This cumulative protection translates into fewer colds. While 20-year olds can expect to catch two or three in a year, over 50s average only one or two.

Other immune defences however, tend to weaken with age. The body produces fewer new white blood cells, and they become sluggish. Aged immune systems also produce less antibodies – proteins which stick to pathogens to help identify and eliminate them. But what if this could be life-saving?

Outliving outbreaks

The 1918 flu pandemic was the deadliest in human history, killing 50 million people. But it was most lethal for those usually thought of as fit and strong, aged from 20 to 40. The 2009 swine flu outbreak followed the same bizarre pattern, with most fatalities in those under the age of 65.

It’s thought that the viruses caused their victims’ immune systems to overreact. Those with the most vigorous immune systems launched the most dramatic, and damaging, responses, in what’s known as a ‘cytokine storm’. A healthy immune response relies on positive feedback – when a pathogen is found, the surrounding tissues release chemical messages, called cytokines, asking for help. As cells arrive on site, they are encouraged to release the chemicals too, encouraging even more cells to arrive. But sometimes the loop gets out of control, killing healthy cells and leading to potentially fatal inflammation. It’s not yet known what triggers the storms, but ongoing research has inspired a new treatment for the flu which acts on the cytokine storm instead of the virus itself.

Declining allergies

And there’s good news for those with allergies, too. While the ultimate causes of allergies are still hotly debated, all are mediated by antibodies. The main culprit is Immunoglobulin E and like all other antibodies, its production diminishes with age.

Mitchell Grayson from the Children’s Hospital of Wisconsin says the older you get, the less severe the symptoms are likely to be. “Allergic disease peaks in childhood and then seems to decrease throughout late adolescence and into their 20s. In the 30s there is another resurgence until people get into their 50s and 60s when the symptoms tend to get less common.”

Cleverer

There’s no shortage of slang terms to describe the destructive effects of ageing on the brain. Yet in a number of vitally important abilities, older brains  actually turn out to be smarter.

Michael Ramscar from Tubingen University says we have misunderstood how the brain ages. “The number of neurons in the human brain peaks at around 28 weeks after birth, but as many as half of the neurons produced die by the end of adolescence. Since we don’t usually think of the period from birth to age 18 as one of hideous decline, it seems safe to conclude that brain size as measured in neuronal numbers is not much of an indicator of anything.”

The Seattle Longitudinal Study has followed the mental abilities of 6,000 people since 1956. It’s the longest-running study of its kind, with the same volunteers tested every seven years. While older volunteers aren’t as good at maths and are slower to respond to commands, for vocabulary, spatial orientation, verbal memory, and problem solving abilities, they were better in their late 40s and 50s than they were in their 20s.

Several studies have shown that older people have more – and better – sex than you might think

Gary Small, who studies geriatric psychiatry at the University of California Brain Research Institute, says it’s down to the knowledge accumulated thanks to all those extra years. “People develop a greater perspective of what’s important, the ability to problem-solve is streamlined after years of practice. And there’s accumulation of certain types of knowledge – what’s called crystallised intelligence.”

It’s a pattern underpinned by biology. Nerve signals are insulated by a fatty material, myelin, which envelops the wiry ends of neurons. It’s important stuff, increasing the speed  electrical signals are transmitted, but it was thought to deteriorate as people got older. Not so. “As people age you find that the insulation around these long wires is actually increased, so axons fire more quickly in middle-aged people than in younger people. There’s a peak performance of these brain cells around that time,” Small says.

Better sex

Several studies have shown that older people have more – and better – sex than you might think. A study of the sexual activity and satisfaction of women in their 80s found that half still had orgasms ‘always’ or ‘most of the time’ during sex. Other studies have reached similarly striking conclusions – a survey of people over the age of 60 found that 74% of men and 70% of women reported a greater sexual satisfactionthan when they were in their 40s. Tara Saglio, a relationship therapist based in London, puts this down to older women having fewer insecurities. “Older women are more confident about expressing their own sexuality. It’s that confidence that makes sex better.”

Fewer migraines

Migraines can become less of a headache as we age, too. ASwedish study of patients 18 and older found that attacks become shorter, less painful and less frequent as people get older. Of 374 people enrolled in the study, only four developed chronic headaches.

Less sweaty

Sweat glands shrink and become less numerous as people get older. Research shows that those in their 20s can expect to sweat more than those on their 50s and early 60s.

Cheating death

Still not convinced? Even at advanced years, the Grim Reaper need not be as close as you might expect. The oldest old are healthier than ever before and still have a good chance of celebrating a few more birthdays. In 2011-2014, the average 25-year-old had a life expectancy of 84 (women) or 80 (men), while a 95 year-old could expect to see their 98th (women) or 97th (men) birthday. Even at 80, women have a 95% chance of living another year.

标签:

给我留言