The benefits, and the costs, of living longer

    IT IS written in the Bible's Book of Genesis that Methuselah lived to be 969. He held the record, but there seem to have been plenty of other multicentenarians around at the time, including Noah and old Adam himself. Their ages are not to be taken literally. In another part of Genesis, man's lifespan is put at a mere 120 years. The person with the longest documented life in modern times, Jeanne Calment, reached 122, but no one else has come close.

    In most of recorded history even the more familiar three score years and ten was rare. Angus Maddison, an economic historian, has estimated that life expectancy during the first millennium AD averaged about 25 years （which in practice meant that lots of children died very young and many of the rest survived to middle age）. The big turnaround came with the industrial revolution, mainly because many more children survived into adulthood, thanks to better sanitation, more control over epidemics, improved nutrition and higher living standards.

    By the beginning of the 20th century average life expectancy in America and the better-off parts of Europe was close to 50, and kept on rising. By mid-century the gains from lower child mortality had mainly run their course. The extra years were coming from higher survival rates among older people. The UN thinks that life expectancy at birth worldwide will go up from 68 years at present to 76 by 2050 and in rich countries from 77 to 83. （These are averages for both sexes; women generally live five or six years longer than men, for reasons yet to be fathomed）. Most experts now agree that there will be further rises, but disagree about their extent.

    Things fall apart

    Some of them argue that the human lifespan is finite because bodies, in effect, wear out; that most of the easy gains have been made; and that the rate of increase is bound to slow down because people now die mostly of chronic diseases-cancer, heart problems, diabetes-which are harder to fix. They also point to newer health threats, such as HIV/AIDS, SARS, bird flu and swine flu, as well as rising obesity in rich countries-to say nothing of the possibility of fresh pandemics, social and political unrest and natural disasters.

    Nearly 30 years ago James Fries at Stanford University School of Medicine put a ceiling of 85 years on the average potential human life span. More recently a team led by Jay Olshansky at the University of Illinois at Chicago said it would remain stuck there unless the ageing process itself can be brought under control. Because infant mortality in rich countries is already low, they argued, further increases in overall life expectancy will require much larger reductions in mortality at older ages. In Mr Olshansky's view, none of the life-prolonging techniques available today-be they lifestyle changes, medication, surgery or genetic engineering-will cut older people's mortality by enough to replicate the gains in life expectancy achieved in the 20th century.

    Blessing or curse?祝福还是诅咒？

    That may sound reasonable, but the evidence points the other way. Jim Oeppen at Cambridge University and James Vaupel at the Max Planck Institute for Demographic Research in Rostock have charted life expectancy since 1840, joining up the figures for whatever country was holding the longevity record at the time, and found that the resulting trend line has been moving relentlessly upward by about three months a year. They think that by 2050 average life expectancy in the best-performing country could easily reach the mid-90s.

    Rises in life expectancy have been habitually underestimated because it seemed unlikely that the improvement could go on for ever, and just as regularly the figures have had to be revised soon afterwards. Some experts now think there may be no theoretical limit at all, pointing to the huge rise in the number of centenarians in the past few decades. In America they are the fastest-growing section of the population, with an increase from 3,700 in 1940 to over 100,000 now.

    Why are people living ever longer? Robert Fogel at the University of Chicago, a Nobel prize-winner in economics, reckons that improved medical care and technology are only part of the answer. Another part, he thinks, is something he has dubbed "technophysio evolution". Over the past few centuries humans have developed more resilient physiques because they gained unprecedented control over their environment and their living conditions. Western people's average body size has increased by 50% over the past 250 years. Larger body size （but not obesity）, Mr Fogel's research has shown, is associated with better health and longer life.

    But modern life has its downsides too. Stress is often seen as a life-shortening factor-though perhaps the effects are not as lethal as some people think, or else the Japanese, who are famous for working long hours, would not have the highest life expectancy in the world.

    Another hazard of affluence is getting fat. Around 10-20% of the adult population in many rich countries, and over 30% in America, are now clinically obese. Overweight people are at greater risk of cardiovascular and respiratory diseases, cancer, type-II diabetes and other life-shortening ailments-though it is not yet clear whether the effects are strong enough to cancel the trend to greater longevity.

    And life expectancy can go down as well as up. In much of eastern Europe it started dropping in the 1980s in response to the upheaval in the region, and despite a subsequent slight recovery it has still not regained the level of the 1960s.

    People almost everywhere could extend their life spans further just by doing a few sensible things, such as not smoking, drinking only in moderation, eating lots of fruit and vegetables and taking regular exercise. Educated folk are better at keeping to such rules, and as a group they live markedly longer than those with only basic schooling. Richer people, unfairly, also live longer than less well-off ones, even in the developed world.

    But all this is tinkering at the edges. Mankind's dream has been to conquer ageing altogether, and scientists are working on it. Spare-part surgery to replace worn-out bits of the anatomy is already well-established and will get better with the use of stem-cell technology. For a more general effect, experiments on rodents have shown that a severely restricted but balanced diet can increase their lifespan by about 30%. But nobody knows whether this would work in humans, and even if it did, there might be few takers.

    The longer-term hope is to find a way of switching off the ageing process by manipulating the appropriate genes, which in theory could make people near-immortal （though they could still die of accidents and diseases）. But if that were feasible, the consequences would need to be carefully thought through. In Jonathan Swift's "Gulliver's Travels", the hero meets a tribe of immortals, the Struldbruggs, who far from being wise and serene turn out to be a miserable lot: "Whenever they see a funeral, they lament and repine that others have gone to a harbour of rest to which they themselves never can hope to arrive."

    Hale and hearty

    People in the rich world can now expect to live, on average, more than a quarter of a century longer than they did 100 years ago. Is that a blessing or a Struldbruggian curse? Clearly it depends on whether they become old and frail at the same age as before and just limp on for much longer, or if the extra years are hale and hearty ones.

    Most of the evidence supports the more cheerful view. Research led by Kenneth Manton at Duke University found that in recent years disability above the age of 65 in America has been falling significantly. In other rich countries the picture is more mixed. When the OECD recently looked at 12 member countries, it found clear signs of a recent decline in disability in elderly people in only five of them （including America）. But other studies produced more optimistic results.

    By and large, people do now seem to remain in good shape for longer. Moreover, the period of ill health that usually precedes the final goodbye has got shorter in the past few decades, which demographers call "compression of morbidity" （as a rule of thumb, the bulk of spending on an individual's health care is concentrated in the last year or two of life, and particularly in the final six months）. This compression has a variety of causes, including the shift from manual to physically less demanding white-collar work, rising levels of education and much-improved health care and medical technology, from keyhole surgery to heart pacemakers. Eighty, it is said, is the new 65.

    But even fairly fit older people need more health care than younger ones, not least because they often suffer from chronic diseases that are expensive to treat. In the EU, one estimate puts health-care spending on the elderly at about 30-40% of total health spending. So will the better health of an ageing population, good as it has been for so many, impose unaffordable costs on public-health budgets?

    Over the past few decades all OECD countries have seen their health spending grow considerably faster than their economies. Ageing populations will add further momentum to that growth. Howard Oxley, a health-care expert at the OECD, reckons that increased spending on health and long-term care for the elderly could amount to an extra three-and-a-half percentage points of rich countries' GDP by the middle of the century-and a lot more if spending on medical technology continues to go up at current rates.

    Measured by spending on health care as a share of GDP, America already tops the list, shelling out the equivalent of more than 15% of GDP （see chart 4）. The American government's health-care spending will be hugely affected by ageing because of Medicare, the state-funded health-care programme for the elderly and disabled, and Medicaid, the programme for the poor （and often also old, because it covers long-term care）.

    President Barack Obama is determined to reform his country's health-care system to improve coverage and, eventually, drive down costs. More money does not always produce better results. People in America are less healthy and die sooner than in Britain, which proportionately spends little more than half as much on its health care. According to David Cutler, an economics professor at Harvard who has advised the president on the reform, even doctors believe that around 30% of money spent on health care in America is wasted.

    Peter Orszag, head of the Office of Management and Budget, has recently been praising the work of a group of medical experts at Dartmouth Medical School, led by Elliott Fisher, which has been compiling an atlas of regional variations in American medical practice and health-care spending, mainly for people on the Medicare programme. It found that in 2006 Medicare spending varied more than threefold across American hospital referral regions. Again, higher spending does not seem to result in better care or greater patient satisfaction. Because the system has encouraged the provision of lots of doctors, specialists, hospitals and expensive diagnostic kit, all of them are kept busy without much regard to results.

    The trouble with health care in America, says Muriel Gillick, a geriatrics expert at Harvard Medical School, is that people want to believe that "there is always a fix." She argues that the way Medicare is organised encourages too many interventions towards the end of life that may extend the patient's lifespan only slightly, if at all, and can cause unnecessary suffering. It would often be better, she thinks, not to try so hard to eke out a few more hours or weeks but to concentrate on quality of life.

    Take care

    But long before they get to that point, growing numbers of old people will become less able to look after themselves and need more care. Across the OECD, spending on long-term care is already equivalent to around 15% of total health spending and is rising fast. The great bulk of that care-an estimated 80%-is still provided by family and friends, the traditional source of support for the elderly. But more women are going out to work, so fewer of them have time to look after old folk and formal help is becoming increasingly important.

    In most developed countries only a small minority of over-65s-between 3% and 6%-live in institutions. Keeping old people in nursing homes or hospitals is expensive, staff is hard to find, and in any case most people would much rather be looked after at home. Many countries are now providing grants to adapt homes, paying families for the care they provide and supplying helpers to give a hand with things like dressing and bathing.

    With far more people reaching a great age, a lot more such care will be needed in future. How will it be paid for? A few far-sighted countries-including Germany, the Netherlands, Luxembourg and Japan-have already introduced mandatory long-term-care insurance schemes. Others may have to follow.

    圣经的创世纪中写到玛土撒拉活了969岁。他一直保持着这一长寿记录，不过那时似乎有许多几百岁的老人，诺亚和老亚当自己也在其中。当然没人会把这些当真。在创世纪的另一部分，人类的寿命仅为120岁。现代有记录的最长寿命者是Jeanne Calment,他活到了122岁，此外无人能与他匹敌。

    在绝大多数历史记载中，就连较为常见的古稀老人都很少。经济史专家Angus Maddison估计，公元后一千年的时间里，人类的平均寿命约为25岁（实际上，这意味着许多儿童年幼夭折，而剩余的则活到中年）.这种情况在工业革命后发生了巨大转变，主要由于更多儿童能够长大成人，这要归功于良好的卫生状况、对传染病的控制、人们的营养状况改善以及生活水准提高。

    20世纪开始时，美国和欧洲比较富裕地区的平均寿命已经接近50岁。到20世纪中期，平均寿命的增长得益于儿童死亡率一直保持在较低的水平；此后则缘于初老期死亡率的降低。联合国预计，在全球范围内，出生时的平均预期寿命将从现在的68岁上升到2050年的76岁；在富裕国家，则将从77岁上升到 83岁。（这些数字包括男女在内；一般女性总是比男性多活五到六年，原因还不得而知。）现在的多数专家同意人类平均寿命会继续增加，但对增加多少却有不同看法。

    全面破解长寿之因

    一些专家认为人类寿命有限是因为人体本身渐渐衰弱；使人类长寿的条件中容易达成的多数都已经达成；平均寿命增加的速度必然会放慢，因为如今人们多死于难以根治的慢性疾病，如癌症，心脏病，糖尿病。专家也提及新型健康杀手，诸如艾滋病，非典，禽流感，猪流感以及富裕国家日渐增多的肥胖症患者，更别提还有发生新型流行病、社会及政治不安定、自然灾害的可能了。

    约30年前，斯坦福大学医学院的James Fries把人类平均寿命的可能上限定为85岁。最近芝加哥伊利诺伊大学Jay Olshansky领导的一个小组称，除非衰老的过程本身能得到控制，否则平均寿命的上限将停滞不前。他们认为，富裕国家的婴儿死亡率已经很低，要想进一步增加总体平均寿命，就要大大降低初老期的死亡率。在Olshansky先生看来，目前没有一种延长寿命的技术--无论是改变生活方式，药物，手术还是基因工程--能大量减少初老期老人的死亡率，做到象20世纪那样大幅提高平均寿命。

    Blessing or curse?祝福还是诅咒？

    他们的观点听上去颇为合理，但事实却与此相反。剑桥大学的Jim Oeppen和马克斯？普朗克人口研究所（位于德国的罗斯托克）的James Vaupel把1840年以来的平均寿命制成图表，加入每个时期的长寿记录，无论保持这一纪录的是哪个国家。他们发现得出的趋势线持续每年上移3个月。他们预计，到2050年，表现最好的国家平均寿命能轻易达到95岁左右。

    平均寿命的增加总是习惯性地被低估，因为这种增加似乎不可能无止境地延伸下去，而这些数据也应该定期及时修正。一些专家现在认为也许平均寿命根本没有理论上的限制，他们指出过去几十年中百岁老人的数量大大增加。美国百岁老人是人口结构中增长最快的一部分，人数从1940年的3700人激增至现在的十万人。

    为什么人类活得更长了？诺贝尔经济学奖得主、芝加哥大学的Robert Fogel觉得医疗保健的改善和科技发达只是部分答案。他把另一部分原因称为"技术性体格进化".过去几个世纪，由于人类对环境和生活条件获得了前所未有的控制力，人体的适应性增强。西方人的平均体型在过去250年增加了50%.Fogel的调查显示，更大的体型（并非肥胖）与良好的健康、更长的寿命都有关系。

    但现代生活也有其消极的一面。压力通常被视为缩短寿命的因素--尽管这种影响也许不像大家想象的那样致命，否则以工作时间长而闻名的日本人就不会有世界上最长的平均寿命了。

    另一个有害的影响则是变胖。许多富裕国家中大约10-20%的成年人，美国则是30%以上，都患有肥胖症。超重者罹患心血管、呼吸道疾病，癌症，二型糖尿病和其他缩短寿命的疾病的风险都大为增加，尽管还不清楚其负面影响是否大到抵消使其长寿的正面影响。

    而且平均寿命不仅可能增加，也可能会减少。20世纪八十年代，在东欧许多地区，这一数字因该地区的剧变开始下降，尽管随后又略有回升，但仍未恢复20世纪60年代的水平。

    几乎全世界的人都能通过一些合理行为延长生命，包括不抽烟，适度饮酒，多吃水果和蔬菜，定期运动。受过良好教育的人往往能更好地遵守这些规则，因而他们作为一个群体远比只受过基础教育的人长寿。不公平的是，较为富有的人也比那些境遇不佳的人活得更久，特别是在发达国家。

    但所有这些都只是小修小补。人类的梦想是从根本上征服衰老，科学家正孜孜以求。以手术替换人体衰竭的器官已是成熟的技术，并且还将随干细胞技术的引入更上一层楼。对小白鼠的实验显示，受到严格限制的均衡饮食能将寿命提高30%左右。但没人知道这对人类是否有效，即使有效，大概这么做的人也不会多。

    人类的远期期望是通过操纵正确的基因，找到终止衰老的方式，从理论上来说，这会使人类近乎永生（尽管他们仍可能死于意外或疾病）.但如果这真的可行，我们必须仔细斟酌其后果。在乔纳森？斯威夫特的格列佛游记中，主人公遇到一个不死人部落"斯特鲁布鲁格",他们远非智慧安宁，是个悲惨的群体："每逢葬礼，他们便哀叹抱怨，自己永远无法象他人那样进入安息之所。"

    老当益壮

    富裕国度的人们如今可以指望他们的平均寿命比100年前长25年。这是福祉还是"斯特鲁布鲁格"式的诅咒？显然，这要看他们是和以前一样，在同一年龄变得年老体衰，只是苟延残喘更长时间，还是老当益壮地度过延长的寿命。

    多数证据支持更令人鼓舞的那种看法。由杜克大学的Kenneth Manton主持的研究发现，近几年，美国65岁以上行为能力丧失的老人人数大为减少。在其他富裕国家，情况则更为复杂。最近经合组织对其12个成员国进行调查，发现其中5个国家（包括美国）丧失行为能力的老人明显减少。但其他研究却显示更为乐观的结果。

    总体看来，现代人似乎能更长时间保持身体健康。此外，告别人世前的患病时间在过去几十年中也有所缩短，人口学家称之为"病态期压缩"（根据经验，个人医疗保健的支出的大头都集中在生命的最后一、二年，特别是最后半年。）造成这种压缩的原因多样，包括从体力劳动转向物理强度不大的白领工作；教育程度提高；医疗保健大为改善，从关键手术到心脏起搏器各方面医学技术都大大提高。据说，现在，80岁就是新的65岁。

    但即使是身体状况相当好的老年人也比年轻人更需要医疗保健，这特别是因为他们通常受慢性病折磨，而慢性病治疗费用昂贵。欧盟的一个预计显示，用于老年人的医保支出占了整个医保支出的30-40%.尽管老龄化人口更为良好的健康状况对许多人都有好处，但这是否会给公共健康预算带来无法负担的负担？

    过去几十年中，所有经合组织国家的健康支出远比它们的经济增长更快。老龄化人口则会进一步推动这种趋势。经合组织的卫生保健专家Howard Oxley推测，在老年人健康和对他们长期照顾方面所增加的支出，到本世纪中期，将达到富有国家GDP的 3.5%;而且这种支出还会大为增加--如果用于发展医疗技术的费用以现有速度继续增加的话。

    如果根据医保占GDP的比例来衡量，那美国高居榜首，它这方面的支出相当于其GDP的15%（见图4）.由于其老年医疗保健制度、国家出资的老年人和残疾人医保项目、针对穷人的公共医疗补助制度（通常也针对老人，因为这一制度覆盖较长时期）,老龄化将严重影响美国政府的医保支出。

    总统巴拉克？奥巴马决心改革美国的医疗保健系统，以达到提高覆盖面、最终降低成本的目的。更多投入并非总能产生更好的结果。美国人不如英国人健康也不如他们活得长，而按比例算，英国人的医保支出只相当于美国人的一半略多。据哈佛大学的经济学教授David Cutler说，就连医生也认为美国约30%用于医保的钱是浪费掉的。Cutler教授曾就医保改革向总统提出建议。

    行政管理和预算局局长Peter Orszag最近频频表扬达特茅斯医学院以Elliott Fisher为首的一群医学专家，他们一直在编辑一张地图，以反映美国医疗实践以及医保支出的地区性差异，而医保支出主要用于老年医疗保健制度。他们发现，在美国有推荐医院的地区，2006年老年医疗保健制度的支出翻了3倍。因为该制度鼓励提供更多医生、专家、医院、价值不菲的诊断器械，但所有这些资源都徒劳无益地处于忙碌状态。这再次说明更高的支出未必意味着对病人更好的照顾和更高的病人满意度。

    哈佛医学院老年病学专家Muriel Gillick说，美国医疗保健的症结在于人们想要相信"总有治疗之道。"她指出老年医疗保健制度鼓励过度干预老人的临终生活，就算这能延长病人的生命，也极为有限，而同时却使病人承受不必要的痛苦。她认为很多情况下，竭尽全力使病人多活区区几小时或几周不如将精力花在提高他们的生活质量上。

    照顾老人

    但远在走到生命终点之前，就有日益增多的老人渐渐无法照顾自己，需要更多关爱。纵观全部经合组织成员国，花费在老人长期护理上的费用已经相当于整个健康支出的15%,而且还在迅速增加。这种护理大部分（约80%）仍由照顾老人的传统力量--家庭和朋友提供。但越来越多妇女外出工作，她们很少有人有空照料老人，因此官方帮助正变得越来越重要。

    在多数发达国家只有少量65岁以上的人（3%到6%）生活在各老人疗养机构。让老年人住疗养院或医院费用昂贵，护理员工难找；而且，任何情况下，多数人都更愿意在家接受照顾。目前许多国家为改建私房提供补助（使之更方便老人居住）,资助照顾老人的家庭，在为老人穿衣、洗澡等日常事务上提供帮手。

    随大量人口步入老龄，他们今后会需要更多照顾。谁会为此买单？几个眼光长远的国家，包括德国、荷兰、卢森堡和日本，都已经引入长期护理强制保险计划。其他国家也应步其后尘。