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?祝福還是詛咒？

    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.

    圣經的創世紀中寫到瑪土撒拉活了969歲。他一直保持著這一長壽記錄，不過那時似乎有許多幾百歲的老人，諾亞和老亞當自己也在其中。當然沒人會把這些當真。在創世紀的另一部分，人類的壽命僅為120歲。現代有記錄的最長壽命者是Jeanne Calment,他活到了122歲，此外無人能與他匹敵。

    在絕大多數歷史記載中，就連較為常見的古稀老人都很少。經濟史專家Angus Maddison估計，公元后一千年的時間里，人類的平均壽命約為25歲（實際上，這意味著許多兒童年幼夭折，而剩余的則活到中年）.這種情況在工業革命后發生了巨大轉變，主要由于更多兒童能夠長大成人，這要歸功于良好的衛生狀況、對傳染病的控制、人們的營養狀況改善以及生活水準提高。

    20世紀開始時，美國和歐洲比較富裕地區的平均壽命已經接近50歲。到20世紀中期，平均壽命的增長得益于兒童死亡率一直保持在較低的水平；此后則緣于初老期死亡率的降低。聯合國預計，在全球范圍內，出生時的平均預期壽命將從現在的68歲上升到2050年的76歲；在富裕國家，則將從77歲上升到 83歲。（這些數字包括男女在內；一般女性總是比男性多活五到六年，原因還不得而知。）現在的多數專家同意人類平均壽命會繼續增加，但對增加多少卻有不同看法。

    全面破解長壽之因

    一些專家認為人類壽命有限是因為人體本身漸漸衰弱；使人類長壽的條件中容易達成的多數都已經達成；平均壽命增加的速度必然會放慢，因為如今人們多死于難以根治的慢性疾病，如癌癥，心臟病，糖尿病。專家也提及新型健康殺手，諸如艾滋病，非典，禽流感，豬流感以及富裕國家日漸增多的肥胖癥患者，更別提還有發生新型流行病、社會及政治不安定、自然災害的可能了。

    約30年前，斯坦福大學醫學院的James Fries把人類平均壽命的可能上限定為85歲。最近芝加哥伊利諾伊大學Jay Olshansky領導的一個小組稱，除非衰老的過程本身能得到控制，否則平均壽命的上限將停滯不前。他們認為，富裕國家的嬰兒死亡率已經很低，要想進一步增加總體平均壽命，就要大大降低初老期的死亡率。在Olshansky先生看來，目前沒有一種延長壽命的技術--無論是改變生活方式，藥物，手術還是基因工程--能大量減少初老期老人的死亡率，做到象20世紀那樣大幅提高平均壽命。

    Blessing or curse?祝福還是詛咒？

    他們的觀點聽上去頗為合理，但事實卻與此相反。劍橋大學的Jim Oeppen和馬克斯？普朗克人口研究所（位于德國的羅斯托克）的James Vaupel把1840年以來的平均壽命制成圖表，加入每個時期的長壽記錄，無論保持這一紀錄的是哪個國家。他們發現得出的趨勢線持續每年上移3個月。他們預計，到2050年，表現最好的國家平均壽命能輕易達到95歲左右。

    平均壽命的增加總是習慣性地被低估，因為這種增加似乎不可能無止境地延伸下去，而這些數據也應該定期及時修正。一些專家現在認為也許平均壽命根本沒有理論上的限制，他們指出過去幾十年中百歲老人的數量大大增加。美國百歲老人是人口結構中增長最快的一部分，人數從1940年的3700人激增至現在的十萬人。

    為什么人類活得更長了？諾貝爾經濟學獎得主、芝加哥大學的Robert Fogel覺得醫療保健的改善和科技發達只是部分答案。他把另一部分原因稱為"技術性體格進化".過去幾個世紀，由于人類對環境和生活條件獲得了前所未有的控制力，人體的適應性增強。西方人的平均體型在過去250年增加了50%.Fogel的調查顯示，更大的體型（并非肥胖）與良好的健康、更長的壽命都有關系。

    但現代生活也有其消極的一面。壓力通常被視為縮短壽命的因素--盡管這種影響也許不像大家想象的那樣致命，否則以工作時間長而聞名的日本人就不會有世界上最長的平均壽命了。

    另一個有害的影響則是變胖。許多富裕國家中大約10-20%的成年人，美國則是30%以上，都患有肥胖癥。超重者罹患心血管、呼吸道疾病，癌癥，二型糖尿病和其他縮短壽命的疾病的風險都大為增加，盡管還不清楚其負面影響是否大到抵消使其長壽的正面影響。

    而且平均壽命不僅可能增加，也可能會減少。20世紀八十年代，在東歐許多地區，這一數字因該地區的劇變開始下降，盡管隨后又略有回升，但仍未恢復20世紀60年代的水平。

    幾乎全世界的人都能通過一些合理行為延長生命，包括不抽煙，適度飲酒，多吃水果和蔬菜，定期運動。受過良好教育的人往往能更好地遵守這些規則，因而他們作為一個群體遠比只受過基礎教育的人長壽。不公平的是，較為富有的人也比那些境遇不佳的人活得更久，特別是在發達國家。

    但所有這些都只是小修小補。人類的夢想是從根本上征服衰老，科學家正孜孜以求。以手術替換人體衰竭的器官已是成熟的技術，并且還將隨干細胞技術的引入更上一層樓。對小白鼠的實驗顯示，受到嚴格限制的均衡飲食能將壽命提高30%左右。但沒人知道這對人類是否有效，即使有效，大概這么做的人也不會多。

    人類的遠期期望是通過操縱正確的基因，找到終止衰老的方式，從理論上來說，這會使人類近乎永生（盡管他們仍可能死于意外或疾病）.但如果這真的可行，我們必須仔細斟酌其后果。在喬納森？斯威夫特的格列佛游記中，主人公遇到一個不死人部落"斯特魯布魯格",他們遠非智慧安寧，是個悲慘的群體："每逢葬禮，他們便哀嘆抱怨，自己永遠無法象他人那樣進入安息之所。"

    老當益壯

    富裕國度的人們如今可以指望他們的平均壽命比100年前長25年。這是福祉還是"斯特魯布魯格"式的詛咒？顯然，這要看他們是和以前一樣，在同一年齡變得年老體衰，只是茍延殘喘更長時間，還是老當益壯地度過延長的壽命。

    多數證據支持更令人鼓舞的那種看法。由杜克大學的Kenneth Manton主持的研究發現，近幾年，美國65歲以上行為能力喪失的老人人數大為減少。在其他富裕國家，情況則更為復雜。最近經合組織對其12個成員國進行調查，發現其中5個國家（包括美國）喪失行為能力的老人明顯減少。但其他研究卻顯示更為樂觀的結果。

    總體看來，現代人似乎能更長時間保持身體健康。此外，告別人世前的患病時間在過去幾十年中也有所縮短，人口學家稱之為"病態期壓縮"（根據經驗，個人醫療保健的支出的大頭都集中在生命的最后一、二年，特別是最后半年。）造成這種壓縮的原因多樣，包括從體力勞動轉向物理強度不大的白領工作；教育程度提高；醫療保健大為改善，從關鍵手術到心臟起搏器各方面醫學技術都大大提高。據說，現在，80歲就是新的65歲。

    但即使是身體狀況相當好的老年人也比年輕人更需要醫療保健，這特別是因為他們通常受慢性病折磨，而慢性病治療費用昂貴。歐盟的一個預計顯示，用于老年人的醫保支出占了整個醫保支出的30-40%.盡管老齡化人口更為良好的健康狀況對許多人都有好處，但這是否會給公共健康預算帶來無法負擔的負擔？

    過去幾十年中，所有經合組織國家的健康支出遠比它們的經濟增長更快。老齡化人口則會進一步推動這種趨勢。經合組織的衛生保健專家Howard Oxley推測，在老年人健康和對他們長期照顧方面所增加的支出，到本世紀中期，將達到富有國家GDP的 3.5%;而且這種支出還會大為增加--如果用于發展醫療技術的費用以現有速度繼續增加的話。

    如果根據醫保占GDP的比例來衡量，那美國高居榜首，它這方面的支出相當于其GDP的15%（見圖4）.由于其老年醫療保健制度、國家出資的老年人和殘疾人醫保項目、針對窮人的公共醫療補助制度（通常也針對老人，因為這一制度覆蓋較長時期）,老齡化將嚴重影響美國政府的醫保支出。

    總統巴拉克？奧巴馬決心改革美國的醫療保健系統，以達到提高覆蓋面、最終降低成本的目的。更多投入并非總能產生更好的結果。美國人不如英國人健康也不如他們活得長，而按比例算，英國人的醫保支出只相當于美國人的一半略多。據哈佛大學的經濟學教授David Cutler說，就連醫生也認為美國約30%用于醫保的錢是浪費掉的。Cutler教授曾就醫保改革向總統提出建議。

    行政管理和預算局局長Peter Orszag最近頻頻表揚達特茅斯醫學院以Elliott Fisher為首的一群醫學專家，他們一直在編輯一張地圖，以反映美國醫療實踐以及醫保支出的地區性差異，而醫保支出主要用于老年醫療保健制度。他們發現，在美國有推薦醫院的地區，2006年老年醫療保健制度的支出翻了3倍。因為該制度鼓勵提供更多醫生、專家、醫院、價值不菲的診斷器械，但所有這些資源都徒勞無益地處于忙碌狀態。這再次說明更高的支出未必意味著對病人更好的照顧和更高的病人滿意度。

    哈佛醫學院老年病學專家Muriel Gillick說，美國醫療保健的癥結在于人們想要相信"總有治療之道。"她指出老年醫療保健制度鼓勵過度干預老人的臨終生活，就算這能延長病人的生命，也極為有限，而同時卻使病人承受不必要的痛苦。她認為很多情況下，竭盡全力使病人多活區區幾小時或幾周不如將精力花在提高他們的生活質量上。

    照顧老人

    但遠在走到生命終點之前，就有日益增多的老人漸漸無法照顧自己，需要更多關愛。縱觀全部經合組織成員國，花費在老人長期護理上的費用已經相當于整個健康支出的15%,而且還在迅速增加。這種護理大部分（約80%）仍由照顧老人的傳統力量--家庭和朋友提供。但越來越多婦女外出工作，她們很少有人有空照料老人，因此官方幫助正變得越來越重要。

    在多數發達國家只有少量65歲以上的人（3%到6%）生活在各老人療養機構。讓老年人住療養院或醫院費用昂貴，護理員工難找；而且，任何情況下，多數人都更愿意在家接受照顧。目前許多國家為改建私房提供補助（使之更方便老人居住）,資助照顧老人的家庭，在為老人穿衣、洗澡等日常事務上提供幫手。

    隨大量人口步入老齡，他們今后會需要更多照顧。誰會為此買單？幾個眼光長遠的國家，包括德國、荷蘭、盧森堡和日本，都已經引入長期護理強制保險計劃。其他國家也應步其后塵。