長壽的高昂代價

長壽的高昂代價

人類究竟能活多久？這樣一個老掉牙的問題卻在近幾年成了各國政府新的挑戰(zhàn)。為了讓每個人都能有尊嚴地度過人生的最后時光，我們要為長壽付出高昂的代價。

測試中可能遇到的詞匯和知識：

strain拉緊；竭力[stre?n]

pricey昂貴的['pra?si]

advent出現(xiàn)，到來['ædvent]

impetus動力，推動力['?mp?t?s]

backdrop背景幕，背景['bækdr?p]

actuary保險精算師['ækt?u?ri]

underlying基本的，隱含的[??nd?'la???]

successive接連的，連續(xù)的[s?k'ses?v]

club集合 [kl?b]

annuity年金，養(yǎng)老金[?'nju??ti]

unwittingly不知不覺地，無意地[?n'w?t??li]

render提供，實施['rend?(r)]

How long can humans live? It's a pricey question（769 words）

By Norma Cohen

How long can human beings live, anyway? It is — no pun intended — an age-old question. But the answer has posed acute challenges for governments in recent years. Sharp extensions in longevity are straining social safety nets that were created to allow the old and frail to live their last days in dignity. The probable length of human life comes with a very specific price tag.

It was not ever thus. In the early years following the Enlightenment in the 17th century, people asked why we no longer live to the age of the sages as described in the Bible, according to David Boyd Haycock, a professor of medical history at Oxford university. Adam, after all, lived to be 930 while Methuselah topped him at 939 years. Only the advent of mortality tables in the 18th century limited the debate.

The question has been given renewed impetus by a series of recent studies suggesting that the rapid pace of improvement in British longevity is now slowing. The Continuous Mortality Investigations group, which produces longevity projections based on the experience of insured and pensioned lives, found that longevity for men at age 65 fell by six months to 22.2 years while that of women fell by eight months to 24.1 years. While longevity is still expected to be higher than it is today, it is by a smaller margin than earlier forecasts. PwC, the professional services firm, recently produced a study concluding that as much as £310bn could be wiped from the liabilities of UK defined benefit schemes. Although a respected group of actuaries hit back, describing the assumption as “extreme”, the entire debate has escalated to the political arena.

A backdrop to the discussion is the fact that increases in the age at which state pensions are payable is open for debate. In thinking about the rate at which state pension ages rise, the UK Government Actuary's Department assumes — as does the Office for National Statistics — that, in future, longevity will rise at the same pace it has for the past century; that is, 1.2 per cent each year. That could change with new data to be released in the autumn.

But history suggests there are good reasons to take a very long view when making longevity assumptions, rather than be distracted by short-term fluctuations. In the 60 years between 1911 and 1971, the life expectancy of men reaching 65 rose by 1.34 years before falling back. That is a rate of roughly 0.6 per cent annually, about half the rate built into the GAD forecast. But in the next 20 years to 1991, males of 65 years gained, on average, another two years, and from that point onwards, the rise was increasingly rapid.

Moreover, a look outside Britain's borders tells us that longevity will keep rising. Physiologically, all humans are pretty much the same, even if we look different. And while environmental and behavioural differences will affect longevity, there is no underlying biological reason why lifespans should differ by country. Data from the UN show that people in China, Italy, Spain, Japan and Sweden are already outliving the British.

The science behind human longevity suggests that forecasting the outer limits of lifespans is a wasted exercise. Professor Thomas Kirkwood of the Institute for Ageing at Newcastle University, rejects the notion that humans are “programmed” to die and says there is no evidence of this in evolutionary biology. Cells have the capacity to repair themselves, but successive damage, through illnesses, poor nutrition or accidents, eventually undermines their ability to self-repair. That provokes the process of ageing. But as large numbers of people enter old age with far less cellular damage than their parents and grandparents, they are better able to withstand shocks. This process has extended lifespans and made healthy lives at older ages possible.

In the 19th and early 20th centuries, actuaries at insurance companies sought to find a “law of mortality” that would allow them to price the risk of death accurately. The industry clubbed its data together in 1847 and again in 1870 and found that, for its customer base, not much had changed. But a further review in 1893 produced a shock: the rate of death among women aged 60 — to whom the insurance industry had sold annuities — had fallen by over half since the previous investigation. Unwittingly, the industry had begun to swap mortality risk for longevity risk and at cost to itself.

Scientific intervention has thus rendered an uncomfortable answer to the question, “How long can human beings live, anyway?”. The answer is that we do not know.