subject: Lifespan And Life Expectancy [print this page] The ageing process begins at conception and continues until death. This at any rate is what is meant by biological ageing, since it potentially includes all the changes that come about through growth and development from fertilized ageing to newborn baby, allowing also for maturation to adulthood, and for the secondary effects of illness, disease and natural degeneration. Generally speaking, however, by 'ageing' we refer to the period of time after the individual has passed his or her biological peak. Effectively, this is the Third Age of man.
Among gerontologists (the scientists who study the ageing process, as opposed to geriatricians who are physicians for the elderly) there is debate about the relevance of biological and chronological age. The two may mean the same thing if an individual seems (biologically) to be as old as his years. It would be nice if the correlates were strong enough to predict the life expectancy of the individual on this basis, but this is not the case.
It is a fact that the population structure of Britain and most other developed countries has change dramatically over the last hundred or so years. Whereas at the turn of this century the proportion of people over the age of 65 was around five per cent, it is now almost seventeen per cent. Admittedly, one has to consider that over this period of time the birth rate has halved, and the number of young people who have died from infectious diseases has dripped considerably. Nevertheless, there are currently more people over the age of 65 than have ever been over 65 since cumulative human history began.
At the time of the Ancient Egyptians 40 years would have been considered a good age, while 65 would have seemed positively ancient. The Bible tells us that the allotted span was some three score years and ten, although relatively few people would have lived that long. Again, forty years would have been nearer the mark. There is a distinction to be made here between lifespan and life expectancy. The 'lifespan' is the potential which an individual could live if they are fortunate to be unhampered by accident or disease. As mentioned above, according to the Bible it was 70 years.
'Life expectancy' on the other hand, is a statistical expression of how many years a member of a group with similar life characteristics can expect to live. Using life tables it is then possible to say what the expectation of life is for a certain group at birth or at any specific age, As an example, the life expectation for a female born in Britain in 1841 was 42 years, but if she lived to 65 years her further expectation was 11.6 years. Now, in 1992 the life expectation for a female e would be 75 years at birth, and 16 years at 65.
It is further interesting to note that the expectation at 65 did not increase until about 1930. The significance of this is that the number of people living past the age of 75 is getting greater, so that by 2001 it is estimated that there will have been an increase of forty per cent based on figures for 1980. Further, there will have been an increase of fifty per cent for the over 85s.
by: Rashid Javed
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