A new approach to understanding the process of ageing is the subject of an essay by Leonard Hayflick, an anatomist of the University of California, in Nature for January 27. Hayflick asserts that our study of the ageing process during the past three decades has been prompted more by the politics of population increase than by any advance in our understanding of its biology.
During the past century, life expectancy at birth in developed countries has increased from about 48 to 76 years, a similar increase to that over the previous 1,900 years. The life expectancy of 20 in ancient Rome is explained by a high death rate in early childhood, as in modern developing countries. Expansion of life expectancy in children has been brought about by control of infectious diseases, but in older people the chronic killer diseases such as cancer and cardiovascular disease have made relatively little response to research.
Failure to distinguish between disease in old age and the ageing process itself is widespread, even among scientists. Humans and their pets and protected species are the only organisms where large numbers undergo ageing changes, and without human impacts wild animals show no such large proportion of aged individuals. From this angle, ageing might be regarded as an artefact of civilisation.
It is virtually impossible, writes Hayflick, to raise funds for research on ageing itself, because policy makers and the public believe that no one suffers or dies from it. The belief is that we suffer and die from the diseases that make their impact during our ageing process. In fact, such diseases occur because ageing increases our vulnerability to them. The vast amounts spent on researching Alzheimer's disease, for instance, will do nothing to advance our knowledge of the biology of ageing, and will have only a trivial effect on life expectancy.
What we need to consider is why old cells are more vulnerable to disease than young ones. That is the question.