"They said that I had the grip of a 17-year-old," says Mrs MacArthur, who lives in Cathays, Cardiff, and who is starting a full-time course in computing and mathematics in autumn. "Yet I eat all the wrong things and look the other way when exercise is mentioned. But it seems that I have done a lot of the right things unwittingly.
"I walk everywhere because I am too bored to wait for a bus, and have always carried heavy shopping and moved furniture, because I separated from my husband before my son was born 44 years ago, and had to cope alone. I also looked after my elderly parents for 16 years," she adds.
Mrs MacArthur was one of 200 people who took part in the experiment, run by the Biotechnology and Biological Sciences Research Council and Research into Ageing, in a Cardiff shopping centre last week. The results of the experiment will be announced at the British Association's Annual Festival of Science at the University of Wales, Cardiff, tomorrow.
"Of course it is hard to get meaningful data out of a trawl of 200 volunteers over three days in a shopping centre," says Professor Pat Rabbitt, professor of cognitive gerontology at the University of Manchester, who will announce the results. "But, like Fanny and Johnny Cradock, I will have the results of something I prepared earlier."
Professor Rabbitt's research in to the cognitive abilities of old people (with a base of 6,500 volunteers), shows that individuals can retain their mental agility, in certain areas and with practice, into extreme old age. It also shows that "most people trundle along to death with their wits still about them".
"Although the most reliable tests show a decline in cognitive function of 16 to 20 per cent after the age of 50, that means that we retain 80 per cent until death," he added.
His research is good news. It suggests the growth in those of pensionable age, from 10.7 million now to 11.8 million in 2010, may not be such a serious burden on the country's resources as was previously predicted.
In many ways, Mrs MacArthur is typical of today's older generation, in that she is entering the "third age" in much better shape than her parents did. Her healthy condition bears out the latest research, which suggests that we are not just living longer, but staying healthy longer. A new generation, not of grey panthers, but of grey cheetahs, is emerging.
The General Household Survey of 1996 showed that the proportion of elderly people who could not get about alone or manage household tasks had remained broadly constant since 1980, despite the ageing of the population. One- tenth say that they cannot walk down the road or get up and down stairs alone, and 16 per cent say they cannot do their own shopping.
Professor Tom Kirkwood, professor of biological gerontology at the University of Manchester, will discuss the reasons for this at tomorrow's conference. "Evidence suggests that people are reaching 85 in much better shape than previously, which is why the death rate among that age group is still falling. How long you live is determined by an interaction between genes and environment. Genes are important, but there is plenty of scope for lifestyle influences.
"We are living longer because the conditions to which we are exposed today are less severe than they used to be. We are enjoying better nutrition, less exposure to infectious diseases, and less physical stress."
Professor Kirkwood, who is responsible for much of today's thinking on ageing, has developed the "disposable soma theory". This says that we age because our bodies have evolved in such a way as to put only a limited investment into those cells (somatic, or body cells) that are not involved in reproduction.
Evolution's higher priority has been the germ cells, which are involved in reproduction and which have to be "immortal" to keep the lineage going. "The ageing process works through the life-long accumulation of damage to the body, rather than being clock-driven. Damage can occur in a number of ways, such as oxidation by free radicals, mutations and accumulation of faulty proteins. The body keeps repairing the damage for as long as possible, but eventually too much damage accumulates."
Professor Kirkwood says that in order to live longer we need to enhance the maintenance function of our body and reduce the damage to which our cells are exposed.
The fact that genes are important in determining longevity is good news for Mrs MacArthur, whose father and mother lived to 93 and 90 years respectively. She wants to live to a ripe old age because she has sole responsibility for her 44-year-old son, who is autistic. She took hormone replacement therapy for five years and has been told that her bone density is good. Now that she has been commended for her physical strength, she feels confident about her future. "I would like to become a computer programmer after I finish the course. I think life really begins at 71."Reuse content