More than half of babies born today in affluent homes are expected to live to the age of 100, based on current life expectancy trends.

Analysis of life expectancy and the quality of life in older age indicates that ageing processes can continue to be extended.

Using demographic modelling, scientists calculated that the average British child born in 2007 could expect to live to 103, while in Japan they would live to 107.

Experts made the prediction in a review of the latest research evidence in The Lancet medical journal, published today. They pointed out that huge increases in life expectancy, amounting to more than 30 years, had been seen in most developed countries during the 20th century.

Death rates in nations with the longest life-spans, such as Japan, Sweden and Spain, suggest that even if health conditions do not improve, three quarters of babies will live to 75. If present trends continue, most of those born in well-off countries since 2000 are likely to celebrate their 100th birthdays.

Kaare Christensen, from the Danish Ageing Research Centre at the University of Southern Denmark, said that increases in life expectancy since 1840 showed no sign of slowing, helped by medical advances, better nutrition and improved living conditions.

He said that many issues were posed by a large, active, increasingly elderly population — such as the “Prince Charles scenario” where people could find themselves waiting for the most senior post in an organisation for decades.

“So few people die at an early age now, so we do not expect substantial improvement at a younger age. Instead, it will be at older age. This will be because of high-tech advances, such as mobility and medication, but also low-tech advances such as keeping elderly people a part of active society,” he said.

“This will require some thought.

“If you end up with people holding very senior positions to a very high age then you need to make sure there is some way that you can still bring in fresh blood.”

Writing in the paper, The multinational research team concludes that mortality among people older than 80 years of age is still falling in rich nations. Data from more than 30 developed countries showed that in 1950 the probability of living from 80 to 90 was 15 per cent for women and 12 per cent for men. In 2002, these figures had risen to 37 per cent and 25 per cent respectively.

“If life expectancy were approaching a limit, some deceleration of progress would probably occur. Continued progress in the longest-living populations suggests that we are not close to a limit, and a further rise in life expectancy seems likely.”

Other evidence indicated that people were not only living longer but managing to preserve their quality of life despite rising rates of chronic illnesses such as cancer.

Disability prevalence, as measured by the ability of people to carry out day-to-day activities such as dressing and feeding themselves, appeared to be falling.

One series of studies had reported larger improvements in disability-free life expectancy than overall survival.

Research from Denmark showed that the proportion of individuals who retained their independence was similar among those aged 92-93 and those aged 100.

Exceptional longevity did not necessarily lead to exceptional levels of disability. However, the authors proposed the redistribution of employment as a possible solution to the overall financial burden of ageing populations. Containing large numbers of people who do not work was causing concern, said the authors.

“If people in their 60s and early 70s worked much more than they do nowadays, then most people could work fewer hours per week than is currently common — if they worked correspondingly more years of their longer lives,” they said.

“Preliminary evidence suggests that shortened working weeks over extended working lives might further contribute to increases in life expectancy and health. Redistribution of work will, however, not be sufficient to meet the coming challenges. Even if the health of individuals at any particular age improves, there could be an increased total burden if the number of individuals at that age rises sufficiently.”

They concluded: “Increasing numbers of people at old and very old ages will pose major challenges for healthcare systems. Present evidence, however, suggests that people are not only living longer than they did previously but also they are living longer, with less disability and fewer functional limitations.”

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