LONDON (Reuters) - More than half of babies born in rich nations today will live to be 100 years old if current life expectancy trends continue, according to Danish researchers.
Increasing numbers of very old people could pose major challenges for health and social systems, but the research showed that may be mitigated by people not only living longer, but also staying healthier in their latter years.
"Very long lives are not the distant privilege of remote future generations -- very long lives are the probable destiny of most people alive now in developed countries," Kaare Christensen of the Danish Ageing Research Centre wrote on Friday in a study in the Lancet medical journal.
The study used Germany as a case study and showed that by 2050, its population will be substantially older and smaller than now -- a situation it said was now typical of rich nations.
This means smaller workforces in rich nations will have to shoulder an ever-greater burden of ballooning pension and healthcare requirements of the old.
Many governments in developed nations are already making moves toward raising the typical age of retirement to try to cope with aging populations.
The researchers said this was an important strategy, and added that if part-time work was considered for more of the workforce, that could have yet more benefits.
"If people in their 60s and early 70s worked much more than they do nowadays, then most people could work fewer hours per week," they wrote. "Preliminary evidence suggests that shortened working weeks over extended working lives might further contribute to increases in life expectancy and health."
Christensen and colleagues said huge increases in life expectancy -- of more than 30 years -- had been seen in most developed countries over the 20th century.
And death rates in nations with the longest life-expectancy, such as Japan, Sweden and Spain, suggest that, even if health conditions do not improve, three-quarters of babies will live to celebrate their 75th birthdays.
"But should life expectancy continue to improve at the same rate, most babies born in rich nations since 2000 can expect to live to 100 years," they wrote.
The researchers, who pooled and analyzed data from several international studies, said they wanted to explore "a common view" that a big rise in the proportion of older people would come as a result of helping an increasing number of frail and ill people survive longer -- with huge personal and societal costs.
But they found that even though many people who live to age 85 have chronic diseases such as diabetes and arthritis, they have only become frail and disabled at a later stage, essentially postponing frail old age instead of extending it.
"This apparent contradiction is at least partly accounted for by early diagnosis, improved treatment, and amelioration of prevalent diseases so that they are less disabling," they wrote.
"People younger than 85 years are living longer and, on the whole, are able to manage their daily activities for longer."
But for people older than 85, the situation is less clear, the researchers said. Data are sparse, and there is widespread concern that exceptional longevity -- with ever larger numbers living to 100 and more -- could be grim for the people themselves and the societies they live in.