More than half of babies now born in the UK and other wealthy nations will live to 100 years, researchers say.
Data from more than 30 developed countries shows that since 1950 the probability of surviving past 80 years of age has doubled for both sexes.
Professor Kaare Christensen, of the Danish Ageing Research Centre at the University of Southern Denmark, who led the study, said life expectancy had been increasing since 1840 and there was no sign of this trend slowing down.
Four 'ages of man'
The researchers said that man could now be regarded as having four stages of life - child, adult, young old age and old old age.
They said there was no evidence that the old old age group were unhealthier than their younger counterparts, partly because the frailest people died first, leaving the most robust to survive past 85.
And a study of US super-centenarians (age 110 to 119 years) showed that, even at these advanced ages, 40% needed little assistance or were independent.
People are not only living longer than they did previously, but also they are living longer, with less disability and fewer functional limitations .