More than half of all of those born in developed countries will live to be 100 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 suggested that this may be mitigated by people not only living longer, but also staying healthier in their later 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 says in a study published 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 developed nations.
This means smaller workforces in developed nations will have to shoulder an even-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 ageing populations.
'If people in their 60s and early 70s worked much more than they do nowadays, then most people could work fewer hours per week,' researchers wrote in the study.
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.
