The article, appearing in the medical journal The Lancet, shows that based on current trajectories, more than half of all babies born in industrialized nations since the year 2000 can expect to live into the triple digits. The trends included in the article show that many Western nations will have most people living past 100, with half of all babies born in 2007 in the U.S. likely to live to age 104.
"I guess it's good news for individuals and a challenge for societies," said Dr. Kaare Christensen, an epidemiologist with the Danish Aging Research Center at the University of Southern Denmark, the study's lead author.
"If this trajectory continues, half the babies will be 100 and I think that gives us a new perspective for how to plan your life, basically," he said. "If you're going to retire when you are 60 or 65, it looks quite different when your life expectancy is 75 or 80 than when it's 100."
Christensen said that while the progress in life span during the first part of the 20th century came by reducing infant mortality, increases in longevity since then have come from improving life at older ages, and that will need to persist for the projection to hold up.
"If we want to have a continuing increase in life expectancy, the progress has to occur at older ages," he said. "I don't hear any concerns among the elderly that they are living too long."
Christensen said that the aging population will also likely be a more vibrant population, with a higher quality of life than people of that age now.
"The good news is people will generally be functioning well -- it's more like they're postponing their aging process," he said.
Some researchers backed the new report's hypothesis.
"Based upon the best possible approximations, I believe they are correct in their assessment of age projections," said Dr. Stephen Helfand, a professor in the division of biology and medicine at Brown University in an e-mail. "Their evidence appears overwhelming in favor of their hypothesis.
At the same time, some question whether the full prediction -- that most babies born today will live past 100 -- is fully accurate.
"I think that's a very optimistic scenario; however, there may be chronic health problems that may not allow us to follow that best-case scenario, not yet," said Hector Gonzalez, an assistant professor of medicine and public health at Wayne State University.
"There's no reason to think more than half the population living today can't live until 100," said Dr. Harrison Bloom, senior associate at the International Longevity Center of New York. "But that would assume better eating habits, a healthier lifestyle and continuing improvements in the environment. That lifestyle would definitely mean less obesity. The diabetes and obesity epidemic today is very real. A lot of people are going to die earlier than their projected life span would have been."
Changes for an Aging Population
Regardless of age, researchers agreed that we are seeing a change in population demographics that will alter how society functions.
"There are many significant consequences to an increase in longevity, which are obvious to most people," said Helfand. "People living longer will change the entire demographics and, perhaps, needs of a nation. "
"More older persons living longer and living better -- there will also be an absolute increase in persons with disability and requiring care," said Dr. Eric B. Larson, executive director of the Group Health Research Institute in Seattle. "This will cause us to need to rethink health care for all ages, but especially for seniors -- most likely this would mean a focus more on rehabilitation and pre-habilitation, health and functional maintenance and less focus on individual sickness and acute care."
Some worry that changes that come may not be positive.
"Unfortunately, I think what we're seeing, especially with the obesity epidemic, is people are living longer, but they're not necessarily healthier, and that's where we really need to focus," said Gonzalez. "That's a huge economic burden, to take care of a lot of sick people.
"I'm a little troubled, actually, that society is aging, and a large proportion of the older population will be made up of a lot of skilled workers. My chief concern is that right now we have gutted a lot of our educational opportunities and that we may not have the skilled work force necessary to support an older population."
Gonzalez said part of the problem is reflected in ethnic disparities, where minorities -- who will make up an increasing percent of the population -- have more health problems and less education.
Others noted that while disparities are present, there is also an increasing, vital group of older people that is likely to continue growing, even if it will not be a majority of the country in a century.
"A large percent of the older population is still very active physically and cognitively. It's definitely true that there will be a lot more people over 100," said Bloom.
Older But Wiser?
Changing demographics may mean some unprecedented changes in the work force as well, particularly since many are likely to keep working longer.
"That will be one of the major challenges, to keep the elderly in the workforce, and at the same time to make work for the younger generations," said Christensen. "That's for sure going to be something that requires a lot of new thinking. That will be a new situation."
But an increasingly older population may have some benefits over the present demographics.
"One commodity that may emerge is an increase in wisdom," said Helfand.
"It appears that wisdom, or an ability to compromise, does come with age," he said. "Having more people with experience -- not just technical, but also emotional and psychological experience -- should be beneficial. (For example, it often takes older statesmen to make compromises that will benefit their country's longer term benefit, than younger less compromising statesmen.) Time -- age -- usually improves decision-making."