"We're living longer because people are reaching old age in better health," said demographer James Vaupel, author of a review article appearing in the March 25 edition of Nature. But once it starts, the process of aging itself -- including dementia and heart disease -- is still happening at pretty much the same rate. "Deterioration, instead of being stretched out, is being postponed."

The better health in older age stems from public health efforts to improve living conditions and prevent disease, and from improved medical interventions, said Vaupel, who heads Duke University's Center on the Demography of Aging and holds academic appointments at the Max Planck Institute for Demographic Research in Rostock, Germany, and the institute of Public Health at the University of Southern Demark.

Over the past 170 years, in the countries with the highest life expectancies, the average life span has grown at a rate of 2.5 years per decade, or about 6 hours per day.

The chance of death goes up with age up until the most advanced ages. The good news is that after age 110, the chance of death does not increase any more. The bad news is that it holds steady at 50% per year at that point, Vaupel said.

"It is possible, if we continue to make progress in reducing mortality, that most children born since the year 2000 will live to see their 100th birthday -- in the 22nd century," Vaupel said. If gains in life expectancy continue to be made at the same pace as over the past two centuries, more than half of the children alive today in the developed world may see 100 candles on their birthday cake.

This leads to an interesting set of policy questions, said Vaupel. What will these dramatically longer lifespans mean for social services, health care and the economy? Can the aging process be slowed down or delayed still further? And why do women continue to outlive men -- outnumbering them 6 to 1 at age 100?

It also may be time to rethink how we structure our lives, Vaupel said. "If young people realize they might live past 100 and be in good shape to 90 or 95, it might make more sense to mix education, work and child-rearing across more years of life instead of devoting the first two decades exclusively to education, the next three or four decades to career and parenting, and the last four solely to leisure."

One way to change life trajectories would be to allow younger people to work fewer hours, in exchange for staying in the workforce to a later age. "The 20th century was a century of the redistribution of wealth; the 21st century will probably be a century of the redistribution of work," Vaupel said.

Note: If no author is given, the source is cited instead.

• Healthy Aging
• Children's Health
• Teen Health
• Workplace Health
• Health Policy
• Chronic Illness

• Longevity
• Fertility
• Senescence
• Growth hormone treatment
• Huntington's disease
• Bone age