Will you live to 100? Consider the odds, take a test

Today's babies will be tomorrow's centenarians. A new report says that reaching the age of 100 may become ordinary for most American babies born since 2000. How will living for a century affect our kids? And what quality of life awaits those who live this long?

• The news: Life expectancy has been increasing steadily in developed countries such as the United States, France, Germany, Italy, the United Kingdom, Canada and Japan. If this pace continues, reaching the age of 100 will become ordinary for most people in those countries, according to a report published earlier this month in The Lancet. Researchers at the Danish Aging Research Centre at the University of Southern Denmark predict society will stop looking at life in three phases (childhood, adult and old age) and instead start dividing old age into a "third age (young old)" and a "fourth age (oldest old)."

• The rates: Japan now has the world's longest life expectancy — 83 years for babies born in 2007, according to the World Health Organization. The U.S. life expectancy is 77.9 years for babies born in 2007, according to preliminary data from the Centers for Disease Control and Prevention. The number of people age 100 or over in the United States has doubled since 1990 and is 16 times the number of centenarians in 1950. According to the U.S. Census, there were an estimated 96,548 centenarians in the United States as of November 2009.

• Is it healthy? There isn't much data on the health of people over age 85, but many are optimistic that earlier detection and better treatment of conditions like cancer and heart disease will make life healthy for people in their "fourth age." The New England Centenarian Study found that a quarter of 169 centenarians studied were free of any significant cognitive disorders and even surpassed the research interviewers on some mental tests. About 15 percent lived independently in their own homes, some held jobs, and most were uncommonly healthy until the end of their lives. As a group, people 100 and older are actually healthier than people 20 years their junior.

• Longevity gene: A variation in a gene called FOXO3A is found much more often in people living to 100 and beyond, according to a report published in the Proceedings of the National Academy of Sciences earlier this year. The gene is credited with longer lives for some, but researchers say other factors are involved, too.

• Who lives this long? The New England study found that most centenarians share these characteristics: emotional resilience (ability to adapt to life's events), self-sufficiency, intellectual activity, a good sense of humor (including about themselves), religious beliefs, strong connections with other people, low blood pressure, appreciation of simple pleasures, a zest for life, don't currently smoke or drink heavily, may play musical instruments and follow an anti-inflammatory diet (like the Mediterranean diet) that has been linked to longevity. About 80 percent of all Americans over the age of 100 are women and most of them gave birth to children after age 40.

• Calculate your age: Researchers involved in the New England study have a Web site with a "Living to 100 Life Expectancy Calculator" that uses scientific data to estimate how old you will live to be. The calculator asks 40 questions related to health and family history, and takes about 10 minutes to complete, www.livingto100.com.