Making Sense of Centenarians; Genes and Lifestyle Help People Live through a Century
Christensen, Damaris, Science News
My great-grandmother was born in 1897. She did most of her cooking on a wood-burning stove in her farmhouse in Cable, Wis. When I knew her, she slept on a cotton mattress that she had made herself in the 1940s and kept handmade lace doilies on the arms of all the chairs and sofas.
When I asked her to tell me what it was like living in the Roaring '20s and the Depression, I expected her to regale me with stories of wild dancing and ruined investors jumping from skyscrapers. Instead, Elizabeth Morey told me of logging, raising chickens, and cooking on a wood stove--stories typical of people living in rural Wisconsin during those times.
What wasn't typical about my great-grandmother was just how long she was able to tell her stories: She died in 1999, just shy of her 102nd birthday.
Although only about 1 in 10,000 people in developed countries live to be a hundred or more, these centenarians constitute one of the fastest-growing age groups in the United States. As sociologists, gerontologists, and other investigators collect centenarians' stories--and analyze their genes--these oldest old are transforming the way people think about aging.
The U.S. Census Bureau estimates that there were between 69,000 and 81,000 centenarians living in the United States in 2000. With current population trends in developed countries, the number of centenarians should double every 10 years, says John R. Wilmoth of the University of California, Berkeley.
Over the past 150 years, the average life span--and correspondingly, the maximum life span--has been steadily increasing, Wilmoth says. Since 1969, the estimated maximum age that people reach has increased by about a year every decade, he and his colleagues reported in the Sept. 29, 2000 SCIENCE. The team based its findings on data from Swedish populations from 1861 to 1999. The maximum estimated life span in that country is now about 108 years. (The longest documented human life was of Jeanne Calment, a Frenchwoman who died at age 122.)
Much of the rise in average and maximum life span is attributable to the increased life expectancy for healthy people over 70, Wilmoth says. "It's very important for people who are older and healthy to realize that their life expectancy is probably going to be longer than the rest of their peers and prepare accordingly," Wilmoth notes.
What lifestyle can these people expect?
Researchers divide centenarians into three roughly equal-size groups, based on how well they function and the severity of illness or disability they have, says Peter Martin of Iowa State University in Ames. Perhaps 30 percent of centenarians are both mentally and physically impaired by the time they reach 100. Another 40 percent have limitations to their vision, hearing, or mobility--and perhaps some mental impairment--but are able to function reasonably well. And another 30 percent--the population segment that fascinates both researchers and the public--show few signs of mental or physical impairment and are often still living independently.
Like most people who live to be 100 or older, my great-grandmother was ill only in the last few years of her life. Among centenarians in a New England study, almost 90 percent had been living independently when they were 92 years old. About 73 percent of the group had been independent when they were 97, and almost 35 percent of them were still independent when they were surveyed.
"People are ingrained with the idea that the older you get, the sicker you get," says Thomas Perls of Beth Israel Deaconess Medical Center in Boston and director of the New England Centenarian Study. "It's rather the older you get, the healthier you've been .... Compared with others in the older population, centenarians seem to either markedly delay, or in some cases, escape life-threatening diseases such as cancer and Alzheimer's disease."
Although male centenarians are fewer, they're often less likely to have significant mental or physical disabilities than are women who reach 100 are, says Margery Silver, also of Beth Israel Deaconess. …