Part 2 of 2
SAN FRANCISCO, Nov. 24 (UPI) -- Even the experts fail to reach a consensus in projecting the future of human longevity.
James Vaupel of the Max Planck Institute for Demographic Research in Germany and Duke University in North Carolina has used statistical analysis to find over the past 160 years, human life expectation has been increasing at about 30 months every decade.
James Carey of the University of California, Davis, found Vaupel's projections compelling and convincing.
"It seems to me that the human species is mechanically (bones, organs, etc.) capable of supporting life with some repair from the low- to mid-100-year range (e.g., 130 to 150 years)," Carey told United Press International.
In contrast, Leonard Hayflick, known as the father of cellular gerontology, said his pioneering aging research over the past 45 years has convinced him of a fixed life span.
Though Hayflick acknowledges life expectancy took a leap between the 19th and 20th centuries, "such an extraordinary jump in such a short time has never occurred before, and the likelihood of it recurring is about as much as your being stuck by a meteor in the next few minutes," he said in a telephone interview.
It is neither probable nor desirable Jeanne Calment's longevity record be broken, Hayflick asserted, referring to the unprecedented, authenticated longevity of the Frenchwoman who died at age 122 seven years ago. His discovery that cells have a finite capacity to divide -- a feature dubbed the Hayflick Limit in his honor -- ran contrary to the accepted scientific dogma of the time and changed the course of aging and cancer research.
"Everything in the universe ages ... why people believe they can somehow make themselves immortal and violate the fundamental laws of physics is beyond my understanding," said Hayflick, author of "How and Why We Age" (Ballantine Books, 1994). "I don't see any scenario that would benefit individuals or society in general by having the power to increase human longevity."
That sentiment applies to his own.
"My ideal goal is to live until the age of 100 and drop dead on my 100th birthday with full cognitive and physical abilities," confided the 75-year-old past president of the Gerontological Society of America, who also is a founding member of the Council of the National Institute of Aging and professor of anatomy at the University of California, San Francisco, School of Medicine.
Just as human cells begin to deteriorate as they approach the Hayflick limit in his laboratory studies, so, too, they likely undergo a similar process as they near the end of their life span in the human body, he proposed. The breakdown leaves them ever more vulnerable to disease and other stresses.
Curing cancer, stroke, heart disease and all other common causes of death in the elderly would add only 15 years to humans' life expectancy, he estimated.
"People believe we are spending billions on aging research, yet, in fact, it's less than 5 percent of the budget of the National Institute on Aging," Hayflick told UPI. "In comparison, more than half is spent on Alzheimer's disease, which, if eliminated, will add a mere 19 days to one's life."
Rather than trying to find a cure for every age-related condition, Hayflick suggests, why not address the more fundamental cellular question? Understanding why old cells are more vulnerable than young ones to disease could lead to methods of strengthening their resistance, and increasing seniors' ability to stave off the ailments of old age, he asserted.
The current life expectancy for all races in the United States is 74.4 years for males and 79.8 years for females. For whites, the figures stand at 74.9 and 80.1, respectively, Carey reported. That is in keeping with the rest of the developed world -- western Europe, North America, Japan, Australia and New Zealand -- where life expectancy currently ranges from the mid to high 70s, Carey said.
"In most developed countries, life expectancy at birth for women is between 78 and 85, and life expectancy for males is roughly five years less," Vaupel told UPI. "Japanese women currently enjoy the world's longest life expectancy: 85.23 years in 2002."
In 1840, that privilege belonged to Swedish women, with a life expectancy of 45 years, he added.
Throughout recorded history, men have never held the honor. Of the 654 documented supercentenarians -- those past their 110th birthday -- only a handful are male, Carey noted.
The gender gap -- which ballooned to a record 7.9 years in 1973 and 1975 -- has narrowed to a still significant 5.3-year margin, by which women anticipate outliving men.
"Males suffer higher death rates at all ages, even in utero," Vaupel pointed out. "Part of the gap is due to genetic differences between men and women (and) part is due to behavioral differences (which arise, in part, because of genetic differences)."
The sex-specific difference in death rates has puzzled Carey, but not as much as the absence of studies by gerontologists to look into the variation. "It is so important," he said.
His 14 years of experimental and comparative research have led Carey to three key conclusions:
-- Since life span is open-ended, though not limitless, there is no reason why longevity in humans could not continue to edge upward over the foreseeable and long-term future.
-- The gender gap in life expectancy will always exist, although the direction and rate of the change cannot be predicted.
-- The "morbid" stage preceding demise can be reduced, but not eliminated so there always will be a transition period from health to sickness to death.
Rather than trying to theorize about an upper age limit, researchers should try to determine how people would deal with another 30 to 50 years of life, he said.
"The life expectancy gains themselves will restructure society in ways that may or may not sustain further gains," Carey concluded. "These are inseparable because the economics, politics, science and so forth are inextricably tied to society."