Wednesday, September 24, 2014

Are We Living Longer, or Just Dying More Slowly?

Humans are clearly living longer today than they did a century ago.  Given continuing advances in medical knowledge and technologies, it is easy to conclude that life expectancies can and will continue to increase.  Gregg Easterbrook considers that notion in an interesting article in The Atlantic: What Happens When We All Live to 100?  He performs extrapolations of current and past data to suggest what might be possible.

“Life expectancy at birth has risen steadily in the United States.  If it continues to increase at its average historic rate—an aggressive assumption—it would reach 100 in 2084.  At the average rate of increase since 2000, which has been slower, life expectancy at birth would be 91 in 2084.”

Extrapolating the data as done in the chart is aggressive.  Easterbrook seems to be philosophically aligned with such an optimistic projection, but he provides a balanced discussion of why this future may or may not come to pass.   For the pro-argument he quotes James Vaupel, the founder of Germany’s Max Planck Institute for Demographic Research.  For the con-argument he turns to Jay Olshansky, a professor of public health at the University of Illinois at Chicago.

“In 2002, Vaupel published an influential article in Science documenting the eerily linear rise in life expectancy since 1840. Controversially, Vaupel concluded that ‘reductions in mortality should not be seen as a disconnected sequence of unrepeatable revolutions but rather as a regular stream of continuing progress’.  No specific development or discovery has caused the rise: improvements in nutrition, public health, sanitation, and medical knowledge all have helped, but the operative impetus has been the ‘stream of continuing progress’.”

“Vaupel called it a ‘reasonable scenario’ that increases will continue at least until life expectancy at birth surpasses 100. His views haven’t changed. ‘The data still support the conclusions of the 2002 paper. Linear rise in life expectancy has continued,’ Vaupel told me earlier this year.”

Olshansky provides a counter argument.

“On the opposite side of this coin, Olshansky told me the rise in life expectancy will ‘hit a wall soon, if it hasn’t already.’ He noted, ‘Most of the 20th-century gains in longevity came from reduced infant mortality, and those were onetime gains.’ Infant mortality in the United States trails some other nations’, but has dropped so much—down to one in 170—that little room for improvement remains.”

“’….Changes in medicine or lifestyle that extend the lives of the old don’t add much to the numbers.’ Olshansky calculates that if cancer were eliminated, American life expectancy would rise by only three years, because a host of other chronic fatal diseases are waiting to take its place. He thinks the 21st century will see the average life span extend ‘another 10 years or so,’ with a bonus of more health span. Then the increase will slow noticeably, or stop.”

Easterbrook seems to sense that a game-changer is required if his centenarian future is to ever arrive.  Some people believe that many of the debilitating and life-threatening chronic diseases are, in fact, aided and abetted by the aging process itself.  If the body’s mechanisms could be controlled by drugs or other treatments, the impact of these conditions might be considerably diminished.

“Aging brings with it, of course, senescence. Cellular senescence, a subset of the overall phenomenon, is a subject of fascination in longevity research.”

“The tissues and organs that make up our bodies are prone to injury, and the cells are prone to malfunctions, cancer being the most prominent. When an injury must be healed, or cancerous tissue that is dividing must be stopped, nearby cells transmit chemical signals that trigger the repair of injured cells or the death of malignant ones. (Obviously this is a simplification.) In the young, the system works pretty well. But as cells turn senescent, they begin to send out false positives. The body’s healing ability falters as excess production of the repair signal leads to persistent inflammation, which is the foundation of heart disease, Alzheimer’s, arthritis, and other chronic maladies associated with the passage of time.”

Much of Easterbrook’s article is devoted to assessing progress in research aimed at controlling the body’s aging mechanisms.

In the same issue of The Atlantic as Easterbrook’s article was another that looked at aging from a different perspective and suggested that living until 100 is neither likely nor desirable.  Ezekiel J. Emanuel (yes, one of the Emanuel brothers) provided this intriguing title: Why I Hope to Die at 75.  He provides this lede:

“An argument that society and families—and you—will be better off if nature takes its course swiftly and promptly”

Emanuel’s decision that there is an age beyond which it is no longer wise to take measures to extend one’s life is interesting in itself, but will have to be saved for discussion at another time.  What is of interest here is his conclusion that what we are observing in recent years is not an extension in living, but an extension of the dying process.  Life extension is not adding to the quality of life.

“Since 1960….increases in longevity have been achieved mainly by extending the lives of people over 60. Rather than saving more young people, we are stretching out old age.”

“The American immortal desperately wants to believe in the “compression of morbidity.” Developed in 1980 by James F. Fries, now a professor emeritus of medicine at Stanford, this theory postulates that as we extend our life spans into the 80s and 90s, we will be living healthier lives—more time before we have disabilities, and fewer disabilities overall. The claim is that with longer life, an ever smaller proportion of our lives will be spent in a state of decline.”

“Compression of morbidity is a quintessentially American idea. It tells us exactly what we want to believe: that we will live longer lives and then abruptly die with hardly any aches, pains, or physical deterioration—the morbidity traditionally associated with growing old. It promises a kind of fountain of youth until the ever-receding time of death. It is this dream—or fantasy—that drives the American immortal and has fueled interest and investment in regenerative medicine and replacement organs.”

To support the claim that compression of morbidity is a fantasy, Emanuel describes results obtained by Eileen M. Crimmins and Hiram Beltran-Sanchez: Mortality and Morbidity Trends: Is There Compression of Morbidity?  Their paper appeared in 2011.  Two of the tables summarizing their data are reproduced below.  There is much of interest here.

Here is Emanuel’s summary of the study results:

“….using data from the National Health Interview Survey, Eileen Crimmins, a researcher at the University of Southern California, and a colleague assessed physical functioning in adults, analyzing whether people could walk a quarter of a mile; climb 10 stairs; stand or sit for two hours; and stand up, bend, or kneel without using special equipment. The results show that as people age, there is a progressive erosion of physical functioning. More important, Crimmins found that between 1998 and 2006, the loss of functional mobility in the elderly increased. In 1998, about 28 percent of American men 80 and older had a functional limitation; by 2006, that figure was nearly 42 percent. And for women the result was even worse: more than half of women 80 and older had a functional limitation. Crimmins’s conclusion: There was an ‘increase in the life expectancy with disease and a decrease in the years without disease. The same is true for functioning loss, an increase in expected years unable to function’.”

And here is the more succinct summary:

“As Crimmins puts it, over the past 50 years, health care hasn’t slowed the aging process so much as it has slowed the dying process.”

It is worth spending a few moments examining the data in the tables above.  We seem to be living longer, but we are getting sick earlier and losing physical functionality earlier—and this is apparent in all age groups, not just old people.  As we continue to pump chemicals—both environmental and medical—into our bodies, change the nature of the food we eat, and alter the bacterial composition our bodies depend on, we find that we are no longer the animal that evolution designed.  Perhaps therein resides the reason(s) why we find ourselves becoming less healthy.  Perhaps we should understand what we have already done to ourselves before we inflict on ourselves another grand experiment with unknown consequences.

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