Compression of morbidity: postponing human aging

This is Dr. James Fries, and I'll be talking with you today on the compression of morbidity and the ways that we have of postponing human aging.

Underlying our current knowledge of human aging are a number of central, rather simple but often not familiar facts. The first number of slides we'll go through these, and I'll try and explain them as we go through. The current slide shows life tables from the United States at 20 year intervals from 1900 to 1980. Notice several things about the way in which people die. They begin at the left side of the slide, with zero deaths at age birth. And then as they progress through life to age 100 or so, the curves develop depending upon the year of birth and are quite different from each other. In 1900, for example, there are many early life deaths, or births and deaths, and that causes the curve to go down steeply, and then to continue on throughout the lifespan, and then to emerge at the bottom line at around age 100 or so. The second curve is 1920, 20 years later. In it, there are fewer early life deaths, and the line continues, as shown. And again, it inserts at the age of 100 or so. The same thing happens in 1940, in 1960, in 1980 until we look at the present curve, which would fit in between the 1980 curve and the top of the slide. There is very little room for improvement any more below age 50. If you take a look at age 50 and just draw a line in your mind, going up from the bottom line to the second one, you'll see that almost all of the space that was previously available is now not possible, and there's only a narrow little sliver of people who are dying before the age of 50. So the curves continue, and the most noteworthy thing about this slide is that these kinds of curves all insert at the same place. That indicates that the lifespan, which is taking over for diseases, which are what we're usually counting, the lifespan is fixed from decade to decade, and that has continued through the present. When we are seeing improved longevity, as we are in most developed countries, that is due to a decrease in early life deaths and not to the force of mortality in some broader way being abated. This is a cause of a lot of misstatement of facts about human aging. This would indicate here that human survival has been fixed at least for the past 115 years. So the human lifespan is biologically limited, but our attention needs to be placed on the age at first morbidity. Now, I'll use morbidity a lot. It's in general synonymous with the term "disability," or inability to perform activities of daily living. "Morbidity" is the term which we frequently oppose to mortality, and we use morbidity to indicate everything that is part of illness but doesn't result in death.