Life Expectancy Statistics and Some Thoughts
Here are some life expectancy and mortality statistics; a comparison between figures for 2002 and 2003 show the rate of increase is continuing much as expected.
Life expectancy for Americans reached an all-time high of 77.6 years in 2003, and the gap between men and women narrowed, according to preliminary results from state death certificates released Monday. According to the report from the National Center for Health Statistics, life expectancy was up from 77.3 years in 2002.
With aging taken into account, death rates declined for eight of the 15 leading causes of death, including the two leading causes -- heart disease (down 3.6 percent) and cancer (down 2.2 percent). Declines were also noted for stroke deaths (4.6 percent), suicide (3.7 percent), flu-pneumonia (3.1 percent), chronic liver disease and cirrhosis (2.1 percent), and accidents/unintentional injuries (2.2 percent). Mortality increased by 5.9 percent for Alzheimer's disease, and by 5.7 percent due to hypertension, 3.4 percent for Parkinson's disease and by 2.1 percent for kidney disease.
I should note, for those of us who aren't statisticians, that life expectancy in this sense doesn't necessarily have much to do with longevity or longevity projections:
Life expectancy [at birth] is a measure of current conditions. It is not a prediction about how long somebody will live. But it's a measure of how long a person, a baby would live if that baby was confined to this year, could not get out of this year, was stuck with the conditions of this year.
In other words, it's a useful measure of how (and how well) medical science is progressing over the years, but it isn't a prediction of life span in the actual, ever-changing real world. From the very high level perspective, decreasing mortality rates for various diseases are a sign of progress across the board in medical technology. Increasing mortality rates - especially in neurodegenerative diseases - are a sign of longer life spans running into progressive degenerative conditions we still know little about ... along with increasing obesity and all that comes with it.
If you accept the premises of the Reliability Theory of Aging, it is clear that most improvements in medicine will lead to some degree of incidental healthy life extension. Your body is a complex machine; on average, and absent bad luck, better preventative maintenance and repair will lead to a longer, healthier life span. The trouble - from my point of view - is that incidental healthy life extension isn't providing anywhere near large enough gains. We need to invest much more time, effort and money into medical research if we want to reach "acturial escape velocity", the point at which medical science allows remaining life span to increase more than a year each year. This will likely require directed research into the root causes of aging, rather than the continual accumulation of specific cures and generally better preventative medicine.
A final thought on this topic from Ian Clements:
But [life spans] have STEADILY increased - and THAT is the point. There is a linear increased lifespan for all adult ages, including the very old, over the recorded couple of centuries we've had figures. This is the basis for maintaining that there is no 'natural' upper limit; if there was, then the increase in lifespans would be levelling off.
So don't let's worry that the increases are small, but note that they are continuously linear (or even increasing). This gives hope that we can uncover the mechanisms which cause steady degeneration, and slow or reverse them.