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The Dementia Epidemic That Wasn’t

2013-07-16

In the recent past, people who are supposed to know have warned that there is going to be an explosion of disability and dementia cases in the near future.  This warning is based on an extrapolation of current rates of increased survival among the elderly, projections of increases in the population of elderly, and current rates of dementia among currently elderly people.

It turns out that rates of dementia among the elderly have been dropping.  A study quoted by the good old New York Times online found a 25% decrease in dementia incidence over the last two decades.  Further improvements are likely and it is unknown if there will be a ceiling on decreases in dementia incidence.  It is possible that dementia could be almost entirely avoided through-out one’s lifetime if the appropriate medical regimen is used.  The concept of dementia could become obsolete if someone develops a way to upload one’s memory into a computer.

This phenomenon, that is the averted epidemic of dementia with its fear about associated societal costs, is an example of mispredicting the future that deserves to be remarked upon.  The fallacy in reasoning that caused this fear of an epidemic is in thinking that current trends can be linearly extrapolated indefinitely into the future.  It is much more likely to see limits on current trends that prevent linear growth.  Even the phenomenon of sudden geometric increase or collapse is more commonly seen than indefinite linear growth.

Therefore, it is important to recognize constraints on the growth of a phenomenon and remember that dynamically changing environments are to be expected.  Committing to crash programs on the basis of limited evidence is as wrong as an approach of waiting until evidence is completely overwhelming before acting.

How positive does evidence have to be before action is taken, and how much effort is justified based on any given amount of evidence?

(As I have said before, there is already overwhelming evidence that humans are causing global carbon dioxide accumulation and worldwide warming.  There is also overwhelming evidence that this phenomenon will be bad for human beings.  There is also some good evidence that the planet will tolerate warming without much complaint.  How much action is justified in an attempt to avert this?  Probably a lot more than we’re seeing right now.)

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