Monday, January 14, 2008

The older you get the longer you live

The older you get, the older you will be when you die

For example, with average expectation of life I will die at 84. A newborn baby girl today can 'expect' to die before she is 82

This is not because of any increase in mortality due to rising obesity etc. Far from it. Expectation of life, in the statistical actuarial sense, depends on the assumption that mortality rates will stay exactly the same, age for age

It is because I have not been one of those unfortunate to die before I could draw my pension that my age at death can be expected to be higher than hers. The baby girls expectation of life takes account of the fact that some of her contemporaries will not be so lucky. Her 'expectation' of life is the average for all those born in the same year as she

I was pondering this because of a widely reported study that 'proves' a very significant extension to the lives of those who eat well, exercise, drink alcohol in moderation etc. I have heard only a report on the radio about it, have not had chance actually to look at the methodology, but the person talking about it (a scientist or doctor) appeared to be claiming that on average the goodie 2 shoes get an extra 14 years on average.

But the study lasted for only 11 years. So the extra years can only have been calculated by looking at age of death. And, by definition, many of those who died at older ages during the study period must have been older at the start of the study

Unless the results were corrected for this, the 14 years must just be an artefact, not a real effect