Life Expectancy in Kerala

[js_dukelow@ccmail.pnl.gov]

David Walland <David.Walland@bristol.ac.uk> wrote:
Subject: Re: Kerala Downs Syndrome

> May I ask what is the normal life expectancy in Kerala?  This may have a
> bearing on the lack of expression of
> carcinoma.
> David Walland
> University of Bristol (UK)
> David.Walland@bristol.ac.uk

It is reasonable to suppose that a high mortality rate, causing early 
deaths from causes other than cancer, might tend to mask the carcinogenic 
effect of the high background radiation in Kerala. 

Something I stumbled onto a couple of months ago suggests the actual effect 
might be just the opposite. 

I discovered an interesting Note by E.E. Pochin, "Problems Involved in 
Detecting Increased Malignancy Rates in Area of High Natural Radiation 
Background", Health Physics, v. 31, pp. 148-151, August 1976.  

Pochin establishes that if cancer incidence or mortality data is age-
censored (using an appropriately chosen censoring age), then the sample 
size required for a specified statistical power is a factor of 5-15 smaller 
than the sample sized required with no censoring.  If the censoring age is 
35, then only cancer deaths (or incidence) occuring before age 35 in the 
experimental and control groups are counted and analyzed.  The intuitive 
reason for the smaller required sample size for age-censored data is that 
the statistical noise induced by the age-dependence of cancer incidence and 
mortality is minimized (i.e., "natural" rates (that is, non-radiogenic) 
increase steadily and, I believe, exponentially with age). 

What this seems to say is that, if low normal life expectancy in Kerala 
effectively "censored" the data on cancer incidence and/or cancer 
mortality, then the effect would be not the masking of any carcinogenic 
effect of radiation, but rather a revealing of that effect, because much of 
the noise from end-of-life "natural" cancers is missing from the data. 

One other thing: I seem to remember reading that many years of left-wing 
administration of the state government in the state of Kerala, with 
concomitant emphasis on social programs, have left Kerala with somewhat 
better health, education, and welfare statistics that the rest of India.  

Best regards.

Jim Dukelow
Pacific Northwest National Laboratory
Richland, WA

js_dukelow@pnl.gov

"The ideas expressed above are mine, and not my employer's."