Re: cancer clusters

[RuthWeiner@AOL.COM]

Three comments on clusters:


Disclaimer:  I am not an epidemiiologist.


1.  Several years ago one of my M. S. students investigated "leukemia clusters" near industrial ponds in northwest Washington.  She could not show any association except geographical proximity: no consistent dose response, not even consistent exposure to the water or consistency in the duration of the geographic proximity.


2.  Two years ago, the New Yorker published an article on disease clusters by Malcolm Gladwell.  As I recall, the author stated that geographical clusters had not proved out in any case that he looked at.  Disease clusters seemed to be much more the result of common behavior  than of geographical location.


3.  I remember the study of spontaneous abortions in Alsea. Oregon, where it was claimed that the unusually high incidence was related to effluents from the local tree-spraying operations (spraying with pesticides).  It turned out that there was not an unusually high incidence of spontaneous abortion.


The epidemiology of AIDS, which did ultimately lead to elucidation of the cause of the disease, strikes me as a classic example of good epidemiology, particularly because it began with observation of a serious adverse effect -- a complex of fatal diseases -- and not with any preconceived notion about possible causative factors.






Ruth Weiner, Ph. D.

ruthweiner@aol.com