I recently posted some comments about urban asthma possibly arising from 
exposure to cockroaches.  Off-topic though it may be, I feel responsible for 
posting a fresh update.
A recent study of asthma in rural Scotland suggests that something else is at 
work.  Even on the Isle of Skye, which is pretty well pollution free (and 
probably cockroach free as well, although this wasn't specifically 
mentioned), asthma rates have increased dramatically.  The latest suspicion, 
and this is ONLY A SPECULATION, is that since there is a correlation with the 
number of times a family moves it might be exposure to different environments 
that somehow creates a susceptibility to asthma.
Meanwhile, another study suggests that childhood diseases protect against 
asthma: asthma rates seem to go up as vaccination becomes more common.  In 
particular, use of a tuberculosis vaccine in Japan correlates with an 
increase in asthma there.  Again, there is only a SPECULATION that exposure 
to tuberculosis alters the responses of the immune system.
The one thing that comes through loud and clear is that there is probably no 
one cause and possibly no one mechanism involved.
Jerry Schwartz
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