Excellent question, and I hope one that will be looked at, if it hasn't been already.
As I mentioned before to another poster, who had proffered a genetic link to autism, I suspect that there may be groups of people whom are more susceptible to the causes of autism-- even to the syndrome, itself.
There are plenty of afflictions out there that are more prevalent in men than women, women than men, blacks than whites, etc. Maybe hormone levels protect one somewhat? I've not a clue.
It is an important question, though.
http://www.danconference.com/index.htm
Defeat Autism Now
There are some very interesting findings coming out that indicate the children who do not have good pathways to rid their bodies of heavy metals are the ones who are susceptible to Autism from heavy metal exposure. They concentrate it in their tissues - gut, brain, etc. There have been some improvements in their disease by chelation and methyl-B12 injections. New book out by David Kirby:
Evidence of Harm : Mercury in Vaccines and the Autism Epidemic: A Medical Controversy
by David Kirby
True on 188. just like some can smoke and live long.