I read an article about this once, it concluded that it couldn't be determined if either people of atheist bents would gravitate towards certain careers or that certain careers created a more atheist friendly environment due to their nature - so those of beleif would end up atheist within them.
Its like palliative care nursing. I've met a lot of PRNs and none of them were true atheists, they all had some kind of beleif, whether mainstream or just a "spiritualism". Yet, with that said, I've met a lot of RNs who are atheists, I work with several. I actually want to do a research assignment on it, with the intention of seeing how best to serve nurses in these fields.
But I'd say people who are science minded, tend to be very critical and demanding of evidence, they go into a science career and find that there's no "evidence" for God and are surrounded by atheists who have concluded since there's no "evidence" there's no God. Of course, they fail to understand the nature of theology vs. science and evidence within those contexts.
The other consideration is are people now more likely to be "out" as atheists? I know people who are atheists on the inside but practice the faith to appease friends and family and their social circle.
Granted, modern atheists, like Dawkins et al, are really just a pack of angry idiots. They may be smart when it comes to science, but commenting on philosophy and theology they are not qualified to do so. I'm not going to go around writing books on quantum mechanics because I watched a few episodes of Star Trek. So, that angry almost "counter-the-man" indivdualism found in modern atheist thought speaks to a lot of people and personality types. Most of the Catholics/Christians turned atheists were such. Wanting to rebell against parents and society, so chose atheism to do it.
Basically I think its too broad a topic to peg it down as one variable. I think its a bunch of stuff that merges into a big cake of ignorance and chocolate icing.