@farmerman,
The studies of this goes back at least to 2003, but i'll freely admit that i'm not sufficiently familiar with medical research abstracts to find the specific information to which you refer. I suspect that most of the information can be found on "the deep web." That is an area into which i don't know how to delve, except for some historical documents (which i can do because a former employer does not seem to have noticed that i'm still on an access list, so the less said about that, the better).