Education as direct and main cause of health?

Greg Mankiw has posted a link to an NYTimes article about a paper that claims that education is the single largest determinating factor in a person's health. I have linked to the original paper to which the article refers (see right). I haven't read much of it yet, but I hope to comment more later. At this point I'm wondering if the data this paper used (from the 1910s to the 1930s) is really robust at pinpointing a good causal relationship. .... I'll know more soon.