the gwa study (the one in science) looked pretty solid to me. large effect, replication, tests for population stratification, plus functional studies = very convincing.

fyi, david goldstein at duke is also doing a gwa study of memory.

In regards to the APOE 4 allele, how did this effect work, and how sizable was it? I mean, the APOE 4 allele causes alzheimer's by way of some sort of disruption in the transportation of blood proteins I believe. So how would this factor into memory? Did they find an actual causational link, or was it just a vague correlate?

The APOE 4 allele is much quite more common in Africans than in whites and asians, oddly enough.