"Additionally, complete data on ApoE status, education level, ethnicity, dietary habits, and lifestyle choices were not available for all study participants, so none of these can presently be eliminated as contributory to the results observed."
Background on ApoE: http://en.wikipedia.org/wiki/Apolipoprotein_E#Alzheimer.27s_.... I'd be interested to see how participants' ApoE status relates to these results.