To test this hypothesis, we investigated the associations between APOE genotype, serum PlsEtn levels, and serum lipids, such as HDL, on cognition and odds of AD in a well-characterized community-based group of 1205 elderly persons enrolled in the Religious Orders Study (ROS) [27] or Rush Memory and Aging Project (MAP) [28]. The gene discussed is APOE; the disease is Alzheimer disease.