Methods and compositions for determining whether a subject will age without developing cognitive decline are provided. An exemplary method includes detecting one or more allelic variants in a gene encoding low density lipoprotein-related protein 1B. In a preferred embodiment, the detecting step is accomplished by contacting a sample obtained from the subject with a probe that forms a detectable complex with a nucleic acid in the sample containing an allelic variant indicative of aging without developing cognitive decline, wherein detection of the allelic variant in the sample indicates that the subject will age without developing cognitive decline.