Longitudinal memory performance during normal aging: twin association models of APOE and other Alzheimer candidate genes.

The APOE gene (apolipoprotein E) is a major risk factor for Alzheimer's Disease (AD) but has been inconsistently associated with memory in nondemented adults. Two other genes with mixed support as genetic risk factors for AD, A2M (alpha-2-macroglobulin) and LRP (low-density lipoprotein receptor-related protein), have not been studied in relation to memory among nondemented adults. The present study examined these three genes and latent growth parameters estimated from memory performance spanning 13 years in 478 twins from the Swedish Adoption/Twin Study of Aging (SATSA). APOE was associated with working and recall memory ability levels and working memory rate of change, with e4 homozygotes exhibiting the worst performance at all ages. Homozygotes for the rare A2M insertion/deletion variant exhibited accelerating decline on delayed figural recognition. There were no significant findings for LRP. Dominance, often untested in previous studies, was important in the current study's findings.