Differential genetic influence for components of memory in aging adult twins

Abstract

Objective: To investigate the relative proportion of genetic and environmental contributions to verbal memory in community-dwelling World War II veteran twins. Design: The California Verbal Learning Test (CVLT) was administered to 94 monozygotic (MZ) and 89 dizygotic (DZ) elderly male twin pair participants in the fourth examination of the National Heart, Lung, and Blood Institute Twin Study. Setting: Subjects voluntarily participated on an outpatient basis at a research or medical center facility in 1 of 4 sites in the United states. Participants: Subjects had a mean age of 71.8 years (SD, 2.9 years), a mean educational level of 13.6 years (SD, 2.8 years), and no history of stroke and/or a Mini-Mental State Examination score of 23 or greater. Main Outcome Measures: Twin pair similarity in performance on 4 factor analytically derived components of the CVLT measuring verbal learning and memory, response discrimination, learning strategy, and recognition memory. Results: The MZ intraclass correlation was significantly larger than the DZ correlation for verbal learning and memory (I