Heritability of neurocognitive functioning in the elderly: evidence from an Italian twin study

Background: the genetic and environmental origins of individual differences in specific cognitive abilities in the elderly are poorly understood. One reason is the lack of studies performed in cohorts with normal cognitive functions. Objective: to estimate the relative contributions of genetic and environmental factors in determining inter-individual variation in neurocognitive abilities in the Italian population. Design: cross-sectional analysis of twin data. Setting: a sample of older twins with normal cognition from the population-based Italian Twin Registry (ITR). Subjects: twin pairs resident in Rome and born between 1926 and 1940, identified through the ITR in 2002. The final study population included 93 twin pairs. Methods: subjects underwent neuropsychological tests providing information about different cognitive domains. The contributions of genetic and environmental effects were assessed using standard univariate twin modelling based on linear structural equations. Results: the best-fitting model incorporated additive genetic (A) and unique environmental (E) sources of variance for th