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Finkel D, Pedersen NL, Plomin R, McClearn GE: Longitudinal and cross-sectional twin data on cognitive abilities in adulthood: The Swedish Adoption/Twin Study of Aging

Division of Social Sciences, Indiana University Southeast, New Albany 47150, USA.
Developmental Psychology (Impact Factor: 3.21). 12/1998; 34(6):1400-13. DOI: 10.1037//0012-1649.34.6.1400
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ABSTRACT Cross-sequential methods of analysis, designed to separate age and cohort effects, were applied to data from the Swedish Adoption/Twin Study of Aging. Thirteen cognitive variables were collected at 3 times of measurement separated by 3-year intervals. Data were available from 85 individuals from monozygotic (MZ) pairs reared apart, 132 from MZ pairs reared together, 207 from dizygotic (DZ) pairs reared apart, and 178 from DZ pairs reared together (age range at first assessment: 41-84 years). Time x Cohort interactions were found for mean performance on 8 of the measures, revealing stable mean performance in the younger cohorts and longitudinal decreases in mean performance in the older cohorts. Cohort and time effects for total variance were mixed; little evidence was found for increases in variance with age. Age changes and cohort differences in genetic and environmental components of variance were test-specific; several Cohort x Time interactions attained significance. Heritability of the general cognitive ability factor showed significant longitudinal decreases over time in the older cohorts.

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    • "Another possible factor is age of the participants. A recurrent pattern in studies covering a wider age range is namely that baseline age is negatively related to memory change (e.g., Colsher & Wallace, 1991; Finkel, Pedersen, Plomin, & McClearn, 1998; Zelinski et al., 1993). Thus, a possibility is that with passage of time, young/middle-aged groups remain relatively stable whereas older groups decline. "
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    • "However, the risk for MCI did not differ reliably between CC homozygotes and T carriers of the KIBRA gene, and this gene was not associated with memory performance among the MCI individuals, leading the authors to suggest that the KIBRA gene " plays all but a limited role after scores fall below a certain threshold " (Almeida et al., 2008, p. 1675). At a more general level, results from twin studies indicate that the genetic contribution to individual differences in cognitive functioning may decrease in very old age (Finkel et al., 1998). Thus, in line with the resource modulation hypothesis, there is initial evidence that the influence of common genetic polymorphisms may decrease in AD and in the terminal phase of the lifespan, when cognitive resources are greatly depleted. "
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    ABSTRACT: Individual differences in cognitive performance increase from early to late adulthood, likely reflecting influences of a multitude of factors. We hypothesize that losses in neurochemical and anatomical brain resources in normal aging modulate the effects of common genetic variations on cognitive functioning. Our hypothesis is based on the assumption that the function relating brain resources to cognition is nonlinear, so that genetic differences exert increasingly large effects on cognition as resources recede from high to medium levels in the course of aging. Direct empirical support for this hypothesis comes from a study by Nagel et al. (2008), who reported that the effects of the Catechol-O-Methyltransferase (COMT) gene on cognitive performance are magnified in old age and interacted with the Brain-Derived Neurotrophic Factor (BDNF) gene. We conclude that common genetic polymorphisms contribute to the increasing heterogeneity of cognitive functioning in old age. Extensions of the hypothesis to other polymorphisms are discussed. (150 of 150 words).
    Frontiers in Neuroscience 01/2009; 2(2):234-44. DOI:10.3389/neuro.01.039.2008 · 3.70 Impact Factor
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    • "Telomere length predicts survival, S. L. Bakaysa et al. © 2007 The Authors Journal compilation © Blackwell Publishing Ltd/Anatomical Society of Great Britain and Ireland 2007 2 Swedish twin pairs (McClearn et al ., 1997; Finkel et al ., 1998), using a co-twin analysis. The study design takes advantage of the fact that monozygotic (MZ) and dizygotic (DZ) twins share 100% and 50% of their (segregating) genes, respectively, and that twins reared together share the same environment during their formative years. "
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    ABSTRACT: Telomeres prevent the loss of coding genetic material during chromosomal replication. Previous research suggests that shorter telomere length may be associated with lower survival. Because genetic factors are important for individual differences in both telomere length and mortality, this association could reflect genetic or environmental pleiotropy rather than a direct biological effect of telomeres. We demonstrate through within-pair analyses of Swedish twins that telomere length at advanced age is a biomarker that predicts survival beyond the impact of early familial environment and genetic factors in common with telomere length and mortality. Twins with the shortest telomeres had a three times greater risk of death during the follow-up period than their co-twins with the longest telomere measurements [hazard ratio (RR) = 2.8, 95% confidence interval 1.1-7.3, P = 0.03].
    Aging cell 01/2008; 6(6):769-74. DOI:10.1111/j.1474-9726.2007.00340.x · 5.94 Impact Factor
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