This review discusses age-related magnification of genetic effects on cognition. Heritability studies show substantial genetic influences on cognitive performance and decline in old age. Genetic influences on cognition, brain structure, and brain function were observed to become stronger as people aged. Older carriers of disadvantageous genotypes exhibited exacerbated decline. The data support the resource-modulation hypothesis, which states that genetic effects are magnified in persons with constrained neural resources, such as older adults. However, given that the findings are not unequivocal, the authors discuss the need to address several factors that may resolve inconsistencies in the literature. These included gene–gene and gene–environment interactions, study populations, gene–environment correlations, and epigenetic mechanisms.
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Papenberg G, Lindenberger U, Bäckman L: Aging-related magnification of genetic effects on cognitive and brain integrity. Trends Cognitive Science [Epub ahead of print July 14, 2015; doi: 10.1016/j.tics.2015.06.008.]
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http://www.ncbi.nlm.nih.gov/pubmed/26187033