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The study analyzed a cohort born during the period 1959 to 1965 with cognitive measures collected at 8m, 4y, and 8y. The use of a cohort of that era reduces the influence of confounding factors like assisted reproductive technology, divorce, and complex stepfamily structure.
In contrast to the adverse effect of advanced paternal age is the superior performance on cognitive tests conferred to children of older mothers. Both of these age-related effects were reduced but not eliminated after controlling for socioeconomic factors like race, income, and education, or for parental mental health.