Negative Effects of Paternal Age on Children's Neurocognitive Outcomes Can Be Explained by Maternal Education and Number of Siblings

Abstract

BackgroundRecent findings suggest advanced paternal age may be associated with impaired child outcomes, in particular, neurocognitive skills. Such patterns are worrisome given relatively universal trends in advanced countries toward delayed nuptiality and fertility. But nature and nurture are both important for child outcomes, and it is important to control for both when drawing inferences about either pathway.Methods and FindingsWe examined cross-sectional patterns in six developmental outcome measures among children in the U.S. Collaborative Perinatal Project (n = 31,346). Many of these outcomes at 8 mo, 4 y, and 7 y of age (Bayley scales, Stanford Binet Intelligence Scale, Graham-Ernhart Block Sort Test, Wechsler Intelligence Scale for Children, Wide Range Achievement Test) are negatively correlated with paternal age when important family characteristics such as maternal education and number of siblings are not included as covariates. But controlling for family characteristics in general and mother's education in particular renders the effect of paternal age statistically insignificant for most developmental measures.ConclusionsAssortative mating produces interesting relationships between maternal and paternal characteristics that can inject spurious correlation into observational studies via omitted variable bias. Controlling for both nature and nurture reveals little residual evidence of a link between child neurocognitive outcomes and paternal age in these data. Results suggest that benefits associated with the upward trend in maternal education may offset any negative effects of advancing paternal age.

Paternal Age and General Cognitive Ability—A Cross Sectional Study of Danish Male Conscripts

“…The finding of no impairment in offspring of older fathers in the adjusted model is consistent with the most recent studies [18-20]. In contrast, the negative impact of being the offspring of a teenage father persisted in the full model, and is consistent with the findings from the Israeli conscript study [16], the Swedish school performance study [19] and the Swedish conscript [20].…”

“…For example, a study among Israeli conscripts (male and female, age 16-17 years, n = 44,175) found an inverse U-shaped association between paternal age and intelligence scores [16]. Studies based on a large US birth cohort (samples 20,000 to 30,000) suggested that offspring of older fathers have impaired performance on various neurocognitive measures at age 8 months, 4 and 7 years [17], however, this association was attenuated by adjustment for sibship size [18]. …”

“…When comparing brothers, and adjusting for potential confounding variables (birth order, age at testing, conscription centre, year of testing) the effect of paternal age on intelligence was attenuated. Studies have also reported that the association between maternal age and cognitive outcomes in young adults is an inverted U-shape [16,20], whereas the studies that have examined neurocognitive measures in childhood report that the children of older mothers tend to perform better [17,18]. …”

Academic performance of opposite-sex and same-sex twins in adolescence: A Danish national cohort study

“…A previous Danish study comparing academic performance between twins and singletons born 1986 –1988 confirmed a number of potential confounding factors, including parental age and education (Christensen et al, 2006). Evidence suggests that parental age may influence cognitive ability of offspring (Edwards and Roff, 2010; Malaspina et al, 2005; Saha et al, 2009) and that parental education, a surrogate of socioeconomic status, is associated with offspring academic performance as well (Sirin, 2005). In this study, we showed that higher parental age and education were associated with higher academic achievement in both sexes (Supplementary Tables 1 and 2), and that parents of OS twins were older on average and had slightly higher education than the parents of SS twins (Table 1).…”

Sex differences in abnormal white matter development associated with conduct disorder in children

“…This was included because it is robustly associated with the child’s tested intelligence (Edwards and Roff, 2010; Bornstein et al, 2013; Ghassabian et al, 2014). The FSL function RANDOMISE (Winkler et al, 2014) was used to perform non-parametric statistical analyses, in which 5000 permutations were conducted to estimate the actual null distribution for comparison to obtained test statistics for significant positive and negative effects of each predictor variable.…”