Paternal age effect

The paternal age effect is the statistical relationship between the father's age at conception and biological effects on the child. Such effects can relate to birthweight, congenital disorders, life expectancy and psychological outcomes. The effect of paternal age on a trait can be measured as the causal correlation of paternal age on that trait. This is done by regressing paternal age onto the trait with important covariates controlled for. Typically, these covariates are father's trait phenotype, maternal age, birth order, and participant age (since older people had younger fathers on average, any generational trend would correlate with paternal age without age controlled for).

The magnitude of a paternal age effect on a trait is important in models of mutational pressure, where mutations tend to shift polygenic traits in one direction on average. This is because the causal correlation of paternal age on a trait reflects the effect of expected mutational load on that trait, since men accumulate de novo mutations in their gametes at a rate of about 2 per gamete per year.