We agree with Edwards and Roff’s comment that their additional analyses do not allow the research community to reject the hypothesis that advanced paternal age is associated with inferior cognitive outcomes in the offspring.

We note that the addition of extra covariates to the models exploring the association between paternal age and offspring cognitive outcomes weakens the strength of the association in some but not all outcomes. We also found that the addition of extra (often highly inter-correlated) variables such as sibship order resulted in weakening of the pattern of association (Saha et al, 2009). We note that the additional analyses undertaken by Edwards and Roff continue to broadly support the original hypotheses (Table 4). For two of the outcomes (Bayley mental at age 8 months and Graham Ernhart at age 4), the hypothesized relationship is obvious on visual inspection (Figure 1).

In light of the consistent and understandable association between advanced maternal age and superior cognitive outcomes in the offspring, it is curious that both research teams have failed to identify comparable positive associations with respect to paternal age. The latest analyses reinforce the need for the research community to explore why the offspring of older fathers do not benefit in neurocognitive outcomes in the same manner as the offspring of older mothers.

John McGrath
Sukanta Saha
Adrian Barnett


Saha S, Barnett A, Foldi C, Burns T, Eyles D, Buka S, McGrath J, (2009) Advanced Paternal Age Is Associated With Impaired Neurocognitive Outcomes during Infancy and Childhood. PLoS Medicine ;6(3):e40. (on-line comment Post-hoc analyses related to birth order)