The effect of parental age on child development at 36 months: Insights from the Japan environment and children's study

The impact of parent-childbearing age on child development at 36 months of age is controversial. We used data from a large cohort study with multiple imputation and mediation analyses of variables. A total of 72,606 parent–child pairs from the Japan Environment and Children's Study were included in the study. Parents' ages were categorized into five groups. We used five domains of the Japanese translation of the Ages and Stages Questionnaire, Third Edition (J-ASQ-3). Scores below the cutoff value at 36 months were defined as developmental delays in each domain. We used three logistic analysis models. In Model 3, we analyzed maternal and paternal age using other variables and covariates. The outcome was a developmental delay in the five domains of J-ASQ-3. In Model 3, ORs for the developmental delay scores regarding parental age were significantly associated with all five domains of J-ASQ-3. The mediation analysis showed a significant mediation interaction effect for mothers but localized for fathers. Advanced paternal and maternal ages were associated with developmental delay in children. Awareness of the risks of childbearing at an advanced age is crucial. This manuscript used data from a large cohort study with multiple imputation and mediation analyses. With these analyses, we identified the pure effect of advanced parental age on their children’s development at 36 months. •Both advanced paternal and maternal ages were associated with developmental delay in children.•The effects of advanced maternal age on child developmental delay are similar to the paternal one.•Awareness of the risk of childbearing at an advanced parental age is crucial.