The effect of parental age on child development at 36 months: Insights from the Japan environment and children's study.
In a huge Japanese sample, every extra year of either parent’s age slightly raised the odds of developmental delay at age three.
01Research in Context
What this study did
Fukuda et al. (2024) tracked 72,000 Japanese babies from birth to 36 months. They used the ASQ-3, a quick parent checklist, to spot delays in five areas: talking, moving, self-care, social, and problem-solving.
Every extra year of mom or dad age was counted to see if it nudged up the odds of any delay.
What they found
Older moms and older dads each raised the chance of delay in all five areas. The effect was small but steady: one more birthday for either parent meant slightly higher odds of scoring in the caution zone on the ASQ-3.
How this fits with other research
Two earlier big cohorts seem to clash. Chou et al. (2007) saw no link between mom age and autism severity in a clinic sample. Robinson et al. (2011) also found no tie between parent age and mild autistic traits in the general population. Both look like contradictions, but they studied narrow groups—kids already diagnosed or only subclinical traits—while Tomofumi’s group scanned the whole toddler population for any delay.
Capio et al. (2013) in Finland is a close cousin. They showed older dads raised autism odds and older moms raised Asperger odds, foreshadowing the broader delay signal seen now.
Shire et al. (2022) adds a twist: when mom’s “biological clock” runs fast, babies score slightly lower on early cognitive tests. Tomofumi confirms that parent age matters, even when you stick to calendar years.
Why it matters
You can’t change a parent’s age, but you can use it as a gentle red flag. When intake shows mom or dad was 35-plus at birth, plan an extra ASQ-3 review at 24 or 30 months. If scores slip, start early intervention sooner rather than waiting for a formal diagnosis. Share the brief checklist with pediatricians so nothing is missed.
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02At a glance
03Original abstract
BACKGROUND: The impact of parent-childbearing age on child development at 36 months of age is controversial. AIMS: We used data from a large cohort study with multiple imputation and mediation analyses of variables. METHODS AND PROCEDURES: 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. OUTCOMES AND RESULTS: 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. CONCLUSION: Advanced paternal and maternal ages were associated with developmental delay in children. Awareness of the risks of childbearing at an advanced age is crucial. WHAT'S THE PAPER ADDS: 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.
Research in developmental disabilities, 2024 · doi:10.1016/j.ridd.2024.104741