Independent and dependent contributions of advanced maternal and paternal ages to autism risk.
Older moms steadily raise autism risk; older dads only add risk when moms are under 30.
01Research in Context
What this study did
Baker et al. (2010) looked at birth records for thousands of families. They asked: does mom’s age, dad’s age, or both raise the chance of autism?
They counted every case of autism and lined it up with how old each parent was at birth.
What they found
Mom’s age mattered all the time. The older the mother, the higher the autism risk, step by step.
Dad’s age only mattered when mom was under 30. If mom was 30 or older, dad’s age added almost no extra risk.
How this fits with other research
Puleo et al. (2012) dug deeper into dads. They found the dad-age link shows up mainly in girls with simplex autism. F et al. did not split by sex, so the 2012 paper extends the story.
Day-Watkins et al. (2014) shift the lens: older dads often show mild autism traits themselves. This hints that dad’s age and dad’s traits may both feed into risk, not just age alone.
Braam et al. (2018) point at mom’s body chemistry, showing low melatonin in mothers also raises odds. Together these papers paint a picture: both mom’s biology and dad’s biology can matter, but in different ways.
Why it matters
When you take a family history, note both parents’ ages at birth. If mom was young and dad was much older, flag the case for possible de-novo mutations. If mom was older, plan for early screening either way. These simple questions cost nothing and sharpen your clinical eye.
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02At a glance
03Original abstract
Reports on autism and parental age have yielded conflicting results on whether mothers, fathers, or both, contribute to increased risk. We analyzed restricted strata of parental age in a 10-year California birth cohort to determine the independent or dependent effect from each parent. Autism cases from California Department of Developmental Services records were linked to State birth files (1990-1999). Only singleton births with complete data on parental age and education were included (n=4,947,935, cases=12,159). In multivariate logistic regression models, advancing maternal age increased risk for autism monotonically regardless of the paternal age. Compared with mothers 25-29 years of age, the adjusted odds ratio (aOR) for mothers 40+ years was 1.51 (95% CI: 1.35-1.70), or compared with mothers <25 years of age, aOR=1.77 (95% CI, 1.56-2.00). In contrast, autism risk was associated with advancing paternal age primarily among mothers <30: aOR=1.59 (95% CI, 1.37-1.85) comparing fathers 40+ vs. 25-29 years of age. However, among mothers >30, the aOR was 1.13 (95% CI, 1.01-1.27) for fathers 40+ vs. 25-29 years of age, almost identical to the aOR for fathers <25 years. Based on the first examination of heterogeneity in parental age effects, it appears that women's risk for delivering a child who develops autism increases throughout their reproductive years whereas father's age confers increased risk for autism when mothers are <30, but has little effect when mothers are past age 30. We also calculated that the recent trend towards delayed childbearing contributed approximately a 4.6% increase in autism diagnoses in California over the decade.
Autism research : official journal of the International Society for Autism Research, 2010 · doi:10.1002/aur.116