From the Guidelines
Advanced paternal age is more strongly linked to an increased risk of autism in children, likely due to the increased chance of new genetic mutations in sperm cells. The relationship between parental age and autism risk is complex, with both higher paternal and maternal age being associated with an increased risk of autism in children. However, the most recent and highest quality study, 1, suggests that advanced paternal age (typically over 40 years) has a stronger association with autism risk. Some key points to consider include:
- Advanced paternal age increases de novo intra- and inter-genic germline mutations, sperm aneuploidy, structural chromosomal aberrations, sperm DNA fragmentation, birth defects, and genetically-mediated conditions, including autism, in the offspring.
- The risk of autism may be 1.5 to 2 times higher for fathers over 40 compared to fathers in their 20s.
- Advanced maternal age (typically over 35 years) is also associated with autism risk, though the relationship is somewhat less consistent across studies.
- The biological mechanisms likely differ between parents, with increased de novo mutations in sperm being the primary mechanism for fathers, and chromosomal abnormalities, pregnancy complications, or epigenetic factors being possible mechanisms for mothers. It's essential to understand that these are risk factors that slightly increase the likelihood of autism, not deterministic causes, and most children born to older parents do not develop autism, as noted in 1.
From the Research
Autism and Parental Age
- The relationship between autism and parental age has been investigated in several studies, with some suggesting a link between advanced parental age and increased risk of autism in offspring 2, 3.
- A study published in Molecular Psychiatry in 2011 found that offspring of men aged 50 years or older were 2.2 times more likely to have autism than offspring of men aged 29 years or younger, after controlling for maternal age and documented risk factors for autism 2.
- A meta-analysis published in Acta Psychiatrica Scandinavica in 2017 found that advanced parental age was associated with an increased risk of autism in offspring, with an 18% and 21% higher risk of autism for every 10-year increase in maternal and paternal age, respectively 3.
Maternal Age vs. Paternal Age
- Some studies suggest that advanced paternal age may be a stronger risk factor for autism than advanced maternal age 2, 3.
- However, a study published in Autism Research in 2020 found that younger paternal age (<30 years) was associated with increased odds of autism, and that increasing paternal age was associated with higher cognitive functioning in children at high familial risk for autism 4.
- The relationship between maternal age and autism risk is less clear, with some studies finding an association between advanced maternal age and increased risk of autism, while others have found no significant association 3, 4.
Mechanisms and Implications
- The mechanisms underlying the association between advanced parental age and autism risk are not fully understood, but may involve de novo mutations or epigenetic alterations associated with aging 2, 3.
- Further research is needed to understand the relationship between parental age and autism risk, and to inform genetic counseling and testing for families at risk of autism 5, 6.