Brief report: parental age and the sex ratio in autism

J Autism Dev Disord. 2009 Oct;39(10):1487-92. doi: 10.1007/s10803-009-0755-y. Epub 2009 May 19.


The male-to-female (M:F) ratio for autism spectrum disorders (ASD), typically about 4:1, appears to decrease with increasing paternal age, but this relationship has not been systematically tested. With 393 ASD cases from families with two or more ASD cases, we categorized paternal age into five age groups (<30, 30-34, 35-39, 40-44, 45+) and found that the M:F ratio was significantly decreased with increasing paternal age groups and remained so after also adjusting for maternal age. No significant relationship between maternal age group and the M:F ratio was observed. This study suggests that the M:F ratio is reduced with increasing paternal age consistent with de novo genetic or genomic anomalies arising more frequently as men age and then conceive children.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Age Factors
  • Autistic Disorder / genetics*
  • Child
  • Child Development Disorders, Pervasive / genetics
  • Female
  • Humans
  • Male
  • Maternal Age*
  • Middle Aged
  • Parents
  • Paternal Age*
  • Sex Ratio
  • Young Adult