Previous studies have reported the association between advanced paternal age at birth and the risk of autistic-spectrum disorder in offspring, including offspring with intellectual disability.

To test whether an association between advanced paternal age at birth is found in offspring with high-functioning autistic-spectrum disorder (i.e. offspring without intellectual disability).

A case–control study was conducted in Japan. The participants consisted of individuals with full-scale IQ ⩾ 70, with a DSM–IV autistic disorder or related diagnosis. Unrelated healthy volunteers were recruited as controls. Parental ages were divided into tertiles (i.e. three age classes). Odds ratios and 95% confidence intervals were estimated using logistic regression analyses, with an adjustment for age, gender and birth order.

Eighty-four individuals with autistic-spectrum disorder but without intellectual disability and 208 healthy controls were enrolled. Increased paternal, but not maternal, age was associated with an elevated risk of high-functioning autistic-spectrum disorder. A one-level advance in paternal age class corresponded to a 1.8-fold increase in risk, after adjustment for covariates.

Advanced paternal age is associated with an increased risk for high-functioning autistic-spectrum disorder.