By the time they reach their 20s, sons born to older fathers
and those who were born to younger men score about the same on intelligence
tests, a new Danish study finds.
Whatever negative biological effects a father's age might have
on his child may be offset by the benefits of being raised by a better educated
and financially stable older father, researchers said. "Our results are
reassuring for older fathers," Liselotte Petersen, the study's lead
author, told Reuters Health in an email.
"Our finding is that any potentially deleterious
effects of older fathers on general cognitive ability, as young adults may be
counter-balanced," Petersen, an associate professor at Aarhus University
in Denmark, said.
Previous studies have suggested that the children of older
fathers are more likely to be diagnosed with autism and schizophrenia. That led
Petersen and her colleagues to suspect that the children of older fathers may
also have lower intelligence scores.
For the study, they used data collected from 169,009 men
born after 1955. The goal was to see if there were any differences in
intelligence related to how old their fathers were at the time of their birth.
The researchers used the participants' scores from the intelligence test that's
required for military service in Denmark. Each participant took the test when
he was about 20 years old.
The participants' average score was 42, which is about the
same as that of the general Danish population. Initially, it appeared that the
children born to teenagers or to fathers over age 35 scored lower on the
intelligence test, compared to the kids of fathers in their mid to late 20s. But
the difference disappeared when Petersen and her colleagues adjusted those
scores to account for the parents' education levels, the children's birth
order, the mother's age and the year the test was administered.
Children of teenage fathers, however, scored on average
about one point lower, compared to the kids of fathers aged 25 to 29. Small
changes in intelligence may impact people in subtle ways, the researchers write
in PLOS ONE. But that difference would be magnified if it were applied across
the entire population.
The new study, however, can't prove that a father's age will
directly impact his child's intelligence. Also, it's hard to compare the
intelligence scores used in this study to scores in previous research,
according to NYU Langone Medical Centre's Dr Dolores Malaspina, because the
intelligence test used is unique to Denmark. But, Malaspina, who has done
similar work but wasn't involved in the new study, wrote in an email that this
is a "compelling area of research".