Traditionally, research has focused on women's "biological clock." But in recent years, scientists have been looking more and more at how the father's age at conception might affect the baby, too. A study published Wednesday hints that age really might matter — in terms of the child's mental health.
Researchers from the University of Indiana and the Karolinska Institute found that compared with children fathered by men who were 20-24 years old, kids born to dads who were 45 or older were three times as likely to have autism and 13 times as likely to have ADHD. Kids born to older dads were also more likely to go on to develop substance abuse problems and get lower grades in school. The findings appear in JAMA Psychiatry.
To figure out how paternal age was related to children's psychiatric health, the researchers looked at millions of parents in Sweden who had children between 1973 and 2001. The researchers took into account the mother's age, as well as other demographic factors that might play a role in the child's cognitive development and mental health.
"There's a growing body of literature that suggests that advancing paternal age is associated with a host of problems," D'Onofrio tells Shots. Another study, published in JAMA Psychiatrylast month, found that the children of older fathers seemed to be at greater risk for developing schizophrenia and autism.
D'Onofrio and his colleagues paid special attention to siblings and cousins, and found that even among kids in the same extended family, a dad's age when his child was born made a difference.
The results are in line with a growing body of research linking older fatherhood with various developmental problems in children.
However, the study looks only at how paternal age and children's mental health are associated — it's a correlation, Reichenberg cautions, not a proven causal link. Scientists haven't yet determined the mechanisms of the effect. But it doesn't seem to be simply a matter of overdiagnosis among the children of older parents, the scientists say. Other research has found that as men get older, their sperm cells are more likely to contain random mutations that might, theoretically, contribute to disorders like autism in their kids.
Ultimately, men and women of all ages, he says, should remember that age is only one of many factors influencing the developing baby's health.
"The most important thing is [that] future mothers and fathers should still go ahead and have children, even if the father is older than 45 or 50," Reichenberg says. "Most of these children will be absolutely fine."