Researchers at the university identified 13,428 patients in Sweden with bipolar disorder in registers dating from the 1970s to 2001. Each patient was compared with a random sample of five “healthy controls” of the same age and sex.
After adjusting for the age of the mother, the researchers found that children whose fathers were over 29 years old at the time of the their birth ran a higher risk of being diagnosed as bipolar, a disorder previously referred to as manic depression.
Men aged 55 or older were 1.37 times as likely as men aged 20 to 24 to have children with bipolar disorder.
Lead researcher Emma Frans told The Local that the higher prevalence could be caused by the fact that “genetic alterations are more common in older men”.
“As men grow older, their germ cells continuously divide themselves and mutate,” said Frans.
Since woman are born with their full supply of eggs, DNA copy errors do not increase in number with maternal age, researchers said.
“We are the first to show this link,” said Frans.
Older paternal age has previously been associated with a higher risk of schizophrenia and autism.
The findings of the Karolinska researchers are published in the September issue of Archives of General Psychiatry.