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Increased risk of bipolar disorder for children of older dads

02/09/2008

Children of older fathers have an increased risk of bipolar disorder, a new report has claimed.

The behavioural condition involving episodes of mania and depression is well-known but its causes are relatively unknown.

In a report published in the Archives of General Psychiatry today, researchers from the Karolinska Institutet in Sweden looked at 13,428 patients diagnosed with the disorder.

For each one, they randomly selected from the registers five controls who were the same sex and born the same year but did not have bipolar disorder.

And when looking at the two groups, the older a patient's father, the more likely there were to have bipolar disorder.

"After controlling for parity [number of children], maternal age, socioeconomic status and family history of psychotic disorders, the offspring of men 55 years and older were 1.37 times more likely to be diagnosed as having bipolar disorder than the offspring of men aged 20 to 24 years," the authors claim.

The children of older mothers were also at a higher risk but not to the same degree as fathers, it was found

"As men age, successive germ cell replications occur, and de novo [new, not passed from parent to offspring] mutations accumulate monotonously as a result of DNA copy errors," the authors added.

"Women are born with their full supply of eggs that have gone through only 23 replications, a number that does not change as they age. Therefore, DNA copy errors should not increase in number with maternal age. Consistent with this notion, we found smaller effects of increased maternal age on the risk of bipolar disorder in the offspring."