Advancing paternal age risks bipolar disorder

Babies whose fathers are older than 55 years of age face a significantly increased risk for bipolar disorder, an extensive study has shown.

Despite robust evidence supporting an association between increasing paternal age and severe mental disorders, including schizophrenia and autism spectrum disorder, the researchers believe no previous trials have looked at the association between paternal age and bipolar disorder.

They analyzed information on 13,428 patients with bipolar disorder and their parents by linking data from the Swedish Multigenerational Register and the Hospital Discharge Register.

Five healthy control individuals, matched for gender and year of birth to the case patients, were also studied.

Overall, 68 (0.5 percent) of the patients had fathers aged at least 55 years.

Analysis showed that, after adjusting for parity, maternal age, socioeconomic status, and family history of psychotic disorders, these offspring had a 37 percent increased risk for bipolar disorder (odds ratio [OR] = 1.37), compared with children whose fathers were aged 20-24 years when they were conceived.

The association between paternal age and bipolar disorder was much stronger for early-onset cases (OR = 2.63), Emma Frans (Karolinska Institutet, Stockholm, Sweden) and co-workers report.

Increasing maternal age also showed an association with the incidence of bipolar disorder, but the effect "was less pronounced," say the researchers.

"The results are consistent with the hypothesis that advancing paternal age increases the risk for de novo mutations in susceptibility genes for neurodevelopmental disorders," they conclude.

Source: Archives of General Psychiatry 2008; 65: 1034-40