Bipolar Disorder Tied to Age of Fathers (This is where new autism, bipolar, and schizophrenia comes from)

Bipolar Disorder Tied to Age of Fathers
By NICHOLAS BAKALAR
Published: September 8, 2008
The older a man is, the more likely he is to father children who develop bipolar disorder as adults, a large Swedish study reports.


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Get Health News From The New York Times » Previous studies have found an association between paternal age and both autism and schizophrenia, but this is the first time a connection with bipolar illness has been suggested. The study appears in the September issue of The Archives of General Psychiatry.

The researchers examined highly accurate Swedish government health records of more than seven million people with known biological parents to find 13,428 with bipolar disorder diagnosed at two or more separate hospital admissions. They matched each case with five controls, people of the same age and sex but without bipolar illness. They divided the fathers into five-year age categories beginning at 20.

After statistically adjusting for the age of the mother, family history of psychotic disorders, education level and other factors, they found consistently increasing risk as fathers aged. The highest risk was in fathers 55 and older. For mothers, after adjusting for the father’s age, they found a statistically significant increase in only the 35 to 39 age group.

“It’s a strong study from a methodological standpoint,” said Dr. Alan Brown, an associate professor of psychiatry at Columbia who was not involved in the study. “National registries are very important because you’re less likely to get bias and you can generalize findings across a whole country.”

David Glahn, an associate professor of psychiatry at Yale, also uninvolved in the work, agreed. “The methodology is very strong,” he said. “The statistics done here are all first-rate.”

There is a possible biological explanation for the phenomenon, the authors write. The older a man is, the more often his sperm cells have replicated, and the more replications, the greater the chance for DNA copying errors. These are random changes, called de novo mutations, that are not inherited. Women are born with a complete supply of eggs that do not replicate as they age. The finding of only a small effect of mother’s age on the incidence of bipolar illness in the offspring is consistent with this idea.

Emma M. Frans, a doctoral student in epidemiology at the Karolinska Institute and the lead author of the study, said in a phone interview that the findings applied to adult offspring only, not children. Bipolar illness is a rare disease in any age group; in community samples the prevalence varies from 0.4 percent to 1.6 percent of the population. Still, the risk of bipolar disease in the offspring of the oldest fathers was 35 percent higher than for those of the youngest, and the association was even stronger in the small number of cases in the study diagnosed before age 20.

Dr. Dolores Malaspina, a professor of psychiatry at New York University who has studied schizophrenia in the offspring of older fathers, called the new study “very important,” but added: “The vast majority of children of any fathers will not get bipolar illness. At the level of the whole population, it may be important, but for the individual father it’s a small risk.”

The Well column returns next week. Tara Parker-Pope’s blog is online: nytimes.com/well.