Bipolar Risk for Kids Born to Older Dads
Study Shows Age of Dad Is a Factor in Risk of Child Developing Bipolar Disorder
Greater Age Means More Mutations
The fact that paternal age appears to be a more important risk factor for bipolar disorder than maternal age suggests that genetic mutations in sperm may be to blame, Frans says.
Men add more mutations to the gene pool than women because their reproductive cells continue to divide throughout their lives. Women have only about 23 divisions in the cells that produce their eggs, and these divisions occur before birth, the researchers note.
More divisions mean more potential mutations or DNA damage that could be driving the increased risk for bipolar disorder and other genetically influenced mental disorders.
According to one analysis cited by the researchers, by the time a man reaches the age of 20 the cells that create sperm will have passed through 200 divisions. By age 40, about 660 divisions have occurred.
Male fertility expert Harry Fisch, MD, tells WebMD that researchers are only just beginning to understand the impact of paternal age on child health.
Fisch directs the Male Reproductive Center at New York-Presbyterian Hospital/Columbia University Medical Center. He is also the author of the book The Male Biological Clock.
"What we know probably represents just the tip of the iceberg," he says. "Until just a few years ago, there was not much research in this area. But it is important that we understand this because so many more men are having children later in life."