Oct. 25, 2001 -- That ticking sound you hear is your biological clock winding down. No, not you, ladies. Guys apparently have reproductive clocks of their own, according to research that suggests older-than-average dads are more likely to have children at risk for certain medical problems, including some cancers.
In the latest addition to this list, a new study has found that children of older fathers have a greater risk of developing schizophrenia, a devastating mental illness associated with hallucinations and delusions.
"Father's age is certainly as important -- and may be even more important -- than mother's age in terms of schizophrenia risk, and in terms of many birth defects as well," researcher Dolores Malaspina, MD, tells WebMD.
In fact, she says, it's been well recognized for many years that a child born to a father older than 40 has a 1 in 200 chance of having a genetic abnormality.
"The reason the public is not generally aware of this is because there is no genetic screening that can be done," says Malaspina, associate professor of clinical psychiatry at Columbia University and a research psychiatrist at New York State Psychiatric Institute, both in New York City.
Genetic diseases are caused when the genes from the mother, the father, or both get changed somehow when they're passed on to the baby. In general, it's easier to pinpoint the genetic errors that come from the mother, as they generally involve more of the chromosome and are therefore easier to detect on screening tests. In comparison, finding the much smaller genetic errors produced by the father is akin to looking for a needle in a haystack.
In their study, Malaspina and her colleagues reviewed the records of more than 87,000 people born in Jerusalem between 1964 and 1976 and linked them to the records kept at the Israel Ministry of Health. Their analysis demonstrated that men aged 45 to 49 were twice as likely to have a child who will suffer from schizophrenia later in life than men who became fathers while younger than 25.
The findings suggest "that at least some part of schizophrenia is caused by new [genetic] mutations," says James Crow, PhD, an expert on rates of genetic mutations as a function of a father's age.
After reviewing the study for WebMD, he says it furthers the case "that at least some part of schizophrenia is caused by new [genetic] mutations."
The older men get, the greater their risk of passing on genetic mutations, says Crow, professor emeritus of genetics at the University of Wisconsin, who reviewed the study for WebMD, probably because the number of times sperm-producing cells must duplicate also increases with age. The more duplications, the more chance there is for error.
Psychologist Enid Reed, PhD, has another interpretation.
The risk of genetic mutations increases with age, she agrees, but there are other risk factors associated with developing schizophrenia that the researchers might not have considered. For example, pregnant women who come down with the flu during their second trimester are also at increased risk of having a child who will eventually develop schizophrenia
So before you older men call off your baby plans, heed the advice of Malaspina and Crow.
"It's important for people to realize that most offspring of older fathers are perfectly fine," says Malaspina. "I would not want this to be interpreted that older fathers should not have children, but this does possibly suggest that when people are planning their families, they might consider the age of the father as well as the mother."
Furthermore, says Crow, the effect of age is not very large, and these findings are more relevant to the ongoing efforts being made to understand the cause of schizophrenia. This research is just one step more along the path of clarifying the role genes play in the development of the disease.