The Issue
Older Dads and their kids' IQ
The Facts
Would-be trophy wives, listen up. That rich geezer you're considering for a husband - if you actually found someone left with money these days - may not be the best choice to father your children. A recently released study in the online journal PLoS Medicine suggests for the first time ever that the offspring of older fathers may perform slightly less well on IQ tests and other measures of cognitive ability than those of younger Dads.
The PloS study analyzed data on 34,000 children tested at 8 months, 4 years and 7 years from around the U.S with fathers ranging in age from 14 to 66 years and mothers from 12 to 48 years. The difference in test scores was just a few points, but consistently showed up at every age the children were tested. The findings also come after a 2001 report in the Archives of General Psychiatry which hinted that children of men age 50 may have as much as triple the risk of schizophrenia. Earlier studies also suggest a link between older paternal age and the risk of autism. Researchers suspect that with age, sperm may start to mutate and deteriorate to the point where function is impaired.
Interestingly, the PLoS Medicine study also found that the kids of older mothers may actually perform higher on intelligence tests than children of younger moms. Meantime the primary risk of older Moms to her offspring seems to be Down's syndrome, something for which there is screening. Does this spell the end of spring/autumn unions?
Two doctors debate the issue: John McGrath, the study's lead author, MD and professor at the Queensland Brain Institute of the University of Queensland in Australia and Harry Fisch, author of The Male Biological Clock (Free Press; 2008) and Director of the Male Reproductive Center at New York Presbyterian Hospital, Columbia University Medical Center.
The Debate
Dr. McGrath:
"We're nowhere near making recommendations about when to marry and have children," says McGrath. "But in the past we worried about the age of the mother; now my study combined with earlier other ones on schizophrenia and autism suggest that Dad's age may play a role in children's development. Dad's age is now on the radar screen."
He continues: "I don't want to scare the population, and on an individual level my findings may be trivial. But what's worrisome is that if we shift the paternal age older in the population at large, we may see intelligence scores drop below a certain threshold and this can have consequences for education and health as a whole."
"In the past when researchers focused on the age of the mother, the question of the father's age was largely ignored. But the results of our study are startling. Children's cognitive development at all the ages we studied was slightly worse when the Dad was older than when he was younger. The effect of a mother's went in the exact opposite direction."
McGrath adds that when the researchers looked at other factors, such as the economic and education levels of the parents, the gap in test scores between older and younger Dad's was somewhat offset. "But," says he, "I'm interested in the brain and it looks like there may be something going wrong in the brain of the offspring of older Dads. We must study this more."
Dr. Fisch:
"There's no question that that as men get older there's more incidence of genetic problems with their sperm and this might effect their offspring, but it doesn't mean that a child to an older father will have problems, just like it doesn't mean that if you're obese, you'll have diabetes."
"Also McGrath's study looked at the cognitive abilities of young children. You don't really know what the final cognitive function will be. It can be misleading when you test young kids. These things can change."
"That said," adds Fisch, "Women are blamed for everything. Now it's equal."
"If I were going to give advice to my kids, and if they had a choice, I would say try to have kids when you're younger rather than older. But life intervenes. Don't rush into something if you haven't met the right partner."
"What should an older man do? If someone is 50 and wants kids for the first time, he has to reverse the biological clock. We have found that there is a direct correlation between waist-size and testosterone. Belly fat is associated with lower testosterone which can affect sperm function. So the first step for healthy sperm is to stay in shape."
In addition, Fisch suggests that men "avoid recreational drugs like marijuana and the heat of Jacuzzis which can harm sperm for up to three months. Also don't smoke. Cigarette smoke can damage sperm and foods with phytoestrogens like tofu and miso soup should be avoided, too. If you're not trying to have a baby, then can eat all the miso soup you want, but if you're worried about your sperm don't."
"The point is, your chronological age may be one thing, but your biological age can be another. If you're a big, fat guy smoking cigarettes and drinking beer and you're older than 50, maybe your sperm is being harmed. They can be made healthier by changing your habits."