A Child's IQ May Be Affected By Paternal Age

The waiting game—to have children at an older age—may have some unintended and unwanted consequences. Having a baby sooner, for men, rather than later can make a difference in your child's IQ. While there are factors that may interfere with having children at the most opportune ages, such as not having a partner, fertility problems, not having the funds, or not being emotionally and mentally ready for a child, there seems to be some setbacks for men who are older when they have children.

For some couples, starting a family in their twenties or thirties isn’t possible for one reason or another. In today’s world, it actually seems there is a growing number of  young adults graduating high school and going on to college, focusing more on their careers than a family, and many couples are opting to start a family later in life, especially compared to earlier generations. Being educated helps couples to provide better lives for a family, and waiting to be truly ready for the responsibility of a family is very important. However, there seems to be evidence that fathers who wait until later in life to have children, run a risk of their children having slightly lower IQs than those born to younger fathers.

John McGrath at the University of Queensland, Australia, and colleagues recently released results of their study where they studied results on cognitive tests for more than 33,000 children born between 1959 and 1965 at ages 8 months, 4 years, and 7 years. He said, "Folk wisdom tells us that the offspring of older parents should get better opportunities and better nurturing." But he said, "That is exactly what we find for mothers—but exactly what we don't find for dads, which is startling."

McGrath and team used data from pregnant women recruited during the U.S. Collaborative Perinatal Project, with dad’s average ages ranging from 14 to 66, with the average being 28.4 and the mother's ages ranging from 12 to 48, and averaging 24.8. They found children with older fathers scored lower on a collection of tests when evaluating a child’s skills, such as concentration, learning, speaking, reading, arithmetic, memory, and motor skills.

For the study recently published in PLoS Medicine, the researchers looked into the link between a father's age, mother's age, and also considered socioeconomic factors, such as family wealth and parent’s education level. When considering factors such as parents’ income and education levels, the effect of both parent’s ages were adjusted on the results of the IQ tests.  Before any adjustment was made to consider wealth of a family and parent’s education, the Stanford Binet Intelligence Scale resulted in tests that were 6 points lower, on average, for  children born to fathers age 50, compared to those born to fathers age 20. When socioeconomic factors were considered the gap in test results dropped to only 2.2 points with the children of the younger fathers still scoring higher. The results showed that with older mothers, children scored higher on thinking skills test. Some feel this could be because mothers seem to become more nurturing as they age.

In previous studies, there have been links made between older fathers and certain health problems, such as birth defects, autism, and schizophrenia, which leads many scientist and doctors to recommend having children earlier in life, and with the newly released study showing lower IQ’s there may be new ammunition to speed up family plans. However, McGrath notes, "The significance of the effect linking paternal age and child cognition is small compared to many other socio-cultural factors—for example good prenatal nutrition, good nutrition for the offspring, good education, nurturing home life, excellent teaching and school opportunities [and so on]."

According to researchers men’s testosterone levels begin to decline slowly at age 30, and the ideal age for having children is in the 20s and early 30s. However, many times this target isn’t always possible due to certain factors. Alan E. Kazdin, a professor of psychology and child psychiatry at Yale noted that the study only followed children through the age of 7 and the findings didn’t look into what happened to the children age they aged. The study also considered older generations. There may need to be new research using children of today and see if the same result occurs.

While the new study suggests that a fathers age may cause a child to have a lower IQ than those children born to younger fathers, McGraw says, "I don't think we have enough evidence to say that fathers should avoid parenthood after a certain age," he says, "but I think we do need to educate people that there are risks they didn't know about.”