In the last few decades, the markets for Grecian Formula and baby formula have increasingly overlapped.
And while much research has focused on the effects of “advanced maternal age” on fertility and the health of offspring, men who father children in middle age have come under growing scientific scrutiny lately.
Many of the studies were conducted in Nordic countries, which keep detailed records of such information as the age of a newborn’s parents. Among the more recent findings:
- A study published last month of more than 2.6 million Swedes born between 1973 and 2001 concluded that the older their fathers were when they were born, the greater their risk of a variety of psychiatric conditions, such as attention deficit hyperactivity disorder, autism and poor academic performance.
- A study of Icelanders found that a father’s age, not a mother’s age, at the time a child was conceived is the single biggest reason for new hereditary mutations in offspring. The researchers suspect that the increasing age of fathers might explain the rise in children with autism spectrum disorders.
- A study of 169,000 Danish servicemen found that sons of teen fathers tended to score lower on IQ tests; those of men over 40 when they were born didn't, after accounting for factors like maternal age and parents’ education.
However, there’s no need to panic if you’re one of those dads who’ll be in his 60s when his kid graduates high school, scientists say.
“Most kids born to older fathers are not going to have psychiatric problems,” says Dr. Brian D’Onofrio, lead author of the Swedish study and a clinical psychologist at Indiana University.
Complex Effects of Parental Age
As the Danish study suggests, having older parents has its advantages, such as a higher household income, which could minimize the impact of a possibly higher rate of new mutations in older sperm.
“Looking at psychiatric disorders as one group, advanced paternal age is a risk factor,” says Liselotte Petersen, a co-author of the Danish servicemen study and a statistician at the National Centre for Integrated Register-Based Research at Aarhus University in Denmark. “However, it seems having a teenage mother or father increases risk even more.”
The impact of parents’ age on their offsprings’ health is far from black and white, says Dr. Kari Stefansson, chief executive of deCODE Genetics in Reykjavik, Iceland and co-author of the study of Icelanders.
“We are just finishing a manuscript that basically takes the age of the parents at the time the children were born and asks the question: What impact does it have on the fate of the children in general?” says Stefansson, a neurologist. “The story is fairly complex.”
The U.S. birth rate for fathers in their 40s has crept up from 23.2 per 1,000 men in 1980 to 34.7 per 1,000 in 2011, according to the National Center for Health Statistics. During that period, the birth rate for men 50 and older remained fairly stable at about 2.5 per 1,000 men.
Raising children is still generally a younger man’s game, with the highest birth rate — 102.2 births per 1,000 men — in men 30 to 34 in 2011, the most recent year for which data are available. Even that represents an upward age shift from 1980, though, when the highest birth rate was among men 25 to 29.
“We know that fathers who delay childbearing are different from fathers who have children when they’re younger,” D’Onofrio says, noting, for example, that older first-time fathers tend to be better-educated.
And, of course, some men father children when they’re in their 20s or 30s and when they’re in their 40s. D’Onofrio and his co-authors found a higher risk of psychiatric disorders and poor school performance in such men’s younger children than in their older children. The differences seen between younger and older siblings suggest that the impact of paternal age on their offspring’s fate is not due to inherent differences in men who delay fatherhood, D’Onofrio says.
(MORE: Your Childhood is Crucial to How You'll Age)
No Best Time
After Stefansson’s study appeared on the cover of the journal Nature in August 2012, one biologist speculated that if the findings could be replicated, it might not be a bad idea for young men to freeze sperm to be used when they’re ready to become fathers.
The research isn’t there yet, though, D’Onofrio says. “There’s no definitive study in my field,” he says. “I don’t think that we have enough scientific evidence to start making those recommendations based on this.”
For now, Petersen says, “I don’t think we have enough evidence to point to an optimal time to have children.”
Rita Rubin is a former USA Today medical writer who now writes about health and science for publications including Next Avenue, WebMD and NBCNews.com.