Dec. 2, 2014 -- Guys, that ticking you hear might be your biological clock.
As women age, fertility wanes, and the risk of genetic problems in their babies increases. Now, a growing body of research suggests that middle-aged men might be more likely to father children with mental health problems, as well as rare genetic disorders, such as the most common type of dwarfism. The findings are mixed.
For example, a recent study of Swedes born between 1973 and 2001 found that those born to fathers 45 and older were more likely to have a variety of brain and nervous system conditions -- such as autism, bipolar disorder, schizophrenia, and ADHD -- because of an increase in mutations in older men’s sperm. Also, children of older fathers were more likely to get bad grades in school, do drugs, and attempt suicide.
But scientists stress that even if “advanced paternal age” -- a vague term that applies to men who father children at 45 or older -- doubles or triples the likelihood of a particular health problem in offspring, the actual risk is still quite low.
“It should be on their [men’s] radar, but it’s not recommended that people do anything crazy like freezing sperm or not having kids at those ages,” says Alan Brown, MD, MPH. He's a professor of psychiatry and epidemiology at Columbia University.
And yet, says fertility specialist Paul Turek, MD, perhaps a half-dozen healthy young men schedule appointments with him each year to discuss banking their sperm for use years or even decades down the road.
"I just had another one come in,” says Turek, who has offices in San Francisco and Los Angeles, and, in his mid-50s, has two daughters, ages 11 and 6. These young men are “planners. They want everything in order. They like insurance. They like to get everything in place for the future. The research tends to scare them.”
He says even after he points out to them that the research isn’t conclusive and that plenty of older men father healthy children, some still decide their peace of mind is worth the cost of banking their sperm -- about $500-$1,000 to open an account and $250-$500 a year thereafter.
‘Men Have Reproductive Aging’
U.S. sperm banks discourage donors who are 40 and older. Research suggests that sperm quality declines with age, although British scientists recently reported that the woman’s age appeared to be more of a factor than the sperm donor’s in achieving a pregnancy.
“I think that perhaps the bigger issue is, in the medical community, it isn’t always appreciated that men have reproductive aging as well,” says Dolores Lamb, PhD. She's the director of the laboratory for male reproductive research and testing at Baylor College of Medicine.
Some of the research about age-related decreases in the quality of sperm is controversial, Lamb says, “but if you look collectively at the data that’s been published, there seems to be some decline in total sperm count and some decrease in volume.”
That’s not totally surprising, she says, since testosterone levels gradually fall once men are past young adulthood. But “even though semen quality goes down a bit, the men largely are still fertile,” Lamb says.
In fact, the percentage of U.S. men fathering children in their 40s or early 50s has been growing, according to the National Center for Health Statistics. For men 40-44, the birth rate -- the number of men out of 1,000 who fathered a child -- has crept up every year since 1980. In 2012, the birth rate for that age group was 26.8, compared to 17.1 in 1980. For men 45-49, the 2012 birth rate was 8.6, up from 6.1 in 1980. And for men 50-54, the 2012 birth rate was 2.6, up from 2.1 in 1980. In case you’re wondering, the birth rate for men 55 and older has held pretty stable for more than 30 years at 0.3.
While women are born with all the eggs they’ll ever have, sperm are constantly turning over. That constant turnover increases the likelihood of spontaneous mutations. So while middle-aged men might not have much trouble fathering children, the extra mutations in their vintage sperm might help explain an increased risk of brain and nervous system problems and rare genetic conditions in their offspring.
One of the most attention-getting studies on this subject involved 78 Icelandic trios consisting of mother, father, and child. In a paper published in 2012 in Nature, the researchers reported that, on average, men had two mutations in their sperm each year. The scientists estimated that the number of new mutations in sperm doubled every 16 ½ years, leading them to conclude that the father’s age at conception, not the mother’s, was the main reason for new hereditary mutations in their children. Their findings raise the question of whether the reported increase in autism spectrum disorder diagnoses might at least partially stem from a rise in the average age of fathers at conception, the scientists concluded.
An extra couple of mutations in sperm every year is relatively insignificant, though, says Matt McGue, PhD. He's the co-director of the Minnesota Center for Twin and Family Research.
On the Plus Side
In an analysis of more than half a million Swedish males published last year in the American Journal of Epidemiology, researchers questioned whether “later" is better or worse when it comes to the relationship of parental age and children’s IQ. The team found no link between advanced paternal age and sons’ IQs.
Older fathers (and mothers) bring advantages to the table as well. They tend to be better-educated and earn more money than people who become parents in their teens or 20s.
As McGue says, “If I had an older father … I wouldn’t worry about it. There is such diversity in the age of parents today. Does it matter to kids? I don’t think it actually does.”