A man’s infertility is, of course, one of the most taboo subjects in our culture. We avoid it like a root canal, as it can strike at a man’s sense of self, piercing his protective virile armor. Women grapple with erratic cycles, fickle ovaries, checking their calendars and fretting over drugs like Clomid and Ovidrel; but men, well . . . men are always up for the act of procreation, proverbial fountains of fecundity. Except when they’re not. While female infertility has spawned an entire industry devoted to helping older women conceive, we now know that a man’s age, too, can play a crucial role.
Testosterone levels decline slowly from the age of 30—roughly at the rate of one percent per year—impacting how fast and straight a man’s sperm swim. And as a man traverses his thirties, another, more sinister process kicks in, as an enzyme known as aromatase converts testosterone to estradiol, or estrogen. This explains, in part, why a man’s body softens during the decade—it’s quite literally becoming more feminine. As Dr. Harry Fisch, a professor of urology at the Weill Cornell Medical College and director of the Male Reproductive Center at New York Presbyterian Hospital in Manhattan, notes, a large pot belly and “man boobs” are tell-tale signs of deficient testosterone and lowered fertility.
There’s also the looming threat of DNA replication. A man’s spermatogonia—the primitive cells that develop into sperm—divide around 23 times each year after puberty; a 50-year-old man has undergone some 800 rounds of division. Each cell-split can cause random mutations in the DNA coiled inside the head of a thrashing, vigorous sperm—the risk of a single-gene mutation, for instance, is up to five times higher in a 45-year-old man than in a guy two decades his junior.
These tiny skips in the genetic alphabet can lead to incidences of serious disease. There’s a growing corpus of evidence that links older fathers and offspring with severe disorders, such as schizophrenia, bipolarity, and autism. Key studies in Australia and Israel have found that the chance of a 40-year-old man siring a schizophrenic child is around six to eight percent. And emerging data suggests that the children of older fathers score lower on I.Q. and other standardized tests.
That said, adolescent fatherhood also presents some problems. As Dr. Fisch notes, “we suspect that a sixteen-year-old’s sperm isn’t all that good.”
So is there a clear answer to the question, When should I become a father?
If you map out the regions of successful fatherhood on a bar graph—fertility, financial, and parenting skills—you’ll see a few overlaps. While parenting skills, which are best at age 45 and up, are well off the chart, the region best represented on the graph are ages 28 to 32.
There are plenty of contrary examples, of course. We all know men who sired children in their early twenties and have proven to be exemplary fathers. And there are plenty of older men whose toddlers are hale and hearty and developing normally. But as the science of male fertility unfolds—and as more men embrace the role of caretaker—it’s vital to spotlight the information that men should know in order to make the correct judgments for themselves and their loved ones.
Last November I celebrated two milestones: my forty-sixth birthday and my oldest son’s eighth. Afflicted with a neuromuscular disease called Spinal Muscular Atrophy (SMA), he’s cognitively normal but severely disabled—born with a lack of motor neurons, he’s virtually paralyzed, and relies on various machines to perform the basic tasks of breathing and feeding. (I should note that his condition has nothing to do with my age; it results from the fact that both my wife and I are carriers of this particular genetic defect.) A decade ago, his doctors would have told us he wouldn’t live to his second birthday. Fortunately, the techniques to treat his respiratory problems have improved; he’s now reached 400% life expectancy, largely because of the arduous medical care we give him, ably assisted by a team of skilled nurses, therapists, and clinicians. Each day with him opens up like a flower.
Could I have embraced fatherhood had I faced these challenges at the age of 28 or 32? I doubt it. At that age I was completely absorbed by the trappings of a profession, business lunches charged to expense accounts, hitting the bars with friends. The raucous rhythms of my young manhood seasoned me in ways that made want to be the best father possible—but that epiphany came later. For better and worse, the disease has become the organizing principle in my life, shaping my relationship with him and with my healthy, younger twins. In my early thirties I would have recoiled from the experience of extreme parenting; in my late thirties I took it up as a cause, hunkering down in my own solitary classroom of the mind, drilling myself in the basics, as though I were learning simple arithmetic and grammar all over.
Turns out 37 was the perfect age for me to become a father.