In a previous blog post, I summarized medical research showing that male fertility declines rapidly after age 35, while sperm abnormalities, birth defects, and mental disorders rise with paternal age. Most of the studies upon which these conclusions were drawn compared children born to unrelated families.
One concern about this body of research is that younger dads may differ from older dads along a host of socioeconomic and other relevant factors. But a more recent study published yesterday (February 26, 2014) in the Journal of the American Medical Association-Psychiatry put those concerns to rest: The researchers looked at siblings born to the same father and found the same clear pattern of increased risk with increasing paternal age.
The study was conducted by a research team led by Dr. Brian D'Onofrio of Indiana University in conjunction with researchers in Sweden. The team analyzed medical and public records of about 2.6 million people born in Sweden from 1973 to 2001. Sweden, like many European countries, has centralized medical care and keeps detailed records. This made it easy to verify the father’s age at the birth of each of his children, and to track each child’s medical history over time.
The results were startling: Compared with the children of fathers aged 20 to 24, children born to men age 45 and older had about twice the risk of developing psychosis, more than three times the risk of autism, about 13 times the risk of having attention deficit disorder, and a higher incidence of academic difficulties and substance abuse.
The researchers did not treat these findings likely. In fact, in an interview, Dr. D'Onofrio said, “We spent months trying to make the findings go away, looking at the mother’s age, at psychiatric history, doing sub-analyses. They wouldn’t go away.” The researchers controlled for every conceivable factor, including mother's age, parents’ education, and family income. But the risk associated with paternal age remained.
Why the greater risk? The most likely explanation lies in the pronounced increase in sperm abnormalities—genetic mutations--in older men. A man's sperm supply replenishes continuously throughout his lifetime. But, as the researchers pointed out, each time new sperm are created, there is a risk that an error may occur. Over time, this repeated reproduction of sperm cells lead to the accumulation of random errors, called de novo mutations. Most of these errors are harmless, but some lead to an increased risk in the disorders described here.
The difficulty, of course, is that the ideal age for healthy male and female reproduction (age 24-34) exactly overlaps with the ideal age for building one's career. As more couples delay childbearing in order to secure their careers, the incidence of autism, ADHD, and other disorders has risen. But having children at a younger age—prior to finishing one's education or securing one's career—can spell doom for a family's future financial security and welfare.
Young couples, armed with this knowledge, should keep this in mind as discussions concerning workplace reform begin to take center stage in political and business venues. They should not be placed between a rock and a hard place, forced to make a "Sophie's choice" between a healthy career and a healthy family. One solution is stop the implicit (and sometimes explicit) practice of permanently side-tracking employees for making "lateral moves" (to use AnnMarie Slaughter's term) into less demanding positions when their children are young, or downgrading job applicants as "not serious about their career" for taking time off for family formation. It is rarely the case that the skills and knowledge such workers possess become obsolete after a mere five or six years. Many other solutions have been proffered, and many more undoubtedly will be. But it is far too important an issue to simply dismiss as a "private matter" rather than one of public health and business policy.
Copyright Dr. Denise Cummins February 27, 2014
Dr. Cummins is a research psychologist, a Fellow of the Association for Psychological Science, and the author of Good Thinking: Seven Powerful Ideas That Influence the Way We Think.
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