Older dads raise risk of genetic disorders
A flurry of new genetic and epidemiological studies is chipping away at a much-cherished male fantasy: Sperm, it turns out, don't age as well as some men imagine.
At least 20 exceedingly rare but potentially devastating genetic disorders, including dwarfism and other skeletal deformities, have now been linked to older fathers. Men who have families later in life also have a higher risk of fathering children with schizophrenia, studies show.
Researchers last week reported that men over 40 are nearly six times as likely to have an autistic child as those under 30.
Despite the gloomy statistics, scientists stress that the vast majority of children born to men of all ages are healthy, and that the deterioration of sperm over time isn't nearly as precipitous as that of human eggs. Down syndrome, for example, occurs in fewer than 1 in 1,000 women under 30. At 35, the risk jumps to 1 in 400. By 50, it's 1 in 6.
"There's no question that females have a much higher risk of chromosomal aberrations as they age," says Terry Hassold of the University of Washington, an authority on chromosome defects in human sex cells.
But it's also clear that more men are putting off first-time parenthood — or, in some cases, fathering new broods with younger spouses. Since 1980, U.S. birth rates have shot up as much as 40 percent for men aged 35 to 49. Meanwhile, they've decreased up to 20 percent for men under 30, according to the National Center for Health Statistics.
When researchers at the Lawrence Livermore National Laboratory examined sperm collected from healthy men ages 22 to 80, they found a steady increase in the number of broken DNA strands and other genetic rubble within cells as they age.
The report, published this summer in the Proceedings of the National Academy of Sciences, showed men in their 40s generally had twice as much DNA damage as men in their 20s.
Due to concerns over genetic damage and its potential health consequences, the American Society for Reproductive Medicine, which sets standards for sperm banks around the country, has set the cutoff age for semen donors at 40.