Until he met his wife, Trumbo, a sports instructor, had spent time with kids and liked them but rarely thought of having any. Now he looks forward to teaching his son what he's taught so many others.
(3 of 6)
Investigators in the Nature paper studied the genomes of 78 mother-father-child trios in Iceland in which the child had schizophrenia or autism but the parents had neither. Comparing these genomes with those of Icelanders as a whole, they were able to pinpoint mutations that turned up only in autistic or schizophrenic kids and in the sperm of their fathers. And that led them to conclude that a whopping 97% of the relevant genetic errors were attributable to the dad alone. Dr. Dolores Malaspina, a professor of psychiatry and environmental medicine at New York University Langone Medical Center, conducted similar work focusing on schizophrenia in Jerusalem and reached similar conclusions: 27% of all cases of the disease there could be attributed to the father's age.
Harder to reckon than schizophrenia and autism are low birth weight and premature birth. Most people assume these are the result of nutritional deficiencies or problems with the mechanics or hormonal environment of the womb. But things are more complex than that.
In the May paper, investigators studied more than 755,000 births in Missouri from 1989 to 2005, correlating the ages of the parents to the birth weights and gestation periods of the babies. The numbers were revealing: babies fathered by men in the 40-to-45 age group were at 24% greater risk of stillbirth than those fathered by men in the 25-to-29 category. The babies in the older-father group were also at 19% greater risk of low birth weight, 13% higher risk of preterm birth and 29% increased risk of very preterm birth. The reason is that while it's true that anomalies in the womb account for a share of gestational problems, babies are not passive players in the game. If something in the genes inherited from the dad causes problems in the chemical cross talk between mother and child during the nine months they're joined, other things can get thrown off too. "We don't know the exact mechanism," says Dr. Hamisu Salihu, a professor of epidemiology and obstetrics at the University of South Florida and a co-author of the paper. "The process of delivery is poorly understood, but we know there are certain genes that promote it."
Tellingly, some of the same gestational problems that occur with older dads also show up in the 20-to-24 demographic, with a 31% greater risk of very preterm birth and a 57% greater risk of low birth weight. That would seem to contradict the age link, but Salihu says otherwise. Smoking, poor sleep habits and junk-heavy diets are more common in young men and can all lead to epigenetic changes--damage to the chemical markers that sit atop the genome and regulate how it works.
For investigators, epigenetics throws an entirely different X factor into the equation. It's not just habits like smoking and eating poorly that can contaminate the body and erode the epigenome; there's a whole soup of environmental variables, including endocrine disrupters, pesticides, lead and synthetic estrogens. The epigenomes of all people can be damaged by this chemical assault, but the more years you've been around, the more the toll mounts.
Global Oldies