It’s not just about Mom.
It’s long been known that mothers may affect their child’s health through things like smoking or drinking alcohol, especially during pregnancy. But a growing body of research suggests that a man’s diet, drinking, smoking, and age may contribute to birth defects, autism, obesity, mental illnesses, and other problems in their kids.
Joanna Kitlinska, PhD, an assistant professor of biochemistry and molecular & cellular biology at Georgetown University, looked at dozens of studies on dads' and children’s health. The research suggests “that paternal age, lifestyle, and certain exposures can have an impact on children,” she says.
Here’s how: Age and unhealthy habits cause changes to a man’s genes. Although scientists don’t yet fully understand how it happens, these changes are then passed on to his kids -- perhaps even his grandchildren. For example, a man’s obesity may affect his genes in a way that makes his children more likely to be obese. Or tobaccosmoke may damage a man’s sperm, allowing it to pass on potentially harmful genes to his children.
Most of the studies were able to show only a link between the two and didn’t prove one causes the other. Absolute risks of birth defects and other issues remain low for any one child, and researchers still believe Mom’s health while pregnant has a much stronger effect on their children's health.
“These findings emphasize the fact that the interplay between nature and nurture -- genetics and the environment -- are far more complex than previously appreciated,” says Andrew Adesman, MD, chief of developmental and behavioral pediatrics at Cohen Children's Medical Center of New York. Adesman was not involved in the review.
Here’s a breakdown of what Kitlinska and her colleagues found.
In one study that Kitlinska’s team reviewed, children whose fathers were over 40 had a much higher risk of autism compared to those with fathers under 30. Other large studies backed up this finding. Older fathers also tend to have children who are more likely to get schizophrenia.
Another study links older fathers to higher chances for birth defects such as heart problems and Down syndrome. The risks appeared to go up when dads were 35 and older, with fathers over 50 tied to a more significant risk.
An increased risk doesn’t necessarily mean it’s likely a child of an older father will have birth defects, schizophrenia, or autism, Adesman says.
Obese men are more likely to father children who face a higher risk for obesity. Their children are also more likely to be diagnosed with diabetes, an abnormal metabolism, and certain cancers. This may happen because obesity and poor nutrition cause changes in certain genes directly linked to these conditions.
On the other hand, Kitlinska says, men who had a lack of food as children often have kids -- even grandchildren -- who appear protected against both heart disease and diabetes.
As many as 3 out of 4 children diagnosed with fetal alcohol spectrum disorders have alcoholic fathers. Children with these disorders may have low birth weight, impaired brain development, and learning disabilities.
“With alcohol and many other exposures, it’s been believed that it’s mainly mothers who influence the children directly,” says Kitlinska, whose review challenges that notion.
But, the review says, ongoing alcohol use by a father can affect a child’s genes even if the mother does not drink alcohol before or during pregnancy. Those changes, in turn, could result in a child being born with symptoms of a fetal alcohol spectrum disorder.
Too Much Stress
Fathers with high stress levels may have children who develop behavior problems as a result, animal studies suggest. In those studies, ongoing stress appeared to alter certain genes that were passed on to offspring in mice. Human studies need to be done to confirm and better understand the role of paternal stress.
The review notes there hasn’t been much research in this field, and there may be some limitations. For instance, many studies failed to take into account both paternal and maternal factors in influencing a child’s health.
“The combined effects of both parents may have varying degrees of influence,” researchers write, and the interplay needs to be studied. Also, the researchers say, the studies couldn’t pinpoint whether gene changes were the only cause of a certain characteristic or health problem.
Practice Healthy Habits
Adesman says doctors should consider discussing lifestyle issues with men who want to have kids.
“Although we already have many reasons to curtail or reduce certain risk factors, it is possible that greater appreciation of the risks to their offspring will be compelling for some men,” he says.
Kitlinska says more research needs to be done before any conclusions or recommendations can be made of this “relatively new field of study.” But, her work suggests that fathers-to-be should take good care of themselves: “It’s common sense to have a healthy lifestyle if you are planning to have children,” she says.