LOS ANGELES, CA (Catholic Online) - According to the study, compared with younger dads, older fathers pass on significantly more random genetic mutations to their children that increase the risk for these conditions.

Older fathers are also responsible for nearly all of a child's random genetic mutations. A father's age at conception may account for 97 percent of the new mutations found in his offspring. According to the new study led by Augustine Kong at deCODE Genetics in Iceland; this may partly explain the rise in autism diagnoses in recent decades, as high as one in 88 children in the U.S.

Previous studies found that children born to older dads are more likely to have developmental and psychiatric disorders.

This study counters the prevailing notion that older mothers are responsible for genetic problems in children. It must be noted that while older mothers are more likely to have children with chromosomal abnormalities, such as Down syndrome, the recent study finds that it is the father's age that accounts for virtually all of the genetic risk of autism and schizophrenia.

"Our data indicate there is probably much more reason to be concerned with the age of the father," Dr. Kari Stefansson, CEO of deCODE says.

De novo mutations are changes in DNA that arise spontaneously in egg or sperm cells around conception. Most people are born with such mutations, usually harmless. However, some of these mutations have been associated with increased autism risk in previous studies, with that risk rising along with the age of the father.

Sperm, unlike women's eggs are made constantly throughout a man's life. With each cell division, the entire genome is copied - and with three billion base pairs packed into 23 pairs of chromosomes, errors can occur in replication.

Therefore, the older men are, the more times his reproductive cells have continuously divided, generating new genetic material. Environmental factors come into play, such as radiation and other chemical influences that are part of everyday, modern life. In contrast, a woman's egg cells don't divide until they mature in the ovaries.

A 20-year-old father passes on an average of 25 new genetic mutations to his child, while a 40-year-old passes 65. For each additional year in the father's age, children gained two new mutations in their DNA, resulting in a doubling of the de novo mutation rate for every 16.5 years of paternal age; in contrast, a mother transmits about 15 new mutations, regardless of age.

"It's not surprising, and makes sense that it is this way," Dr. Kari Stefansson, CEO of deCODE and senior author of the paper says.

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