Older Father, Autistic Child
Harvard Women's Health Watch
Volume 15 - Number 3 - November 2007
The risk of autism rises in children with older fathers, according to a study based on a broad sample of the Israeli population and published last year in the Archives of General Psychiatry.
We've known for a long time that older women (over age 35) are much more likely to give birth to a child with Down syndrome. More recent studies have shown that older men are more likely to father a child who eventually develops schizophrenia. This research adds another serious disorder to the list.
Autism's disabling features, which begin in early childhood, include abnormal social development, unusual behavior, and difficulty communicating. Language is usually impaired, sometimes severely. About two-thirds of autistic adults are mentally retarted, and most cannot live independently.
The Archives study took advantage of Israel's extraordinary complete health records, compiled for almost everyone at draft age (age 17). Researchers had access to intellectual, medical, and psychiatric evaluations of almost all Israeli boys and three-quarters of Israeli girls.
The risk that a man younger than 30 would father a child with autism was about one in a thousand. In his 40s, it rose to about three in a thousand, and after age 50, to five in a thousand. When a man in his 50s has a son, the son's risk of autism approached 1% (one in 100). These correlations persisted even after researchers adjusted for social class and income, the mother's age, and the child's year of birth.
The risk for girls, although relatively small, increased with the father's age even more than the risk for boys did. When fathers were young, about one our of six autism cases was a girl. After age 40, the proportion rose to about one in three. This is one piece of evidence that different genetic factors influence the offspring of younger and older fathers. If fathers' genes are the culprit in autism, how do problems genes arise?
According to one theory, mutations (random changes) are more likely to occur as men grow older. The germ cells that give rise to sperm make copies of themselves throughout life. After several decades, germ cells are copies of copies of copies. There's plenty of room for duplication errors.
Another theory is that genes passed on by older men are not properly marked or "imprinted." Accurate marking establishes which parent a gene comes from and determines whether the gene will be active. If there is an imprinting error, the gene may not function normally.
These days, when men turn 50, friends may reassure them that "50 is the new 30." Medical technology and other improvements in health have made life much more enjoyable for people in middle and late life. But even a healthy and active lifestyle doesn't turn 50-year-old sperm into "the new" 30-year-old sperm. The risk of passing on a genetic vulnerability persists.
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