Older Age of Father Linked to Autism, Schizophrenia in Children

a blog by Claire, August 23, 2012

There is a male biological clock. A new study has found that the age of the father when a baby is conceived does matter with regard to passing on gene mutations. The findings, which are published in Nature, may help explain rising rates of autism.

The study was part of a collaboration between deCODE Genetics, a leader in understanding the human genome, and Illumina, a maker of instruments to analyze the genome and their whole genome sequencing project, which is examining associations of diseases with rare variants in the genome. The investigative team sequenced the genomes of 78 Icelandic families with children who had a diagnosis of autism or schizophrenia. They also looked at the genomes of an additional 1,859 Icelanders to provide a larger comparative population.

The average age of the fathers included in the study was 29.7 years old. The scientists looked for mutations in the children's genomes that did not exist in either of their parent's genomes. If a mutation was found, it meant that it arose spontaneously from either the egg or sperm. The study found:

• Fathers passed on four times the amount of mutations as mothers.
• The amount of mutations increased as fathers aged; for example, a 20-year-old father passes on an average of 25 of these errors, while a 36-year-old will pass on 50
• On average, the investigators found a two mutation per-year increase in offspring with each one-year increase in age of the father.

Why do men pass on more genetic mutations? While women are born with their lifetime supply of eggs, men are constantly producing sperm, which is continually being generated by dividing precursor cells, which acquire new mutations with each division. So just because you hear the old saw about Charlie Chaplin fathering children well into old age, you have to remember they are also more likely to pass on mutations. And while most of the mutations are harmless, the investigators identified some that studies have linked to conditions such as autism and schizophrenia.

According to the Centers for Disease Control and Prevention, one in every 88 American children has now been diagnosed with autism spectrum disorder. This is a 78 percent increase since 2007, and increasing paternal age may explain some it, while better screening methods may also explain the rise.

So, just like women need to be aware of their biological clocks and consider options such as egg freezing,men should be aware, too. Sperm freezing when they are younger is always an option.