On any given day you can open the celebrity section of the newspaper or navigate to the hottest celebrity blog and read about aging mothers and fathers. Hollywood stars are known for waiting later in life to start families, but researchers say men who wait longer may be increasing the risk of passing genetic mutations like autism on to offspring.
Where It All Began
J.B.S. Haldane was the first to notice how genetics played a part in the disease process. It was the 1930s and he recognized that families appeared to pass hemophilia, a blood disorder, from one generation to another. The X chromosome is responsible for the blood disorder, which lead Haldane to the conclusion that genetic conditions or mutations came from dad, not mom. At the time science was unable to prove the theory, but eventually science caught up with Haldane’s mind and he was proven correct. The holder of the X chromosome is responsible for more genetic mutations than the holder of the Y chromosome (mom). Furthermore, current research suggests the age at the time of paternity may play an important factor in those genetic mutations.
How Mutations Increase With Age
All sperm are generated from precursor cells. Men continue to produce sperm for a lifetime, but with each division of the cells new mutations occur. It is the latter mutations that occur with age that sparked the interest of researchers. In a study of nearly 80 trios (mother, father and child) researchers found that fathers passed on about 4X the rate of mutations as mom and the greatest number of mutations was consistently recorded in older paternal mates. For instance, a 36 year old man will pass on as many as two times the mutations as a man just 20 years old. In a 70 year old man that number increases to eight times the 20 year old rate.
Researchers noted that many genetic mutations have no known impact on overall health or lifespan, while others can have extreme impact on quality of life. Some studies have linked genetic mutations to autism and certain mental disorders like schizophrenia. The study did not definitely connect paternal age to disease-causing genetic mutations, but the implication is there.
There are other studies on autism that link paternal age to autism risk. Some studies have even gone so far as to list the genetic mutations that could cause autism, most of which come from the paternal side of creation.
There is no known cause of autism and no definitive link between paternal age and genetic diseases, but as the average paternal age increases so does the rate of autism, according to some researchers and authors. On the other hand, genetic mutations are thought to be a part of the life process known as natural selection.
Source: Callaway, Emma. "Fathers Bequeath More Mutations As They Age." Nature.com. Nature Publishing Group, 22 Aug. 2012. Web. 04 Sept. 2012.