It’s the Old Dad Theory, Once Again
October 1, 2008 by Kristina Chew, PhD
Filed under Health
September 5, 2006: Many news sources report on a study in the Archives of General Psychiatry. After analyzing the military records of more than 300,000 men and women in Israel, researchers found that men in their 40’s are nearly six times more likely to have an autistic child.
October 1, 2008: The Telegraph reports on a study by Japanese researchers that found that men over 33 were more likely to have autistic children. The study is published in the British Journal of Psychiatry. 84 children with “high functioning autism” and 208 children without an ASD were in the study which, it’s acknowledged, was small in scope:
Children whose fathers were over 33 were 1.8 times more likely to have autism than those fathers were under 29. Men who fathered children between the age of 29 and 32 were 30 per cent more likely to have an autistic child.
“High-functioning autism” was defined, for the purposes of this study, as having a full-scale IQ of at least 70, with a DSM–IV autistic disorder or related diagnosis.
No association between autism and maternal age was found in the new study. Older mothers have also been suggested to be more “at risk” for having an autistic child, according to a study conducted by researchers at Kaiser Permanente’s Division of Research in Oakland, California, under lead author, epidemiologist Lisa Croen.
But do these “old dad” theories too quickly put the blame—unrightly—-on fathers?
Maybe it’s me, but I’m not sure why these reports create so much discomfort? I don’t see “blame” being laid–what I see is looking at potential genetic influences and probabilities through aging. It was my being over 40 that made amniocentesis a recommended procedure during pregnancy because of increased probability of Down Syndrome and other chromosomal anomalies.
Even though we weren’t working with cutting edge information, we assumed that we might have higher probabilities of atypical outcomes or complications compared to a younger couple. If either I or my husband, or both, have accumulated point mutations as a function of aging which contributed to Eleanor’s subsequent diagnosis, well so be it. I don’t take it personally and don’t feel that blame enters into it.
I’m uncomfortable when people start talking about “blame” with this type of research, although I know that they will. I’ve been lucky enough to talk to mothers of adults who lived through the “refrigerator mother” years, and I’d like to think that stigmatization like that wouldn’t happen again. I’d like to think it, but I’m also a pessimist.
Hopefully when we do find out what “causes” autism (if we ever do find one thing, which I doubt- it seems likely to me that it’s a combination of things), people are not going to point fingers at each other.
The same group that looked at Israeli military conscripts published another article in the peer reviewed journal ‘Schizophrenia Bulletin’ along the same lines, but reported slightly different results in the respective abstracts:
http://www.ncbi.nlm.nih.gov/pubmed/18796466?
The study found fathers under 20 and over 45 were more likely (slightly) to have a child with relatively poorer social functioning but so to were mothers of who were over 45 years of age when they had a male child.
Behavioral Genetics is a soft science based on ‘psychological’ theory and there appears to an increasing volume of papers which can be described as naval gazing… Are parents of ASD children less sociable than control parents, do parents of ASD children have less eye contact than controls, are parents of ASD’s older than control parents?
What the Behavioral Geneticists miss is that the parents of ASD children do not meet any diagnostic criteria for ‘Autism’.
Behavioral Genetics (the polygenic hypothesis) continues to be a theory in search of data…. No gene that ’causes’ autism has ever been identified, not one.
That doesn’t mean that mild genetic influences aren’t a part of the overall picture but just as the early pioneers in autism research were heavily influenced by Freudian theory and psychodynamics, current pschiatric opinion is heavily influenced by Behavioral Genetics when it comes to interpreting data.
Genetic influences operate in nearly all complex multifactorial conditions, even in HIV susceptability and leprosy.
I wish I could find the article I read a couple years back, that claimed to show a link between parents with a diagnosed learning disability and an increase in autism rates among their children. That caught my eye, as my husband has dyslexia and I had extreme difficulty with mathematics.
I think the old dad theory is credible in light of the mounting research pointing towards spontaneous genetic mutation. Of course, I’m just a layperson.
The problem with the “old dad” observation being due to genetic changes is that genetic changes would be completely 100% heritable and can only accumulate. The only way for them to not accumulate would be for individuals having too many of them to be unable to reproduce.
In other words, if one ancestor had those genetic changes, all descendents of that ancestor would have them too. Not every gene gets transmitted, but if there is no bias in which ones do get transmitted (except by the phenotype they produce), they would accumulate until non-reproducing phenotypes were produced. If the incidence of aged fathers increased by a few percent, that irreversibly skews the entire human gene pool to the aged father genotype.
I think a more likely explanation for the “old dad” observation is epigenetic changes. Epigenetic changes could easily be programmed in as a father ages, cause a different phenotype, and then are “reset” in the next generation. Epigenetics could explain the “young dad” observation too (which a genetic mutation hypothesis has a hard time with).
Epigenetic changes are sufficient to cause autism. It is the lack of being able to interpret DNA methylation due to the loss of the MeCP2 gene that causes Rett Syndrome.
An old dad and a young dad could also affect the epigenetics of the child based on stress levels in the mother. Having the father of your child be a male who could not protect you or the child is going to invoke stress and (I would guess) invoke the high stress phenotype in utero.
I follow on the speculation about the epigenetics, but this does skirt on blame in my mind,
“…Having the father of your child be a male who could not protect you or the child is going to invoke stress and (I would guess) invoke the high stress phenotype in utero.
Is there any data showing that the children of substance-abusing dads, absent dads or abusive dads have higher prevalence of autism?
That might be hyperbolic, but I am really not following the point you are making.
I don;t buy it. Larry King had two boys in his 70s, neither on the spectrum. Tony Randall had a kid in his 70s also.
Bonnie – there’s a proven correlation between Downs and age of mother. I could list several celebrity mothers who didn’t give birth to Downs babies, but that doesn’t disprove the correlation.
I can’t understand why there isn’t more talk about whether the fathers might have traits that make them have children later – like traits in the broader phenotype of autism. Both having children later and having children with autism could be related to the same genes.
I think this is just another study that shows they can make a study “prove” whatever they want.
BTW, my husband was 38 and 39 when our boys were born.