Dear Sir,

I hope this briefing note may be of assistance regarding this recent press story concerning the study Advancing Paternal Age and Autism  published Monday in the Archives of General Psychiatry.

The story issued to the press claims fathers over 40 are six times as likely to have an autistic child than fathers aged 15 to 29.

However, I have seen the study and it is out of date before it was written.  It has no relevance to the substantial increase in autism since the mid 1980s.  It is based on data from Israeli military draft board records of 17 year old conscripts born in a six year period commencing no later than 1982.  The failure to mention the distinction between early onset and late onset autism is also highly significant.  

As you know, the new problem since the mid-1980s is late onset autism where the children develop normally and then start regressing around 18 months and older:-

In contrast, the subjects of the study must predominantly be early onset autism cases as they were all born in the early 1980s (and are now at least between 18 to 25 years of age).  As this paper is published in 2006, they can have been born no later than 1988.  It seems the subjects may have been born earlier than 1982 but the authors have oddly failed to state which consecutive six years in 1980 were the birth years of the subjects.  That is critical information because the large increase in "late onset" autism started in the mid-1980's and at that time had not reached the levels we are now seeing.

The study is also based on low accuracy data and the authors state so in their paper.  

The uncertainty over accuracy is called the "confidence interval".  The range of values given in a confidence interval are values which could all be valid.  The problem is that the data is so inaccurate no one can tell for sure which is the right figure - hence the "confidence interval".

What this means is that the risk for fathers 40 and over could be exactly the same as that for those 39 and under.   The lowest risk figure of 2.65 times for fathers 40 and over fathering an autistic child is exactly the same as the highest risk figure for fathers between 30 and 39. 

For sensationalism the story issued to the press cited the higher risk figure which is scaremongering.

The data is so inaccurate the authors give it a wide confidence interval of as low as 2.65 times the risk or as high as 12.46 times the risk for fathers aged 15-29. This is a very large confidence interval - or really it is a "lack of confidence interval" - and this also does not take account of any errors or biases by the researchers which they have missed themselves.

The reason for the inaccuracy is that the number of children and fathers is very small:-

It is not scientific to suggest the conclusions of the paper as reported in the press are valid for the entire world when based on such a small sample - especially one genetically biased to jewish israeli fathers and which has not been subject yet to critical scrutiny by the scientific world post publication.

It is also interesting that the researchers could have chosen data subjects from Israeli draft board records earlier than 1980 but they did not.  The reason for that could well be that there are very few autistics over 25 years old and that is part of the evidence for this new problem since the mid 1980s.

We are told there being no point studying why autism is almost unknown in the Amish, because it is alleged the Amish might be genetically different.  However, we are now told a study genetically limited to jewish people born in Israel in the early 1980s is relevant.  See this extract from the study abstract:-

"Participants  We conducted a study of Jewish persons born in Israel during 6 consecutive years. Virtually all men and about three quarters of women in this cohort underwent draft board assessment at age 17 years. Paternal age at birth was obtained for most of the cohort; maternal age was obtained for a smaller subset. We used the smaller subset (n = 132 271) with data on both paternal and maternal age for the primary analysis and the larger subset (n = 318 506) with data on paternal but not maternal age for sensitivity analyses.

Main Outcome Measures  Information on persons coded as having International Classification of Diseases, 10th Revision ASD was obtained from the registry. The registry identified 110 cases of ASD (incidence, 8.3 cases per 10 000 persons), mainly autism, in the smaller subset with complete parental age data."

Clifford Miller

See: [E mail Sept 6, 2006 Clifford Miller] First time we have hard scientific proof that autism spectrum disorder in British kids has increased 1200 percent since mid 1980s