A new study that looked at a large birth cohort (almost 5 million participants) over a 10 year period has announced that maternal age is an indicator of developing autism with an approximately 50% higher risk for a woman in her forties than a woman in her twenties.
The researchers looked at the records for all births in California between Jan 1990 and Dec 1999. Cases of autism were identified from this cohort using the records from the Early Start Report (ESR) for children under three, and the Client Development and Evaluation Report (CDER) for children over three.
A diagnosis of autism was defined as either positive for Developmental Disabilities on the ESR, or an autism level of one a CDER record/ICD code for autistic disorder. After excluding children from multiple births and those with missing data there were 12,159 cases and 4,935,776 controls.
Thats an interesting autism rate of 0.2% which might indicate more than maternal age that ESR or CDER is not that good at catching autism diagnoses as its a very low rate compared to the US national 1%.
This paper also lacks strength when looking at confounding factors – admittedly a tricky proposition as we don’t know what causes autism – but it may be of interest that the confounding factors that they did account for were mainly ethnocentric i.e. race, gender etc and that they found that yep – whites were mainly very well represented. It seems very likely therefore that of possibly more interest that maternal age might be that not enough efforts are being made by local authorities to go into non-white enclaves.