Association Between Parental Age and Autism Spectrum Disorders (ASD)
A large-scale study involving single live-born children from Denmark, Norway, Sweden, Western Australia and Israel has established an association between the age of the parents and the risk of having a child with ASD, but this association is unclear and other contributing factors are lacking.
Data from roughly 5.76 million children was analyzed to understand the correlation between the age of the parents and the risk of ASD in their children. From the maternal data there appeared a U-shaped association with the age of 30 being the lowest occurrence of ASD and the ages below 20 and above 40 showing a significant increase in the numbers of ASD. For the paternal data, risk remained a direct correlation between the age of the father and the increased occurrence of ASD.
Other factors that showed an increase in risk were the combined age effect. When the age disparity exceeded 10 years, the risk of ASD increased as well. GraphThis was most dramatic when the mother was significantly older than the father.
What was not studied was the correlation between these age disparities and their socio-economic, genetic, and/or psychological characteristics that contributed to an increased risk of ASD.
In Denmark little or no correlation was found between ASD and social status, but access to health-care was equally available for all and free of charge. Young mothers and those with limited resources may be most at risk due to limited prenatal care, perinatal care and resources. It is known that perinatal and prenatal complications are associated with ASD risk, as well as, a deficiency in folic acid. Although other groups showed an increase in ASD among teen mothers, in Israel this was not the case, and not enough information has been acquired to understand why this occurred. Other studies that adjusted for lack of prenatal care have seen a monotone association with maternal age.
For genetic compatibility, large trait and age differences between parents have been shown to be associated with adverse pregnancies. A study in the UK on height, and a study by MartinFieder andSusanneHuberon regarding certain combinations of parental age have shown fitness benefits for parents that select partners closer to their age and stature. During this study, these factors were not taken into account, and thus could alter the observed results.
This study also lacks parental psychiatric history, as drugs like valproic acid and thalidomide when administered during pregnancy have shown abnormalities of the serotonergic system that is often observed in ASD.
Other factors not taken into account are obstetric complications, gestational age and birth weight, all of which can contribute to increased risk in ASD. Although this study group was very large, a majority of the data came from parents within the lowest risk age group, mothers 25-35 and fathers 29-39. More date needs to be collected within the age range with the greatest risk in order to better understand the contributing factors that increase the risk of ASD.
Fortunately, this study gives researchers a starting point to look further into the more complex factors that are attributing to the increased risk of ASD, and although this does not give parents all the answers, it does give a direction to continue looking for possible causes and hopefully developing tests for parents to screen for ASD risks.