Risk of Autism Rises with Older Mothers

risk of autismAs parents-to-be rise in age, especially the mother, the risk of autism rises.[1] According to new research, this risk accelerates especially for mothers older than 30.1 The new study, from researcher from the Drexel University School of Public Health in Philadelphia and Karolinska Institute in Sweden, provides deeper insight into how the risk associated with autism rises with parental age, and how it varies between the age of the mother and age of the father.1

In the study, researchers report that fathers’ and mothers’ advancing ages have different impacts on their child’s risk.1 The risk of autism rises more for older mothers, compared with older fathers.1

“The open question at hand really is, what biological mechanisms underlie these age effects?” said Brian K. Lee, PhD, senior author of the study. “The observed differences in risk based on mothers’ and fathers’ ages point to a need to continue investigating underlying mechanisms of autism spectrum disorders that may be influenced by a mother’s age even though most recent discussion has focused on fathers’ and even grandfathers’ ages.”1

The risk of autism has a more complicated relationship to age in women, compared to men.1 Among women giving birth before age 30, the risk of autism showed no association with age, but when the mothers were aged 30 and older, the chance of developing autism rose rapidly.1

According to Lee, the maternal age effect is much stronger than the paternal age effect, although previous studies show otherwise.1 Multiple factors could be to blame, including environmental risk factors and pregnancy complications.1

“The linear, steady increase in risk associated with fathers’ ages is consistent with the hypothesis of increased genomic alterations over the father’s lifespan that can increase risk of autism,” said Lee.1

In this study, Lee and colleagues analyzed a large population registry sample of 417,303 children born in Sweden between 1984 and 2003.1 Researchers used a comprehensive case-finding approach, to identify more autism cases than other might.1 The goal was to study the parental age effects in more detail by looking at possible risks of autism with and without intellectual disability—one of the most serious comorbid diagnoses with autism.1

“When considering risk factors, we can’t necessarily lump all autism cases together, even though they fall under a broad umbrella of autism,” said Lee. “We need to keep an open mind in case intellectual disability might be a marker of a different underlying mechanism.”1

The finding that autism with intellectual disability had a stronger association with older parents, compared to autism without intellectual disability supports the possibility that they may have different mechanisms.1

“The absolute risk of having a child with autism is still approximately one in 100 in the overall sample, and less than two in 100 even for mothers up to age 45,” said Lee.1

[1] Nauert, R. (2014). Risk of Autism Goes Up With Older Parents (Especially Moms). Psych Central. Retrieved on April 30, 2014, from http://psychcentral.com/news/2014/04/23/risk-of-child-autism-goes-up-with-older-parents-especially-mothers/68866.html

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