Increased rates of autism is associated with the children of teen moms and with children of parents with relatively large gaps between their ages, a comprehensive multinational study of parental age and autism risk has found.
The analysis, which included more than 5.7 million children in five countries, also confirms that older parents are at raised risk of having children with autism.
Co-author Michael Rosanoff said:.
“Though we’ve seen research on autism and parental age before, this study is like no other. By linking national health registries across five countries, we created the world’s largest data set for research into autism’s risk factors. The size allowed us to look at the relationship between parents’ age and autism at a much higher resolution – under a microscope, if you will.”
The study’s goal was to find out if advancing maternal or paternal ages independently increase autism risk, and if so, to what extent.
The key points from the research, according to the press release, are:
Autism rates were 66 percent higher among children born to dads over 50 years of age than among those born to dads in their 20s.
Autism rates were 28 percent higher when dads were in their 40s versus 20s.
Autism rates were 15 percent higher in children born to mothers in their 40s, compared to those born to moms in their 20s.
Autism rates were 18 percent higher among children born to teen moms than among those born to moms in their 20s.
Autism rates rose still higher when both parents were older, in line with what one would expect if each parent’s age contributed to risk.
Autism rates also rose with widening gaps between two parents’ ages. These rates were highest when dads were between 35 and 44 and their partners were 10 or more years younger. Conversely, rates were high when moms were in their 30s and their partners were 10 or more years younger.
The researchers investigated autism rates among 5,766,794 children, which included over 30,000 with autism. These children were born between 1985 and 2004. Researchers followed up on their development until 2009, using national health records for autism diagnoses.
“Advancing paternal and maternal age have both been associated with risk for autism spectrum disorders (ASD). However, the shape of the association remains unclear, and results on the joint associations is lacking. This study tests if advancing paternal and maternal ages are independently associated with ASD risk and estimates the functional form of the associations.
In a population-based cohort study from five countries (Denmark, Israel, Norway, Sweden and Western Australia) comprising 5 766 794 children born 1985–2004 and followed up to the end of 2004–2009, the relative risk (RR) of ASD was estimated by using logistic regression and splines. Our analyses included 30 902 cases of ASD. Advancing paternal and maternal age were each associated with increased RR of ASD after adjusting for confounding and the other parent’s age (mothers 40–49 years vs 20–29 years, RR=1.15 (95% confidence interval (CI): 1.06–1.24), P-value<0.001; fathersgreater than or equal to50 years vs 20–29 years, RR=1.66 (95% CI: 1.49–1.85), P-value<0.001).
Younger maternal age was also associated with increased risk for ASD (mothers
Illustration: Relative risk (RR) for autism spectrum disorder by paternal and maternal age jointly. RR calculated by using the maternal and paternal ages of 25 years as reference. RR estimated by ordinary logistic regression adjusting for sex (male/female), birth year (4-year intervals), and, site (Denmark, Israel, Norway, Sweden and Western Australia). Blue color indicate RR≈1, light green, to yellow and red indicate increasing RR>1. Courtesy S Sandin et al