In an analysis of U.S. medical records, counties with higher rates of genital deformities in newborn males also had higher rates of autism and intellectual disability (ID). This suggests the possibility of congenital exposure to harmful environmental factors such as pesticides.
Male fetuses are particularly sensitive to toxins such as environmental lead, sex hormone analogs, medications, and other synthetics. Parental exposure to toxins is linked to a large portion of congenital reproductive malformations, such as micropenis, hypospadias (urethra on underside of the penis), undescended testicles, and others.
In individual counties, autism rates jumped 283 percent for every one percent increase in frequency of genital malformations. Intellectual disability rates increased 94 percent.
Non-reproductive congenital malformations and viral infections in males were also associated with double digit increases in autism and ID rates.
“Autism appears to be strongly correlated with rate of congenital malformations of the genitals in males across the country,” said study author Andrey Rzhetsky, Ph.D., professor of genetic medicine and human genetics at the University of Chicago.
“This gives an indicator of environmental load and the effect is surprisingly strong.”
Although autism and intellectual disability are partly genetic, environmental causes are thought to play a role as well.
To identify potential environmental links, the researchers analyzed insurance claims data that covered nearly one-third of the U.S. population. Congenital malformations of the male reproductive system were used as an indicator of parental exposure to toxins.
Almost all areas with higher rates of autism also had higher rates of ID, which suggests the presence of environmental factors. Futhermore, male children with autism were almost six times more likely to have congenital genital malformations. Female incidence was linked with increased malformation rates, but only slightly.
“We interpret the results of this study as a strong environmental signal,” Rzhetsky said. “For future genetic studies we may have to take into account where data was collected, because it’s possible that you can get two identical kids in two different counties and one would have autism and the other would not.”
Source: University of Chicago