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A new study found no association between how much Utah families earn and their children's risk of being diagnosed with intellectual disabilities and autism spectrum disorders.
That finding, published Thursday in the journal Autism Research, contradicts earlier studies that suggested links between autism and higher income, and between intellectual disabilities and lower income.
Judith Pinborough-Zimmerman, assistant research professor at the University of Utah Department of Psychiatry, and colleagues used census data to analyze 26,108 8-year-olds born in Salt Lake, Davis and Utah counties in 1994.
They examined the gender and ethnicity of the children, the age and education levels of the parents, and how household income changed over eight years, comparing families who had a child with autism or an intellectual disability to the general population.
They found "no clear association" between income and the risk for autism or intellectual disabilities. The Centers for Disease Control and Prevention believes that by age 8, most children with autism have been diagnosed.
One issue researchers may need to examine: "Are Utah's higher rates [of autism] in part because we are providing good services for various income groups?" Pinborough-Zimmerman said.
Autism spectrum disorders (ASD) vary widely in severity but are characterized by unusual behaviors and difficulty with social interaction and communication. Amid a significant increase in the reported incidence of ASDs, the Centers for Disease Control and Prevention has stressed the need for identifying risk factors.
A 2007 study revealed that one in 133 Utah children had an ASD — the third highest rate in the 14-state study. Utah researchers continue to examine and track children with autism born in 2000, 2002 and 2004 in an effort to evaluate prevalence and risk factors.
Further analysis of income and birth order is underway; a first-of-its-kind geographical study of Utah's autistic children is expected to come out early next year.
For the new study, Pinborough-Zimmerman and colleagues identified children with ASD and/or intellectual disabilities in the three-county area using the Utah Registry of Autism and Developmental Disabilities, a population-based surveillance program.
They looked at a range of demographic factors and found:
• Children with ASD but not intellectual disabilities were significantly more likely to be male and to have mothers of white, non-Hispanic ethnicity.
• Children with both ASD and intellectual disabilities also were more likely to be male, but were more likely to have mothers older than 34 years of age.
• Children who had intellectual disabilities but not ASD were significantly more likely to have fathers older than 34 years of age and significantly less likely to have mothers with more than 13 years of education.
Pinborough-Zimmerman is interested in understanding why data suggests white, non-Hispanic mothers seem to have a higher risk for having autistic children. That could suggest there's not actually a higher risk for that ethnic group, but that Hispanic families are having more difficulty accessing diagnosis and services, she said.
Researchers are hoping to secure a grant to increase the screening and diagnostic service access for Hispanics in Utah.
The Utah Department of Health collaborated on the new study. Harper Randall, medical director for the department's Division of Family Health and Preparedness, said in a statement: "This study, despite the small sample size, is an example of the importance of exploring the many variables, that in combination, may result in an increase risk of developing ASD."
Pinborough-Zimmerman said one strength of the study was its use of multiple educational and health source records to include a wide spectrum of ASD cases.