Recent prevalence rates of autism in the U.S. have been reported to be on the rise, from 1 in 68 in earlier years, to a high 1 in 45 in 2014 according to the U.S. Centers for Disease Control and Prevention. The reason for the reported rise, however, is even more surprising.
Nature World Report stated that the rates have been steadily rising in the country over the past decades. In the year 1975, only one in 5,000 are reportedly diagnosed with the debilitating condition. Spanning between the 1970s to the 1980s, about one person would be diagnosed positive in 2,000.
“There’s a lot of controversy about that,” Dr Jeff Milunsky, MD, director of clinical genetics and associate director of the Center for Human Genetics at Boston University, told WebMD.
It was found that the new reported rates have been reached due to a “tweak” in the survey questionnaire used. This tweak caused the prevalence rate to rise from 1.25% to 2.24% in 2014, according to Forbes.
For the earlier 2011-2013 survey, parents answered three questions from the National Health Interview Survey conducted by the CDC. The first question asked if the child had an intellectual disability. The second asked for any developmental delay. The third asked the parents if the child had been diagnosed with any of the several conditions listed, which included Down syndrome, sickle cell anemia, and Autism Spectrum Disorder.
The 2014 survey, on the other hand, had parents answering three questions, but the survey questionnaire was tweaked. The first question also asked for any intellectual disability, but the second question directly asked the parents if their child had an ASD diagnosis. The third question asked about any developmental delays.
This change of questions to emphasize autism raised prevalence rates by almost twice the previous rate, from 2011-2013 to 2014. Prevalence rates for 'other developmental disorders,' however, dropped from 4.84% in 2011-2013 to 3.57% in 2014.
Study author Benjamin Zablotsky, from CDC's National Center for Health Statistics, stated in the report that the way researchers asked parents regarding ASD did ultimately affect the estimated prevalence rate, as suggested by the results.
“This explanation suggests that ASD prevalence estimates based on the 2014 data are more sensitive in capturing the full population of children with ASD than estimates based on the 2011–2013 data,” wrote the researchers. “When the ASD question is asked directly and when it comes before the other DD question, it is likely to receive more attention and more thoughtful responses.”
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