The prevalence of autism is increasing so dramatically in the U.S. that the Centers for Disease Control and Prevention calls it a public health concern. Since the 1960s, autism rates have increased ten-fold, according to a 2011 article in the Archives of General Psychiatry.
“Autism is the fastest-growing serious developmental disability in the U.S.,” according to Autism Speaks, a research and advocacy organization.
In March 2014 by the Centers for Disease Control released new prevalence rates for Autism Spectrum Disorder (ASD): 1 in 68 children.
“CDC considers ASDs an urgent public health concern and recognizes that more children are being identified with an ASD than in the past,” according to ADDM community report.
Researchers say that better awareness of autism and improved diagnosis procedures alone cannot account for all of the growing number of cases.
To put the latest autism rate in perspective, more children are diagnosed with autism each year “than diabetes, AIDS, cancer, cerebral palsy, cystic fibrosis, muscular dystrophy or Down syndrome – combined,” according to the advocacy group Autism Speaks, which based that conclusion on data from the Child & Adolescent Health Measurement Initiative.
Backed by other research
A study conducted in British Columbia covering about the same birth years showed a similar increase in autism rates. Published in 2008 in the Journal of Autism and Developmental Disorders, the study concluded that diagnostic substitution alone could account for the increase.
Another article, published in Epidemiology in 2009, reached a similar conclusion. “Younger ages at diagnosis, … changes in diagnostic criteria, and inclusion of milder cases do not fully explain the observed increases.”
Yet, rates of autism indeed continue to increase.
Researchers are studying many possible reasons to explain the increase and the cause likely won’t point to a single trigger. In addition to terbutaline exposure, immune function, maternal stress, and illness have been mentioned as risk factors. Autism Speaks cites the possibility of a genetic predisposition to autism, with non-genetic risk factors increasing the possibility of ASD when exposed to an environmental trigger.
Extended exposure to terbutaline is an environmental risk factor that is documented in medical records – and could have been avoided. As early as 1984, an article in the Journal of Reproductive Medicine questioned the effectiveness of terbutaline for treating preterm labor.
Andrew Zimmerman, director of medical research at the Center for Autism and Related Disorders at Kennedy Krieger Institute in Baltimore, estimates that prenatal exposure to drugs, such as terbutaline, could account for about 5 percent of all autism cases.
Zimmerman was the senior researcher on a 2011 study that showed a four-fold risk for ASDs in children born to mothers exposed to terbutaline for longer than 48 hours during the third trimester. That same study, published in the Journal of Neurodevelopmental Disorders, showed that exposure to drugs other than terbutaline for preterm labor had no increased risk for autism.
Never tested for preterm labor
The FDA approved terbutaline in 1978 to treat asthma. During the 1990s, terbutaline became the most widely used drug in this country to treat pre-term labor. However, drug manufacturers never tested terbutaline for the treatment of preterm labor.
Children in the CDC surveillance network are screened for autism at age 8. That puts the birth years for this increase from 1994 to 2000.
In 2011, the FDA required drug manufacturers to place a prominent warning label on terbutaline packages. That warning limits the use of terbutaline injections to between 48 and 72 hours and warns against any use of oral terbutaline tablets for pre-term labor.
- Autism and Developmental Disabilities Monitoring Network Surveillance and Centers for Disease Control and Prevention. Prevalence of autism spectrum disorders–Autism and Developmental Disabilities Monitoring Network, 14 sites, United States, 2008. MMWR Surveill Summ. 2012Mar.30;61(3):1–19.
- Autism Speaks [Internet]. [cited 2012Aug.1]. Available from: http://www.autismspeaks.org.
- CDC. ADDM Community Report 2009. 2010Mar.11;:1–36.
- Cotton DB, Strassner HT, Hill LM, Schifrin BS, Paul RH. Comparison of magnesium sulfate, terbutaline and a placebo for inhibition of preterm labor. A randomized study. J Reprod Med. 1984Feb.;29(2):92–7.
- Croen LA, Connors SL, Matevia M, Qian Y, Newschaffer C, Zimmerman AW. Prenatal exposure to β2-adrenergic receptor agonists and risk of autism spectrum disorders. J Neurodev Disord. 2011Aug.27;3(4):307–15.
- Hallmayer J, Cleveland S, Torres A, Phillips J, Cohen B, Torigoe T, et al. Genetic heritability and shared environmental factors among twin pairs with autism. Archives of General Psychiatry. 2011Nov.;68(11):1095–102.
- SFARI [Internet]. Pregnancy drugs increase baby’s autism risk, group claims. [cited 2012Aug.21]. Available from: http://sfari.org