Autism spectrum disorder, flea and tick medication, and adjustments for exposure misclassification: the CHARGE (CHildhood Autism Risks from Genetics and Environment) case-control study.
BACKGROUND
The environmental contribution to autism spectrum disorders (ASD) is largely unknown, but household pesticides are receiving increased attention. We examined associations between ASD and maternally-reported use of imidacloprid, a common flea and tick treatment for pets.


METHODS
Bayesian logistic models were used to estimate the association between ASD and imidacloprid and to correct for potential differential exposure misclassification due to recall in a case control study of ASD.


RESULTS
Our analytic dataset included complete information for 262 typically developing controls and 407 children with ASD. Compared with exposure among controls, the odds of prenatal imidacloprid exposure among children with ASD were slightly higher, with an odds ratio (OR) of 1.3 (95% Credible Interval [CrI] 0.78, 2.2). A susceptibility window analysis yielded higher ORs for exposures during pregnancy than for early life exposures, whereas limiting to frequent users of imidacloprid, the OR increased to 2.0 (95% CI 1.0, 3.9).


CONCLUSIONS
Within plausible estimates of sensitivity and specificity, the association could result from exposure misclassification alone. The association between imidacloprid exposure and ASD warrants further investigation, and this work highlights the need for validation studies regarding prenatal exposures in ASD.
Department of Epidemiology, CB 7435, University of North Carolina, Chapel Hill, NC 27599-7435, USA. akeil@unc.edu.
Alexander P
AP
Keil
Julie L
JL
Daniels
Irva
I
Hertz-Picciotto
D000818:Animals; D001499:Bayes Theorem; D015982:Bias; D016022:Case-Control Studies; D002659:Child Development Disorders, Pervasive / Q000453:epidemiology* / Q000209:etiology; D002675:Child, Preschool; D004781:Environmental Exposure / Q000009:adverse effects / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007093:Imidazoles / Q000633:toxicity; D016015:Logistic Models; D008297:Male; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000633:toxicity; D016017:Odds Ratio; D010575:Pesticides / Q000633:toxicity; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000453:epidemiology* / Q000209:etiology; D012107:Research Design; D005423:Siphonaptera; D013987:Ticks; D014481:United States
D007093:Imidazoles; D000073943:Neonicotinoids; D009574:Nitro Compounds; D010575:Pesticides; C082359:imidacloprid