Olfactory deficits in individuals with autism spectrum disorder

Introduction: Olfactory abnormalities has been reported in subjects with Autism Spectrum Disorders (ASD)(1,2,3), a neurodevelopmental disorder, characterized by social deficits. However, previous studies considered mainly olfactory threshold or other dimensions of olfactory function (1, 2, 3), usually in isolation or at least in a combination with olfactory threshold. Aim of this study is to examine odor identification and discrimination in ASD compared to typically developing (TD) controls. Materials and methods: Olfactory identification and discrimination were studied, with the “Sniffin’ Sticks” test, in 30 participants, 15 with ASD (2 female and 13 male, mean age 19.13 years) and 15 controls (3 female and 13 male, mean age 21.73). Participants with ASD showed IQ of 103.2±18.5. Controls were volunteer university students matched for chronological age with participants with ASD. Results: Receiver operating characteristic (ROC) analysis indicated a difference between participants with ASD and TD controls in odour identification (area under the curve [AUC]=0.709, 95% confidence interval [CI]: 0.515 to 0.859, P=0.028) and in odour discrimination (AUC=0.782, 95% CI: 0.594 to 0.911, P=0.002). Discussion: According to previous studies (1,2,3), our results confirmed an impairment in odour identification and discrimination in subjects with ASD, which suggest deficits in orbitofrontal cortex, in medial temporal lobe and in cerebello-thalamo-cortical circuits. These findings support the importance of olfactory evaluations as a non-invasive tool to identify cortical dysfunction in ASD. References: 1) Bennetto et al. 2007 2) Dudova et al. 2011 3) Tonacci et al. 2015