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Sniff response may be a marker of autism spectrum disorder

Non-verbal tests that measure sniff response may be useful in identifying autism spectrum disorder, as recent study findings show children with autism do not adjust their sniff response when smelling pleasant or unpleasant scents.

“Autism spectrum disorder is associated with impaired sensory-moto coordination. One type of brain mechanism subserving sensory-motor coordination is referred to as internal action models, [which] allow action initiation based on sensory expectations alone and ongoing refinement of motor output based on sensory input flow,” study researcher Liron Rozenkrantz, a PhD student at the Weizmann Institute of Science in Rehovot, Israel, and colleagues wrote in Current Biology. “Because sniff response entails fine adjustment of motor process (the sniff) in precise accordance with sensory input (the odor), it can be considered an [internal action model].”

To measure sniff response, researchers created a computer-controlled air-dilution olfactometer equipped for children that simultaneously delivered odors and measured nasal airflow. Researchers used the machine to measure sniff response to pleasant (rose or shampoo) and unpleasant (sour milk or rotten fish) odors among 18 children with autism and 18 age- and gender-matched controls with typical development. The mean age of the participants was approximately 7 years. The 10-minute procedure included of 20 trials that were 1 to 2 seconds long with a 30-second intermission between each trial.

Noam Sobel

While typically developing children had adult-like sniff responses, children with autism had a significantly different sniff response and sniffed equally regardless of if the odor was pleasant or unpleasant.

An equal sniff response to both odors correctly identified children with autism 81% of the time (P < .001).

Further, increasingly irregular sniff response was associated with increasingly severe autism (P < .001), particularly with social (P < .001) skills, but not motor skills (P > .18).

“We can identify autism and its severity with meaningful accuracy within less than 10 minutes using a test that is completely non-verbal and entails no task to follow,” study researcher Noam Sobel, PhD, of the Weizmann Institute of Science, said in a press release. “This raises the hope that these findings could form the base for development of a diagnostic tool that can be applied very early on, such as in toddlers only a few months old. Such early diagnosis would allow for more effective intervention.” – by Amanda Oldt

Disclosure: Please see the full study for a list of all authors’ relevant financial disclosures.