The Toronto Concussion Study: Sense of smell is not associated with concussion severity or recovery

ABSTRACT

Objective

To examine sense of smell as a biomarker for both severity and duration of post-concussion symptoms.

Methods

Participants were recruited prospectively from an outpatient concussion clinic. Sense of smell was assessed using the University of Pennsylvania Smell Identification Test (UPSIT) within 7 days, and 4, 8 – or 16-weeks post-injury. UPSIT normative data were used as normal controls. The main outcomes were: symptom severity on the Sport Concussion Assessment Tool 3 (SCAT3) symptom inventory and time to physician-declared recovery.

Results

A total of 167 participants (mean age 32.9 [SD, 12.2] years, 59% female [n = 99]) were classified at 1 week post injury as follows: severe hyposmia in 5 (3%), moderate hyposmia in 10 (6%), mild hyposmia in 48 (29%), and normosmia in 104 (62%) individuals. A convenience sample of 81 individuals with concussion were tested at follow-up. Acute impairment of sense of smell following concussion was not associated with symptom severity on the SCAT3 or time to recovery. Sense of smell was stable from baseline to follow-up in this population.

Conclusion

This study provides evidence that routine testing of sense of smell in individuals with concussion is not warranted as a biomarker for severity of concussion and concussion recovery.

KEYWORDS:

• Concussion
• traumatic brain injury
• smell
• olfactory dysfunction
• symptom reporting

Acknowledgments

We would like to acknowledge the Toronto Rehabilitation Institute Foundation for their continuous support of this study and the Hull-Ellis Concussion and Research Clinic. Additionally, we would like to acknowledge the clinic physicians: Drs. Alan Tam, Alice Kam, and David Lawrence who were instrumental in assessing recovery in this study, as well as the Hull-Ellis Concussion and Research Clinic staff.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Toronto Rehabilitation Institute Foundation.