Olfaction Impairment Patterns: COVID-19 vs Mild Cognitive Impairment

One African man Trying to Sense Smell of a Lemon at home during the day, smell blindness is one of the possible symptoms of covid-19.
How can persistent hyposnia from COVID-19 be distinguished from olfactory impairment exhibited by those with mild cognitive impairment?

A reduced ability to smell licorice, cinnamon, and lemon is associated with COVID-19 hyposmia and may help differentiate it from mild cognitive impairment (MCI), according to study results presented at the American Academy of Otolaryngology-Head and Neck Surgery Foundation (AAO-HNSF) 2022 Annual Meeting and OTO Experience, held in Philadelphia, Pennsylvania, September 10 to 14, 2022.

Olfactory dysfunction, a common symptom of COVID-19 infection that persists in nearly 1 in 8 patients, is also associated with MCI. Because this dual association may make it more difficult to detect MCI in patients who have had COVID-19, researchers sought to distinguish patterns of olfactory impairment related to MCI vs COVID-19 hyposmia.

The prospective study included patients with confirmed COVID-19-associated hyposmia (n=73), MCI (n = 58), and a control group of patients with normal olfactory function (n=86).

Olfactory testing was done with the Affordable Rapid Olfaction Measurement Array at initial enrollment, and MCI was determined with use of the Montreal Cognitive Assessment. Multivariate logistic regression was used to assess associations between variables and the etiology of olfactory dysfunction.

Compared with the control patients, the inability to smell licorice, cinnamon, and lemon at the lowest 3 concentrations increased the odds of COVID-19 hyposmia by 10.8 (95% CI, 4.6-25.6), 5.7 (95% CI, 2.7-11.7), and 5.3 (95% CI, 2.6-10.8), respectively, after controlling for age and sex. The inability to smell coffee (odds ratio [OR] 9.9; 95% CI, 2.02-48.1), eucalyptus (OR 6.7; 95% CI, 2.2-20.0), and rose (OR 4.0; 95% CI, 1.7-9.7) was associated with MCI, although the reduced ability to smell licorice, cinnamon, and lemon was not.

The reduced detection of licorice, cinnamon, and lemon was associated with a 16.5 OR (95% CI, 6.6-41.3) for COVID-19 hyposmia when combined into a composite score and compared with the control patients. This composite score was not significantly associated with MCI (OR 1.2; 95% CI, 0.6-2.2) and was effective in discriminating patients with COVID-19 from those with MCI (receiver operating characteristic area under the curve=0.76).

“Distinct patterns of impaired olfaction were noted for COVID-19,” stated the researchers. “We show that this etiology-specific phenotype has good discriminative performance when differentiating from MCI-associated hyposmia, which may allow for continued utilization of olfactory screening for MCI even among those with previous COVID-19 infection.”


Farrokhian N, Villwock J, Lucas J, Macke J, Rea E, Yu K. Etiology-specific olfactory phenotypes for COVID-19 and mild cognitive impairment. Abstract presented at: AAO-HNSF 2022 Annual Meeting and OTO Experience; September 10-14, 2022; Philadelphia, PA.

This article originally appeared on Pulmonology Advisor