Prevalence and correlates of parosmia and phantosmia among smell disorders

Abstract

Among those many individuals who experience a reduced odor sensitivity (hyposmia/anosmia), some individuals also have disorders that lead to odor distortion, such as parosmia (i.e. distorted odor with a known source), or odor phantoms (i.e. odor sensation without an odor source). We surveyed a large population with at least one olfactory disorder (N = 2031) and found that odor distortions were common (46%), with respondents reporting either parosmia (19%), phantosmia (11%), or both (16%). In comparison to respondents with hyposmia or anosmia, respondents with parosmia were more likely to be female, young, and suffering from post-viral olfactory loss (P < 0.001), while respondents with phantosmia were more likely to be middle-aged (P < 0.01) and experiencing symptoms caused by head trauma (P < 0.01). In addition, parosmia, compared to phantosmia or anosmia/hyposmia, was most prevalent 3 months to a year after olfactory symptom onset (P < 0.001), which coincides with the timeline of physiological recovery. Finally, we observed that the frequency and duration of distortions negatively affects the quality of life, with parosmia showing a higher range of severity than phantosmia (P < 0.001). Previous research often grouped these distortions together, but our results show that they have distinct patterns of demographics, medical history, and loss in quality of life.

Keywords: anosmia; distortion; impairment; olfactory; smell.

Fig 1.

Parosmia and phantosmia are distinct disorders in demographics and etiology. The demographics of respondents were distinct by age (A), sex (B), and etiology (C). Colors and icons represent olfactory disorders: green with a distorted grid icon represents individuals with parosmia, orange with an outlined cigarette icon represents individuals with phantosmia, as cigarette smell was a common phantom smell reported in our sample pool (14% of terms), and purple with a nose deny icon represents individuals with neither parosmia nor phantosmia, but who reported an issue with smell (hyposmia/anosmia). Normalized prevalence represents the frequency difference between anosmia/hyposmia (baseline) and the other two olfactory disorders (parosmia or phantosmia). Error bars represent bootstrapped standard errors.

Fig. 2.

Parosmia and phantosmia are distinct disorders by medical history. (A) The two disorders were distinct in the time course of disease (A–C), and amount of nasal congestion (D). Normalized prevalence represents the frequency difference between anosmia/hyposmia (baseline) and the other two olfactory disorders (parosmia or phantosmia). Error bars represent bootstrapped standard errors.

Fig. 3.

Text analysis of descriptions of parosmic episodes by individuals with parosmia. (A) Word cloud of nouns used to describe triggers of parosmia with size representing word frequency across 375 parosmics. (B) Distribution of sentences having a negative (in red) or positive (in green) sentiment. (C) Average emotions in sentences describing parosmia episodes.

Fig. 4.

Impacts on quality of life. Percentage of respondents (A) concerned about failing to detect common hazards and (B) reporting changes in common behaviors. (C) Differences in reports of weight fluctuation compared to the anosmia/hyposmia baseline. Error bars represent bootstrapped standard errors.

Fig. 5.

Degree of severity for parosmia and phantosmia. (A) Distribution of severity scores among parosmic and phantosmic groups. Higher scores represent more frequent and/or longer episodes. (B) The severity score correlates with the reported impact of the olfactory disorder on their quality of life. Error bands represent 95% confidence intervals. Error bars represent bootstrapped standard errors.