Prevalence and Correlates of Parosmia and Phantosmia among Smell Disorders

Abstract

Among those many individuals who suffer from a reduced odor sensitivity (hyposmia/anosmia) some individuals also experience 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 suffered from post-viral olfactory loss (p < 0.001), while phantosmia occurred most frequently in middle-aged respondents (p < 0.01) and was more likely to be caused by head trauma than parosmia (p < 0.01). A higher prevalence of odor distortion was observed 3 months to a year after their olfactory symptom onset (p < 0.001), which coincides with the timeline of physiological recovery. Additionally, we observed that the frequency and duration of distortions negatively affects 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.

Parosmia as a predictor of a better olfactory function in COVID-19: a multicentric longitudinal study for upper respiratory tract infections

“…Our observations for C19 patients having a better odour threshold in the second visit, a higher proportion of clinically relevant threshold improvement and, therefore, tended to have a higher TDI-score at the second visit might reflect the hypothesis that parosmia is caused due peripheral damage [ 11 , 44 ] and could be a sign of regeneration [ 45 ]. Previous data showed the temporal relationship between regeneration and parosmia approximately 3–12 months after the onset of symptoms [ 14 ]. Moreover, the higher difference in threshold could underline the peripheral origin of parosmia and its activity at the level of the olfactory epithelium.…”

“…Qualitative OD is most commonly present along with smell loss due to—in descending frequency URTI, TBI, idiopathic OD, or sinonasal causes [ 12 , 13 ]. Qualitative OD in C19 and other causes is associated with poorer quality of life [ 14 , 15 ]. Interestingly, some studies showed an association of parosmia with better olfactory recovery [ 16 , 17 ].…”

Increasing incidence of parosmia and phantosmia in patients recovering from COVID-19 smell loss

“…If we are highly conservative and assume all of the individuals who did not respond to our follow up survey recovered, we calculate 50% (smell long haulers) of 30% (response rate), resulting in ~2.7 million Americans and ~15 millions worldwide may be smell long-haulers. Present data suggest ~47% of smell long-haulers report parosmia, which would translate to over a million Americans (and over 7 million worldwide) with parosmia as a result of COVID-19.While olfactory symptoms may be formally classified as mild outcomes by some health authorities, the possibility that millions of individuals may experience long term anosmia and parosmia as a consequence of prior COVID-19 infection is highly concerning, given the downstream impacts this will likely have on dietary habits 38 , quality of life 39 , and mental health 40 . We also find that smell long-haulers report other post-acute sequelae of COVID-19.…”