Multicentre study on the course of non-sinunasal olfactory disorders

ABSTRACT

The COVID-19 pandemic continues to keep the world on tenterhooks with increasing numbers of infections and at the same time increasing cases of post-viral olfactory dysfunction. In 5 to 20 % of those affected, loss of smell persists after 1 to 2 months. In a multicentre study (n= 652, of which 404 were women), non-sinunasal, acquired olfactory disorders of different entities were considered postviral 584 of which 490 after COVID-19 infection, idiopathic 28, traumatic 40. There was an overall olfactory improvement over 3.5 (± 1.2) months for threshold, discrimination and identification (t > 3.65;p < 0.001) for all olfactory disorders studied. When analyzed separately for COVID-19 infection, other postviral olfactory disorders showed initially poorer olfactiory function (M = 23.6 vs. 26.5;t = 2.9;p = 0.01), but showed comparable improvement over time (F = 0.05;p = 0.83). Patients with parosmia showed better olfaction (M = 23.2 vs. 25.1;t = 2.5;p = 0.02), but not in the subgroup analysis after COVID-19 infection. At the first visit after 4.1 ( ± 3.3) months after acute COVID 21% patients were normosmotic;at the second visit after a further 3.6 ( ± 1.5) months, 34% of patients had normosmia after COVID-19 infection. During the course, an improvement in the ability to smell was demonstrable. For many patients with COVID-19-associated olfactory loss, an improvement that is experienced as complete may only occur over the course of months and possibly years.