Sociodemographic Characteristics and Comorbidities of Patients With Long COVID and Persistent Olfactory Dysfunction

Importance: Determining the characteristics, type, and severity of olfactory dysfunction in patients with long COVID is important for the prognosis and potential treatment of the affected population. Objective: To describe the sociodemographic and clinical features of patients with long COVID who develop persistent olfactory dysfunction. Design, Setting, and Participants: This cross-sectional study, conducted at a rehabilitation center at a public university in the Amazon region of Brazil between September 9, 2020, and October 20, 2021, comprised 219 patients with long COVID and self-reported neurologic symptoms. Of these 219 patients, 139 received a diagnosis of chronic olfactory dysfunction, as confirmed by the Connecticut Chemosensory Clinical Research Center (CCCRC) test. Exposure: Clinical diagnosis of long COVID. Main Outcomes and Measures: Electronic case report forms were prepared for the collection of sociodemographic and clinical data. Patients' sense of smell was evaluated via a CCCRC test, and the association of olfactory dysfunction with aspects of daily life was recorded using a questionnaire. Results: Of the 219 patients included in the study, 164 (74. 9%) were women, 194 (88. 6%) were between 18 and 59 years of age (mean SD age, 43. 2 12. 9 years), 206 (94. 1%) had more than 9 years of education, and 115 (52. 5%) had a monthly income of up to US 192. 00. In the study group, 139 patients (63. 5%) had some degree of olfactory dysfunction, whereas 80 patients (36. 5%) had normosmia. Patients with olfactory dysfunction had a significantly longer duration of long COVID symptoms than those in the normosmia group (mean SD, 242. 7 101. 9 vs 221. 0 97. 5 days; P =. 01). Among patients with anosmia, there was a significant association between olfactory dysfunction and daily activities, especially in terms of impairment in hazard detection (21 of 31 patients 67. 7%), personal hygiene (21 of 31 patients 67. 7%), and food intake (21 of 31 patients 67. 7%). Univariable logistic regression analyses found that ageusia symptoms were associated with the occurrence of olfactory dysfunction (odds ratio OR, 11. 14 95% CI, 4. 76-26. 07; P <. 001), whereas headache (OR, 0. 41 95% CI, 0. 22-0. 76; P <. 001) and sleep disorders (OR, 0. 48 95% CI, 0. 26-0. 92; P =. 02) showed an inverse association with the occurrence of olfactory dysfunction. Conclusions and Relevance: Olfactory dysfunction is one of the most important long-term neurologic symptoms of COVID-19, with the highest prevalence seen among women, adults, and outpatients. Patients with olfactory dysfunction may experience persistent severe hyposmia or anosmia more than 1 year from the onset of symptoms, suggesting the possibility of the condition becoming a permanent sequela.