Olfactory impairment remains three years after COVID-19

Olfactory dysfunction (OD) is recognized as one of the major sequelae of SARS-CoV-2 infection, and previous studies have shown that smell loss in COVID-19 patients can persist for more than two years after onset. However, it remains unclear whether SARS-CoV-2–related dysosmia can last even longer. In this three-year follow-up study, epidemiological, demographic, clinical, and odor test data were collected from 155 recovered COVID-19 patients and 170 healthy controls across multiple centers. The Toyota-Takagi (T&T) olfactometry scoring system was used as an auxiliary diagnostic tool for dysosmia, and emotional status and sleep conditions were also assessed. Correlation analysis and logistic regression were conducted to identify influential factors for OD. More than 30% of participants experienced emotional and sleep disturbances, which were more common among women and older individuals. Insomnia (AIS > 6) and anxiety (HAMA ≥ 7) were identified as risk factors for OD in recovered COVID-19 patients. At the three-year follow-up, seven patients (4.5%), all older than 50 years, continued to experience smell loss. These findings suggest that a significant proportion of patients suffer from persistent OD, which may be associated with long-term COVID-19 sequelae or neurodegenerative conditions.