Persistent olfactory dysfunction as an indicator of cognitive impairment in long COVID-19 syndrome: implications for monitoring and rehabilitation.

Abstract

Background: Persistent olfactory dysfunction (OD) and cognitive impairment are among the most frequently reported sequelae of long term infection with SARS-CoV-2 (long COVID-19). However, the association between these conditions remains unclear. This study investigated the correlation between OD and cognitive impairment in patients recovering from COVID-19 to identify the implications for therapeutic and rehabilitation strategies.

Materials and methods: A cross-sectional study of adult patients diagnosed with long COVID was conducted at a healthcare centre in Brazil. Olfactory function was assessed using the Connecticut Chemosensory Clinical Research Centre (CCCRC) test, and cognitive performance was evaluated using the Montreal Cognitive Assessment (MoCA). Statistical analyses included odds ratios (OR) and linear regression to explore the association between OD severity and cognitive scores, adjusting for potential confounders such as age, sex, and comorbidities.

Results: A total of 241 patients (age: 48.60 ± 12.68 years; 73% female) were included. Cognitive impairment (MoCA < 23) was present in 64% of the participants. OD was identified in 92% of the patients and ranged from mild to anosmia. Linear regression analysis showed a weak yet statistically significant correlation between the CCCRC and MoCA scores (R = 0.14, p = 0.02). An OR of 2.87 (95% CI: 1.57-5.25, p = 0.00) indicated higher odds of cognitive impairment in patients with severe OD.

Discussion: This study supports the hypothesis that there is a weak yet significant association between OD and cognitive impairment in patients with long COVID. These findings underscore the importance of early screening for olfactory dysfunction as a potential marker of cognitive monitoring and the need for intervention in this population.