Olfactory Dysfunction and Cognitive Impairment After COVID-19

BACKGROUND/AIMS:The coronavirus disease-2019 (COVID-19) pandemic has brought to mind the long-known relationship between loss of smell, cognitive functions, and neurodegenerative processes and raised the question, "Can COVID-19 trigger or accelerate the development of neurodegenerative diseases?".This study aimed to investigate cognitive functions and their relationship with loss of smell, temporal changes in cognitive functions, and factors that may have an effect on this possible change in individuals with COVID-19. MATERIALS AND METHODS:Individuals between the ages of 18-60, who had mild-moderate COVID-19 were included in the study within 3-6 months following the disease.COVID-19-related olfactory dysfunction and its duration were evaluated.Cognitive functions were assessed using the Addenbrooke's Cognitive Examination-Revised test battery and the Symbol Digit Modalities test.After six months, neuropsychological tests were repeated. RESULTS:Ninety-seven patients who had COVID-19 (52 patients with COVID-19-related loss of smell and 45 patients without) were included in the study.Fifty patients were re-evaluated 6 months after their initial examination.Loss of smell was found to be continued for 3 months in 42 patients and >3 months in 10 patients.Neuropsychological test results showed that cognitive function was affected by loss of smell at the first examination.Additionally, the cognitive impact was more pronounced in the group with >3 months of smell loss than in the group with 3 months of smell loss.Six months later, test results were better than those at the first examination in both groups, regardless of loss of smell or not. CONCLUSION:Our results indicate that cognitive function may be affected with or without loss of smell in patients with COVID-19, and that cognitive dysfunction and the duration of loss of smell may be related.It was found that cognitive functions were recovered substantially over time, and it was considered that COVID-19-related damage affecting cognitive functions was recoverable.