Loss of smell during COVID linked to structural, functional brain alterations

Many individuals who lost their sense of smell when infected with COVID-19 show structural and functional brain alterations on imaging, according to new work published in Nature. 

Near the onset of the pandemic, when tests for the virus varied in their reliability and a COVID diagnosis was a nearly automatic isolation sentence, anosmia became a telltale sign of infection. According to data shared by the Centers for Disease Control and Prevention last year, around 34% of patients who contracted COVID between 2020 and 2023 reported losing their sense of smell. 

Now, experts are concerned that the symptoms could be associated with long-term brain alterations. In a group of people who reported anosmia as one of their COVID symptoms, experts recently observed an association between the loss of smell and decreased functional activity during decision-making tasks, reduced cortical thickness and other neural measures. These findings indicate that patients who report issues with smell during a bout with COVID may need additional, targeted follow-up, the group suggested. 

“This symptom can serve as a clinical, and in some cases a preclinical, indicator of neurological diseases such as Alzheimer’s disease, Huntington’s disease, Parkinson’s disease, vascular dementia, and mild cognitive impairment, among others,” co-corresponding author Pablo Billeke, with the Laboratory of Neuroscience and Neuromodulation in Santiago, Chile, and colleagues explain. “Therefore, objective evaluations and follow-up are required.”