Long-Term Loss of Smell May Persist After COVID-19 Infection

Recent research indicates that the loss of olfactory function, or sense of smell, following COVID-19 infection can persist for years and may go unnoticed by many individuals. Utilizing a comprehensive 40-odor clinical test, scientists have found that even people who do not perceive any smell issues often exhibit measurable impairment.

Supported by the NIH's RECOVER initiative and conducted by a team across the United States, the study involved over 3,500 participants and aimed to objectively assess post-COVID olfactory dysfunction. Results showed that approximately 80% of individuals reporting changes in their sense of smell after COVID-19 scored poorly on the smell identification test conducted around two years later. Notably, nearly a quarter of this group experienced severe impairment or complete loss of smell.

Surprisingly, a significant portion—66%—of those who did not report any olfactory problems still scored abnormally low, revealing that loss of smell may be underrecognized. Experts emphasize that hyposmia, or reduced smell function, is linked to decreased quality of life, depression, weight loss, and difficulty detecting hazards like gas leaks or spoiled food. It also serves as an early sign of neurodegenerative diseases such as Parkinson’s and Alzheimer’s.

This large-scale, objective study is the first of its kind to employ formal testing to understand long-term olfactory deficits post-COVID. Researchers used the University of Pennsylvania Smell Identification Test (UPSIT), a validated scratch-and-sniff assessment, to compare individuals' olfactory performance with a control database. Findings suggest that healthcare providers should consider routine smell testing in post-COVID care to identify those at risk.

Current efforts are exploring treatments like vitamin A supplementation and olfactory training to help recover the sense of smell. A better understanding of how COVID-19 impacts the brain's sensory and cognitive systems could enhance these therapeutic strategies. However, the study notes limitations, including the absence of direct taste assessments and potential misclassification of uninfected individuals due to limited virus testing.

These findings underline the importance of recognizing and addressing olfactory dysfunction as a significant, yet often overlooked, consequence of COVID-19, with implications for long-term health and safety.

Source: https://medicalxpress.com/news/2025-09-unnoticed-loss-linger-years-covid.html