A new study published in JAMA Network Open shows that long term changes in the sense of smell remain a serious and often hidden consequence of COVID 19. Many people continue to experience reduced smell sensitivity even years after recovering from the infection.

The study was part of the National Institutes of Health RECOVER project, which followed more than three thousand adults across thirty five states. Researchers used a standardized test called the University of Pennsylvania Smell Identification Test to measure how well participants could recognize different odors about one point eight years after infection.

Among one thousand three hundred ninety three people who reported losing their sense of smell or taste during COVID 19, about eighty percent still had measurable loss. Even more striking, sixty six percent of those who said their smell was normal also showed mild to severe impairment when tested. This means many may have lingering smell problems without realizing it.

Hidden smell loss and brain function

People who continued to have smell loss were more likely to report problems with memory and concentration, often described as brain fog. The study supports earlier findings that the sense of smell is closely connected to areas of the brain that control memory, emotion, and decision making.

Why it matters

Smell is important for daily safety and quality of life. A reduced sense of smell can make it harder to detect smoke, spoiled food, or gas leaks, and can also lead to changes in appetite and mood. Persistent loss of smell may also be linked to cognitive changes, which researchers are continuing to study.

Who is most affected

Younger women appeared more likely to experience long term smell problems. The scents most often affected included lemon, licorice, and watermelon. The findings suggest that COVID 19 may disrupt how the brain processes pleasant and neutral smells.

What can help

Experts recommend formal smell testing for anyone who has had COVID 19, even if they believe their smell has returned. Smell training or repeatedly smelling specific scents every day can help retrain the brain and encourage recovery. Some emerging treatments such as vitamin A therapy and platelet rich plasma injections are being studied for potential benefit.

What this means for you

Even after recovery, the lingering effects of COVID 19 can quietly impact the sense of smell and possibly brain health. Regular monitoring and early rehabilitation can help detect hidden changes and improve long term quality of life.

Source

Horwitz LI, Becker JH, Huang W, et al. Olfactory Dysfunction After SARS-CoV-2 Infection in the RECOVER Adult Cohort. JAMA Netw Open. 2025;8(9):e2533815. doi:10.1001/jamanetworkopen.2025.33815