Summary: A massive NIH-backed study reveals that COVID-19’s toll on smell may be more widespread and lasting than most realize. Even patients without noticeable symptoms often performed poorly on scent tests, raising safety and health concerns. Because smell loss can signal deeper neurological issues, experts are calling for routine testing and exploring new treatments.
If you think your sense of smell hasn’t been the same since having COVID-19, you’re probably right. A new study that used an objective 40-odor identification test found that many people continue to experience lingering smell problems long after infection — even when they don’t realize it.
Researchers with the National Institutes of Health’s RECOVER initiative, supported by NYU Langone Health’s Clinical Science Core, examined how COVID-19 might be connected to hyposmia (the medical term for reduced ability to smell).
Lingering Loss of Smell Common in COVID Survivors
The study found that 80% of people who said their sense of smell had changed after COVID-19 scored poorly on a clinical smell test taken about two years later. Nearly one in four of them were either severely impaired or had completely lost their ability to smell.
Even more striking, 66% of participants who had tested positive for COVID-19 but did not report any smell issues also showed abnormally low results.
“Our findings confirm that those with a history of COVID-19 may be especially at risk for a weakened sense of smell, an issue that is already underrecognized among the general population,” said study co-lead author Leora Horwitz, MD, of NYU Grossman School of Medicine.
Horwitz noted that even among those who had never been infected, 60% performed below normal on the same test, suggesting smell loss could be more widespread than previously thought.
Why a Reduced Sense of Smell Matters
Smell plays a vital role in daily safety and well-being. People with hyposmia may struggle to notice hazards such as spoiled food, gas leaks, or smoke. The condition is also associated with weight loss, depression, and reduced quality of life. In addition, loss of smell can sometimes serve as an early warning sign for neurodegenerative diseases like Parkinson’s and Alzheimer’s, both of which affect brain regions tied to scent processing.
Most previous studies on smell loss after COVID-19 relied on people’s own reports, which can be unreliable. To overcome that, the team used a standardized clinical tool called the University of Pennsylvania Smell Identification Test (UPSIT).
In this scratch-and-sniff test, participants identified 40 different scents by choosing from multiple-choice answers. Each correct response earned one point, and the total score was compared to data from thousands of healthy volunteers of the same sex and age. Participants were then classified as having normal, mild, moderate, severe, or complete smell loss.
The study included 3,535 adults and was published online on September 25 in JAMA Network Open. According to the authors, it is the largest investigation so far to assess long-term smell loss after COVID-19 using an objective method.
A Closer Look at the Research
Along with Horwitz, Jacqueline Becker, PhD at Icahn School of Medicine at Mount Sinai in New York is co-lead author. Hassan Ashktorab, PhD, at Howard University in Washington, D.C.; Andrea Foulkes, ScD, at Massachusetts General Hospital in Boston; and Joyce Lee-Iannotti, MD, at the University of Arizona in Phoenix, are study co-senior authors.
For the investigation, the research team assessed thousands of Americans who had participated in the RECOVER adult study, a multicenter analysis designed to shed light on the long-term health effects of the coronavirus. Throughout the study, those with and without a history of COVID-19 completed surveys about their symptoms every 90 days from October 2021 through June 2025.
To measure olfactory function, the team used a clinical tool: the University of Pennsylvania Smell Identification Test (UPSIT). In this scratch-and-sniff evaluation, which is considered the gold standard of its kind, participants were asked to identify 40 scents by selecting the right multiple-choice option for each odor. A correct answer earned one point, and the total UPSIT score was compared with a database of thousands of healthy volunteers of the same sex and as. Based on the results, smelling ability was characterized as normal, mildly impaired, moderately impaired, severely impaired, or lost altogether.
“These results suggest that health care providers should consider testing for loss of smell as a routine part of post-COVID care,” said Horwitz. “While patients may not notice right away, a dulled nose can have a profound impact on their mental and physical well-being.”
Experts are now exploring ways to restore smelling ability after having COVID-19, such as vitamin A supplementation and olfactory training to “rewire” the brain’s response to odors. Having a deeper understanding of how the coronavirus affects the brain’s sensory and cognitive systems may help refine these therapies, notes Horwitz.
Study Limitations and Funding
Horwitz cautions that the study team did not directly assess loss of taste, which often accompanies problems with smell. In addition, it is possible that some uninfected participants were misclassified due to the lack of universal testing for the virus. This may help explain the surprisingly high rate of hyposmia identified in those without a supposed history of COVID-19, she says.
Funding for the study was provided by National Institutes of Health grants R01HL162373, U01DC019579, OT2HL161847, OT2HL161841, and OT2HL156812.
Other NYU Langone researchers involved in the study are Gabrielle Maranga, MPH, and Jennifer Frontera, MD.
Other study authors are Alexander Charney, MD, PhD, and Juan Wisnivesky, MD, DrPH, at the Icahn School of Medicine at Mount Sinai; Weixing Huang, MSPH, Mark Albers, MD, PhD, and Christina Sorochinsky at Massachusetts General Hospital; Dara Adams, M.D., and Jerry Krishnan, MD, PhD, at the University of Illinois Chicago; Sarah Donohue, PhD, MPH, at the University of Illinois in Peoria; Mirna Ayache, MD, Brian D’Anza, MD, and Grace McComsey, MD, at Case Western Reserve University in Cleveland, Ohio; Jasmine Berry, MPH, Tiffany Walker, MD, and Zanthia Wiley, MD, at Emory University in Atlanta; and Hassan Brim, PhD, and Adeyinka Laiyemo, MD, at Howard University.
Additional study authors are Tanner Bryan, MS, at Denver Health in Colorado; Robert Clark, MD, Mark Goldberg, MD, and Thomas Patterson, MD, at the University of Texas at San Antonio; Melissa Cortez, DO, and Torri Metz, MD, at the University of Utah in Salt Lake City; Nathaniel Erdmann, MD, PhD, Valerie Flaherman, MD, MPH; and Emily Levitan, ScD, at the University of Alabama at Birmingham; Tamara Fong, MD, PhD; at Harvard Medical School in Boston; Jason Goldman, MD, MPH, at Providence Swedish Medical Center in Seattle; Michelle Harkins, MD, at the University of New Mexico in Albuquerque; Sally Hodder, MD, at West Virginia University in Morgantown; Vanessa Jacoby, MD, John Daniel Kelly, MD, Jeffrey Martin, MD, MPH; Megumi Okumura, MD; and Michael Peluso, MD, at the University of California San Francisco; Prasanna Jagannathan, MD, Xiaolin Jia, MD, and Andre Kumar, MD, at Stanford University in California; Kathryn McCaffrey, MD, and Helen Nguyen, DO, at the University of Washington in Seattle; Ganesh Murthy, MD, at the University of Arizona in Phoenix; Sairam Parthasarathy, MD, at the University of Arizona in Tucson; Samuel Parry, MD, at the University of Pennsylvania in Philadelphia; and Samantha Wiegand, MD, at Miami Valley Hospital in Dayton, Ohio.
Other study collaborators are RECOVER community health advocates Teresa Akintonwa, MA, and Maxwell Hornig-Rohan; and Hannah Davis at the Patient-Led Research Collaborative in New York City.
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Materials provided by NYU Langone Health / NYU Grossman School of Medicine. Note: Content may be edited for style and length.