A waning sense of smell among older adults may portend frailty as they age, according to research published January 10 in The Journals of Gerontology. The researchers say the association is independent of the link between waning olfaction and a greater risk for dementia and Alzheimer’s disease.
Although everyone will experience some loss of smell as they age, marked declines could predict a host of problems beyond just a harder time smelling the roses.
“The sensory loss is more than just annoying,” said Nicholas Rowan, MD, of the Departments of Otolaryngology–Head and Neck Surgery and Neurological Surgery at the Johns Hopkins School of Medicine in Baltimore. “It may be an indicator of future untoward outcomes.”
Frail individuals face a higher risk than others of developing chronic diseases such as hypertension, chronic kidney disease, and rheumatoid arthritis.
Rowan and colleagues analyzed data from 1,160 men and women in the National Social Life, Health, and Aging Project, which explores factors that affect the health of Americans as they age. The average age of the study participants was 76 years, 56% were women, and approximately 40% were frail, as determined from measures such as a 10% or greater decline in weight over 5 years, taking at least 17 seconds to rise from a chair, or limited physical activity (engaging in physical activity no more than three times) in the preceding month.
The researchers correlated two tests of how well people could smell — whether they were able to identify odors at increasingly potent concentrations (olfactory identification), and whether they could distinguish between different odors (olfactory sensitivity) — with their degree of frailty. The olfactory identification test included six concentrations, while the olfactory sensitivity test included five scents.
On average, participants could identify more than 4 of the 5 odors (average, 4.17; standard deviation). [SD], 1.02) and could detect more than three odors in ascending concentrations (3.52; SD, 1.45). These numbers were lower for the frailest individuals, however (3.88 and 3.15, respectively), according to the researchers.
“Frailty means that older people are less resilient in the face of stressors,” said Honglei Chen, MD, PhD, the Foundation Professor of Epidemiology and Biostatistics at Michigan State University. This is why especially frail individuals are less likely to respond well to unexpected health challenges.
Chen was not involved in Rowan’s study but conducted a study that was published in Annals of Internal Medicine In 2019 that showed a link between an especially poor sense of smell in older adults and premature death.
Chen noted that approximately 25% of older adults have a poor sense of smell — although most will say their sense of smell is fine if asked.
“Oftentimes people are unaware of it,” Rowan added.
Both Chen and Rowan emphasized the need for objective tests of how well people can smell, similar to vision or hearing tests, rather than relying on self-reports.
An Olfactory Legacy of COVID-19
Less attention has been paid to loss of smell in older adults than has been given to vision or hearing. Loss of smell can be gradual, which Chen said might be one reason people don’t notice they can’t smell as vividly as they’re used to. Compared to treating poor vision or hearing, clinicians have fewer ready options for improving olfaction, Rowan noted.
The COVID-19 pandemic has shifted the calculus. One common symptom of COVID is the sudden loss of smell. An increased focus on the health implications of smell and its physiologic underpinnings could be one of the “silver lining” of the pandemic, Chen said.
If an objective test shows that an older person’s sense of smell has deteriorated, Rowan said, a clinician could consider ordering a full exam to determine their degree of frailty. Anyone who is frail or at risk of becoming so could then begin a customized plan that might include an exercise program or changes to their diet.
Olfactory training, a technique used by some patients with COVID-19, has shown some promise in restoring the sense of smell by exposing people to different scents. The technique could also be used with older patients, Rowan said. Ideally, an improved sense of smell may contribute to better overall health as people age, a question Rowan said he plans to explore.
Rowan and Chen report no relevant financial relationships.
J Gerontoll. Published online December 22, 2022. Abstract
Marcus A. Banks, MA, is a journalist based in New York City who covers health news with a focus on new cancer research. His work appears in Medscape, Cancer Today, The Scientist, Gastroenterology and Endoscopy News, Slate, TCTMD, and Spectrum.
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