Acute loss of smell is one of the most common symptoms of COVID-19, but for two decades it has been linked to other illnesses, including Parkinson’s disease and dementia. Now, a bad sense of smell may mean a higher risk of pneumonia in the elderly, according to a team of researchers from Michigan State University.
“About a quarter of adults 65 or older have a bad sense of smell,” said Honglei Chen, a professor in the Department of Epidemiology and Biostatistics at MSU College of Human Medicine. “Unlike a visual or hearing impairment, this sensory deficit has been largely overlooked; more than two-thirds of people with a bad sense of smell don’t know they have it.”
In a one-of-a-kind study, Chen and his team found a possible link between a bad sense of smell and a higher risk of hospitalization for pneumonia. They analyzed 13 years of health data from 2,494 seniors, aged 71 to 82, from the metropolitan areas of Pittsburgh, Pennsylvania, and Memphis, Tennessee. This study aimed to examine whether a poor sense of smell in the elderly is associated with a higher future risk of developing pneumonia.
Chen’s research was recently published in the journal The Lancet Healthy Longevity. Participants were given a brief odor identification test, or B-SIT, using common smells such as lemons and gasoline to determine if their smell was good, moderate, or weak. Then, participants were followed for the next 13 years using clinical exams and follow-up phone calls to identify hospitalization due to pneumonia.
The researchers found that compared to participants who had a good smell, participants with a bad smell were about 50% more likely to be hospitalized with pneumonia at any time during the 13-year follow-up. Among participants (with poor sense of smell) who had never had pneumonia before, the risk of having the very first pneumonia was about 40% higher.
“To our knowledge, this study provides the first epidemiological evidence that poor olfaction (sense of smell) is associated with a higher long-term risk of pneumonia in the elderly,” said Yaqun Yuan, postdoctoral fellow at Chen’s research group.
This study provides new evidence that a bad sense of smell may have broader health implications beyond its links to Parkinson’s disease and dementia.
“This is just one example of how little we know about this common sensory deficit,” Chen said. “Whether as a risk factor or as a marker, a bad sense of smell in the elderly can herald multiple chronic diseases beyond what we know of. We have to think outside the box.
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Material provided by University of Michigan. Original written by Emilie Lorditch. Note: Content can be changed for style and length.