You may have heard that if a loved one has a failing sense of smell, he or she is headed for Alzheimer's disease. Not necessarily true, according to a new report in the journal The Laryngoscope.
Dr. Mehmet Oz, for example, offers an Alzheimer's smell test on his website, probably based on earlier research suggesting a link between a difficulty in identifying scents like banana and cinnamon to the presence of Alzheimer's lesions in the brain. Clinicians have sometimes used smell tests as part of a clinical assessment, although they're not among the key tests used to diagnose Alzheimer's.
The new study, conducted by Robert Wood Johnson Foundation Clinical Scholars at the University of Michigan and the VA Center for Clinical Management Research, is the first systematic review of the quantity and quality of so-called olfactory identification tests as prognostic tools for Alzheimer's. The authors reviewed nearly 1,200 articles dating back to 1984.
Although the team found evidence that loss of smell is associated with Alzheimer's, there's not enough proof to conclude that loss of smell is a predictor for developing the disease, reports Medical News Today. The researchers note that several different medical problems are also associated with loss of smell. There are also several other possible explanations for an association between smell changes and dementia, such as age or dehydration.
"A nonspecific association between poor smell function and Alzheimer's dementia is not the same as actually being able to use a smell test to predict Alzheimer's," says Gordon Sun, a general otolaryngologist at the University of Michigan. "This study helps set the record straight about where the evidence currently stands."
He adds: "Understandably, researchers, clinicians, and the public are eager for a simple, accurate, and inexpensive way to predict or diagnose Alzheimer's early -- but we're not there yet."
Not by a nose.