My father always hated chocolate, and so did I. No Snickers bars or chocolate chip cookies for us. Then at Christmas two years ago, Dad ate a piece of chocolate cake. “This is great,” he said happily as I watched in amazement. Mom later told me he had become less picky about what he ate. She didn’t think he had much of a sense of smell left either.
I hadn’t given this much thought until I saw the March 22nd post on Brainblog about a Rush University Medical Center study that showed “impaired odor identification in old age is associated with impaired global cognition and more rapid decline in perceptual processing speed and episodic memory.” The blog’s author, a neuropsychologist named Anthony Risser, suggested I contact the University of Pennsylvania’s Smell and Taste Center for more information on how loss of the sense of smell may be related to Alzheimer’s and other dementias.
Richard Doty, PhD is a Professor at the University’s School of Medicine and Director of the Center. He co-authored a recent article about a study in which a brief 10-smell test was effective in predicting whether patients with “mild cognitive impairment” would develop Alzheimer’s Disease.
Richard Doty, PhD
Why are sense of smell and cognitive decline linked? “There is no consensus as to the reasons for the smell loss in AD [Alzheimer’s disease],” Dr. Doty says, “although AD-related neuropathology does show up relatively early in such structures as the olfactory bulb and anterior olfactory nucleus.”
Just because Dad couldn’t detect odors very well didn’t necessarily mean he had or would develop Alzheimer’s. Many factors, including illnesses other than Alzheimer’s, habits such as smoking, and even normal aging can diminish our ability to smell. So smell tests can’t be used to diagnose Alzheimer’s or other dementias, but they could be useful for identifying patients whose mild memory problems may develop into more serious dementia.
When Dad first complained of memory problems several years ago, I don’t think any of his doctors asked him about his sense of smell. I looked at the American Academy of Neurology practice guidelines for early detection of dementia and also at an American Academy of Family Physicians publication about early diagnosis of dementia . Neither document says anything about smell tests.
I asked Dr. Doty why doctors wouldn’t routinely use these tests for preliminary dementia screening. I wondered whether the tests are too expensive or time-consuming. It turns out Dr. Doty is involved with Sensonics , a company that manufactures smell test kits that could be used to screen for likelihood of developing dementia. “The 12-item test takes about 5 minutes,” he said. “The cost of this test is $12.95 and it would seem to me reasonable for screening purposes. But despite a relatively large literature on olfaction in the prediction of AD, there are few clinics that use such testing.”
Dr. Doty is sending me some smell kits so I can see what the tests are like. I’ll write more about this topic once I’ve tried them out.