Can Your Sense of Smell Predict Parkinson's Disease?

Many people are aware of the classic symptoms of Parkinson's disease, such as tremors, muscle rigidity, slowed movement, and compromised posture and balance. But did you also know that a reduced or altered sense of smell is often one of the first signs of the disease?

According to scientists at Northwestern University's Feinberg School of Medicine and Northwestern Memorial Hospital, many people with Parkinson's disease recall that they lost their sense of smell before any of their other symptoms became apparent. So the researchers are working to study the correlation between olfactory loss and Parkinson's disease as well as determine if loss of smell might be a tool in early detection. Northwestern, along with at least a dozen other centers, is participating in the Parkinson's Associated Risk Study (PARS), a long-term study of the relatives of people who have the disease. Study subjects are given scratch-and-sniff tests along with questionnaires that help the researchers make associations between any loss of smell and the development of the disease.

Parkinson's disease, which affects nearly a million people in this country alone, is an incurable condition that can, to a certain extent, be managed with medication. It occurs when brain cells that produce dopamine, a chemical responsible for communication between nerve cells and smooth muscle movement, age prematurely and die. The result is an inability to control one's movements, along with other symptoms such as olfactory loss. Unfortunately, by the time most people are diagnosed with Parkinson's, some 60 percent to 80 percent of the dopamine-producing cells in their brain have been destroyed. Scientists hope that early detection of the condition-such as with a smell test-will enable the disease take a slower course or perhaps even prevent it from developing at all.

Interestingly, not all smells are created equal when it comes to Parkinson's patients. In a study at the University of Pennsylvania, 26 people with the disease and 26 people without the disease were exposed to 40 different smells. On the whole, the Parkinson's patients were better at identifying lemon but were less able than the others to identify licorice, coconut, banana, pickle, paint thinner, turpentine, cherry, and soap. The scientists also discovered that the less able the Parkinson's patients were to identify these odors, the less dopamine activity they had in their brains.


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