EAST LANSING, Mich. – A new study provides further evidence that a simple scratch-and-sniff test could predict Parkinson’s disease even earlier than previously thought.
According to Michigan State University researcher Honglei Chen, lead author and professor of epidemiology, the test could potentially identify certain people who are at an increased risk of developing the disease up to 10 years before they are actually diagnosed. Previous research has shown an association between sense of smell and disease progression of up to four to five years.
The federally funded study, now published online in Neurology, the official publication of the American Academy of Neurology, is also one of the first to follow black people.
The study also found that older men with a poor sense of smell were more likely to develop the disease compared to women.
The study included 1,510 white and 952 black participants with an average age of 75. The test asked people to smell 12 common odors including cinnamon, lemon, gasoline, soap and onion, and then select the correct answer from four choices.
Based on their scores, participants were divided into three groups – poor sense of smell, medium and good. Researchers then monitored participant health through clinical visits and phone interviews for more than a decade.
Overall, 42 people developed Parkinson’s during the study including 30 white people and 12 black people.
People with poor sense of smell were nearly five times more likely to develop the disease than people with a good sense of smell. Of the 764 people with a poor sense of smell, 26 people developed the disease, compared to just seven of the 835 people whose sense of smell was good and nine of the 863 people whose sense of smell was categorized as medium.
Researchers also discovered that the results stayed the same after adjusting for other factors that could affect risk including smoking, coffee intake and history of head injury.
“It’s important to note that not everyone with low scores on the smell test will develop Parkinson’s disease,” Chen said. “More research is needed before the smell test can be used as a screening tool for Parkinson’s, but we are definitely on to something and our goal now is to better characterize populations that are at higher risk for the disease and to identify other factors involved.”
The National Institute on Aging, National Institute of Nursing Research and National Institute of Environmental Health Sciences funded the study.