Researchers say the inability to smell things like lemons and onions can predict Parkinson’s by as much as 10 years before other symptoms appear.

Your sense of smell may be an accurate predictor of Parkinson’s disease up to a decade before other symptoms appear.

New research published today in the journal Neurology concluded that poor sense of smell in adults is associated with greater risk of the disease.

Researchers utilized a popular scratch and sniff test called the Brief Smell Identification Test (BSIT).

They found that individuals with low scores on this exam had a higher prevalence of Parkinson’s disease.

During the BSIT, individuals are asked to use a multiple choice format to identify 12 common odors, including lemon, gasoline, onion, and cinnamon.

Individuals were separated into three groups based on their scores, representing poor, medium, and good sense of smell.

In all, 1,510 Caucasians and 952 African-Americans, with an average age of 75, took the test.

Participants were followed for 10 years.

Of that group, 42 developed Parkinson’s disease. Thirty of those individuals were Caucasian and 12 were African-American.

Researchers discovered that people who did poorly on the scratch and sniff test were almost five times more likely to develop the disease than those with higher scores.

There were 26 cases of Parkinson’s disease in the poor sense of smell group, compared with nine in the medium group, and seven in the group with the best sense of smell.

“A poor sense of smell may predict the risk of Parkinson’s disease up to a decade, and this is particularly true for white men,” Dr. Honglei Chen, a study author and professor of epidemiology and biostatistics at the Michigan State University College of Human Medicine, told Healthline.

“Research on olfactory impairment may eventually help us identify high risk populations and understand how Parkinson’s disease develops in the first place,” he added.

The study also noted several other factors that affect risk of developing the disease.

Although black patients were more likely to have poor sense of smell compared with their white counterparts, they were less likely to have Parkinson’s disease.

The link between poor sense of smell and the disease was also clearer in men than in women.

Although researchers admit that there must be further investigation into how an olfactory test could be used to diagnose people with Parkinson’s, this could still be an important step forward.

Previous smell test associations with Parkinson’s disease only predicted it within four or five years.

Chen concluded that this test can actually predict the disease significantly earlier than that.

Time is a significant factor in Parkinson’s diagnosis, before symptoms manifest.

“Parkinson’s disease often takes decades to develop, and at the time of Parkinson’s clinical diagnosis, it is too late to stop or slow down the disease process,” said Chen.

There are no lab tests for Parkinson’s disease.

The difficulty in diagnosing it has prompted researchers to look at new and innovative ways to predict it.

A team at RMIT University in Australia showed off a new diagnostic tool earlier this month that was touted as being 93 percent accurate in predicting the disease before any symptoms were present.

The test involves analyzing speed and pen pressure while people draw spiral shapes.

Despite the promise of these predictive tools, neither the RMIT test or the smell test is yet available for use among the general public.