Symptoms of Dementia: Study Finds Inability to Smell Peppermint Linked to Disease

Updated | Alzheimer's is the sixth leading cause of death in the United States, with an annual research budget of around $480 million, according to the Alzheimer's Association. But the "holy grail" of contemporary dementia research is determining the risk factors that make people more likely to develop the disease, neurologist Ronald Petersen, who directs the Alzheimer's Disease Research Center and Study of Aging at the Mayo Clinic, tells Newsweek.

Risk factor research is just as important as treatment development, Petersen says, since the two work together: first detection and then prevention. Once viable pre-dementia medications are found, doctors can use them in the intervention stage, similar to how cholesterol drugs lower heart disease risk.

Part of diagnosing patients early comes down to spotting warning signs and testing, which can be costly. According to the Alzheimer's Association, there is no one single test used to detect the disease (the most common form of dementia). Meanwhile, MRI scans are not feasible for every patient as they frequently cost thousands of dollars.

A team of researchers from the University of Chicago say their new research may help solve this problem by providing a simple and affordable test that detects dementia risk. In a large sample of nearly 3,000 adults ages 57 to 85 years old, researchers looked at whether a decline in our sense of smell could determine dementia diagnosis. Previous research has shown that tangles—twisted fibers of a protein that are characteristic of Alzheimer's—can be found in the olfactory system and that dementia is linked to a decrease in this sense.

Related: Alzheimer's test: Artificial intelligence spots symptoms years before doctors

In the study, people sniffed five different odors: peppermint, fish, orange, rose and leather. These were taken from a larger test used to evaluate sense of smell. In a five-year follow up, people who couldn't physically detect even one of the scents all had dementia. Almost 80 percent of those who only detected one or two scents had also been diagnosed with the disease.

Study author Dr. Jayant Pinto, tells Newsweek the findings are important because they show that the central nervous system warns us about potential health dangers. Furthermore, no one pays nearly enough attention to the power of our noses. "The sense of smell is a little bit of an ignored sense," Pinto says.

So, does this mean that a potential dementia test comes down to whether you can smell a piece of gum?

Dr. Mony de Leon, director of the Center for Brain Health at NYU Langone Health, expressed his ambivalence about the study's implications. "In general terms, it seems pretty interesting.... What's really most important in this study is the sample size. This must make it the largest study of its kind."

But after analyzing the data, he suggests researchers did a better job of predicting who wouldn't get dementia.

"It's good, but it's not yet ready for prime time," de Leon says of the study.

Petersen agrees the research is well-done, but says that, on its own, it won't be used in the doctor's office. However, coupled with other tests analyzing factors such as gait and vision, which previously have been researched for their association with dementia, the new finding could be invaluable.

"Simple, cheap screening measures might separate people into high, medium and low risk," he says. "These combinations are giving you real, predictive values that are going to be useful."

This story has been updated to include quotes from Dr. Mony de Leon.