In fact, one study has found that not being able to smell certain scents could be a sign that someone is at high risk of Alzheimer's disease.

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The researchers behind the study say it could help link anosmia—or the medical term for the loss of smell—with the onset of Alzheimer's.

This makes sense because it's known that the olfactory bulb (involved with the sense of smell) and the entorhinal cortex (involved with memory and naming of odors) are among the first brain structures first to be affected by the disease.".

"This means that a simple smell test may potentially be able to give us information about the progression of the disease that is similar to the much more invasive and expensive tests of the cerebrospinal fluid that are currently being used," John Breitner, MD, the director of the Centre for Studies on Prevention of Alzheimer's Disease at McGill University and the study's co-author, said in a statement.

"If we can delay the onset of symptoms by just five years, we should be able to reduce the prevalence and severity of these symptoms by more than 50 percent." But, he still cautioned: "Problems identifying smells may be indicative of other medical conditions apart from [Alzheimer's disease] and so should not be substituted for the current tests.".

"We think a decline in the ability to smell, specifically, but also sensory function more broadly, may be an important early sign, marking people at greater risk for dementia," he told Medical News Today.

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