When it comes to medications that are being designed to treat Alzheimer's disease, it is widely believed that they may only work if they're administered before dementia sets in. This means that it's vitally important to detect the onset of Alzheimer's as early as possible, and a new test could help doctors do just that. It involves getting patients to smell things.

Previous research has already suggested that a decrease in the sense of smell is linked to Alzheimer's. Led by Dr. David R. Roalf, a team from the University of Pennsylvania decided to put that theory to the test.

In order to do so, they assessed a total of 728 seniors using both the standard Montreal Cognitive Assessment test, along with the commercially available Sniffin' Sticks Odor Identification Test – in the latter, participants have to correctly identify 16 scents.

All of the seniors had been previously evaluated at the university, using "an array of neurological methods." Each one was thus placed in one of three categories: healthy older adult, mild cognitive impairment [MCI], or Alzheimer's dementia.

Based only on the cognitive test, Roalf's team was able to correctly identify approximately 75 percent of the MCI group. When the results of the sniff test were factored in, however, that amount increased to 87 percent. The MCI group is an important one, as mild cognitive impairment is known to occur a few years before actual Alzheimer's follows.

That said, combining the results of the cognitive and sniff tests also increased the accuracy of identifying subjects belonging to the other two groups.

Roalf is now trying to streamline the sniff test, so that it becomes widely adopted.

"We're hoping to shorten the Sniffin' Sticks test, which normally takes five to eight minutes, down to three minutes or so, and validate that shorter test's usefulness in diagnosing MCI and dementia," he says. "We think that will encourage more neurology clinics to do this type of screening."