Testing Someone’s Sense of Smell May Help Predict Alzheimer’s

Doctors could soon be able to diagnose early Alzheimer’s disease using a simple sniff test.

The disease, which is the most common type of dementia, affects 850,000 people in the UK.

Scientists have found increasing evidence that a person’s sense of smell sharply decreases in the early stages of Alzheimer’s and now a new study has shown that a simple sniff test could help the accuracy of diagnosing the awful disease.

The research comes from the Perelman School of Medicine at the University of Pennsylvania and has also shown that a sniff test can also prove useful in the detection of another pre-dementia condition, Mild Cognitive Impairment (MCI) which frequently develops into Alzheimer’s dementia within a few years.

Neurology experts have been keen to discover novel ways of identifying people who are at high risk of Alzheimer’s but do not show any signs. Particularly as there is a widespread belief that Alzheimer’s medications currently being developed may not work after dementia has set it.

David R. Roalf, PhD, an assistant professor in the department of Psychiatry at Penn said: “There’s the exciting possibility here that a decline in the sense of smell can be used to identify people at risk years before they develop dementia.”

The researchers used a simple over the counter test available in the US to test subjects ability to identify 16 different odours. They used this test, along with the Montreal Cognitive Assessment, to 728 elderly people.

The participants were assessed by doctors using a mixture of different methods at the medical school and placed into one of three categories: “healthy older adult”, “mild cognitive impairment”, or “Alzheimer’s dementia.”

Roalf and his team then used the results from the cognitive test alone, or combined them with the sniff test, to see how well they identified the patients in each section.

The researchers say that the results showed that the sniff test added significant accuracy to a diagnosis, when combined with the cognitive test.

For example, a cognitive test on it’s own identified 75 per cent of people with MCI, but that percentage was raised to 87 per cent when the results of a sniff test were added.

The scientists say that combining the results of the sniff test meant more accurate identification of healthy older adults and those suffering Alzheimer’s dementia and it even boosted the accuracy of diagnosing patients with milder or more advanced categories of MCI.

Roalf said: “These results suggest that a simple odour identification test can be a useful supplementary tool for clinically categorising MCI and Alzheimer’s, and even for identifying people who are at the highest risk of worsening.”

Some doctors in larger dementia clinics in America have already started using the sniff tests as part of their investigations, but have reported that the practise hasn’t become widespread because the most useful tests take too long to do.

The researchers at Penn are now trying to develop a quicker test that works just as well as the longer ones.