A simple new test that could be carried out at home could help detect a devastating condition as much as 20 years before symptoms start, according to breakthrough research. This smell test could indicate if someone is likely to develop Alzheimer’s disease.

Alzheimer’s disease is the most common form of dementia in the UK. In its early stages, it can cause memory lapses, which tend to get worse over time, before more severe symptoms such as delusions and mood swings develop.

Typically an Alzheimer’s diagnosis isn’t given until after symptoms start. But a study has revealed a way to predict the likelihood of the condition years in advance. 

A study, by a team at Massachusetts General Hospital in the US, found that how well we identify and remember different smells could warn us about cognitive decline. As part of their work, they developed a smell test called AROMHA that people can take at home. 

The test is simple – participants were sent cards in the post with smell-infused labels. They peel and sniff the labels while following instructions online. 

The purpose of the test is to check several smell abilities including naming odours correctly, telling different smells apart, remembering smells from earlier in the test, and rating how strong each smell seems. Researchers focused on smell due to the fact the areas of the brain that process smells are among the first hit by Alzheimer’s disease. 

In the study, they noted how these parts of the brain can develop Alzheimer’s disease changes before symptoms start. Changes can begin 15 to 20 years before memory problems appear.

The study, published in Scientific Reports, involved 187 people. This included 127 people with normal cognition, 34 people who worried about their memory but tested normally, and 19 people with mild cognitive impairment (MCI), which often precedes Alzheimer’s. 

A further seven patients who had no sense of smell were recruited as a comparison group. As reported by Study Finds, researchers found that people with mild cognitive impairment performed significantly worse on smell identification and discrimination tests compared to both healthy individuals and those with only subjective memory concerns. 

This was the case even after accounting for age, sex, and education. Performance was also consistent whether participants were observed or unobserved during testing. 

Among what were considered cognitively normal people, smell abilities naturally declined with age, but this decline was much steeper in those with cognitive impairment. Participants with diagnosed smell loss scored at chance levels, proving the test’s accuracy.

The team concluded that the AROMHA test could help predict neurodegenerative diseases. Study authors wrote: “These results suggest that the AROMHA Brain Health Test could be used in clinical research settings in different languages to explore the utility of olfactory biomarkers to predict the presence of blood-based, image-based, or cerebrospinal fluid (CSF)-based biomarkers of neurodegenerative disease and longitudinal development of clinical symptoms.”

However, it is important to note that the study had several limitations. The different groups were tested at one point in time rather than tracking individuals over years, which would better gauge how smell changes might predict cognitive decline. 

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The sample size was also small, especially for those with mild cognitive impairment. Study authors commented that further studies were needed to confirm the “predictive value” of the AROMHA test on cognitive decline.

According to the NHS, some of the early signs someone has Alzheimer’s are:

• Forgetting about recent conversations or events
• Misplacing items
• Forgetting the names of places and objects
• Having trouble thinking of the right word
• Asking questions repetitively
• Showing poor judgement or finding it harder to make decisions
• Becoming less flexible and more hesitant to try new things.

If you or someone you know is displaying symptoms, you should speak to a GP.