Home-based smell test shows promise in detecting early cognitive decline, study finds

A new study published in Scientific Reports suggests that a simple, self-administered smell test taken at home could help identify older adults who may be at risk for Alzheimer’s disease. Researchers found that older individuals with mild cognitive impairment performed significantly worse on tests of smell identification and discrimination than their cognitively healthy peers. These differences were detectable using a new digital tool called the AROMHA Brain Health Test, which participants completed remotely using scratch-and-sniff cards and a web-based app.

The researchers behind the study wanted to explore whether subtle changes in a person’s sense of smell might offer a window into early brain changes that occur before memory problems become apparent. They designed the test to be cost-effective, easy to use at home, and available in both English and Spanish. By comparing results from healthy adults, individuals with subjective memory complaints, and people with diagnosed mild cognitive impairment, the team found that smell test scores declined not only with age but also with increasing levels of cognitive difficulty.

Mild cognitive impairment is a clinical stage between normal aging and more serious decline such as dementia. People with this condition often notice changes in memory or thinking but can still function independently in daily life. However, they are more likely to go on to develop Alzheimer’s disease than those without such symptoms. The researchers were interested in identifying noninvasive ways to detect early changes in the brain, particularly those that occur before symptoms become severe. Since certain brain areas related to smell are affected early in Alzheimer’s disease, the team focused on olfaction—our sense of smell—as a potential early indicator of cognitive decline.

To investigate this, the researchers developed the AROMHA Brain Health Test, a bilingual (English and Spanish) home-based test that evaluates different aspects of smell, including odor identification, memory, discrimination, and intensity. Participants used peel-and-sniff cards mailed to their homes and completed the test online using a web application. The platform guided users through a series of steps, asking them to smell each odor, select the correct name from four options, rate its intensity, and indicate their confidence in each answer. Additional tasks required them to recall previously presented odors and to decide whether pairs of smells were the same or different.

The study included 127 cognitively normal participants, 34 with subjective cognitive complaints, and 19 with mild cognitive impairment. Participants were recruited from 21 states and Puerto Rico through research registries and online postings. Some participants were classified based on formal cognitive testing from the Massachusetts Alzheimer’s Disease Research Center, while others were categorized based on self-reported memory concerns or a physician’s diagnosis. All participants gave informed consent and completed the test either under observation (via video call or in-person) or independently.

The researchers examined how participants performed on the different components of the smell test. They found that scores on odor identification, odor discrimination, and odor memory declined with age. Importantly, individuals with mild cognitive impairment scored significantly lower on odor identification and discrimination compared to those who were cognitively normal, even after accounting for age, sex, and education. These results suggest that the smell test can detect subtle cognitive differences associated with early stages of decline.

Interestingly, the test was equally effective whether participants were observed or completed it on their own. This supports the idea that the tool can be used reliably in a home setting without the need for supervision. The researchers also compared results between English- and Spanish-speaking participants and found no meaningful differences in performance, highlighting the test’s potential for use in diverse populations.

To validate the test’s ability to detect genuine smell impairments, the researchers included a small group of individuals diagnosed with anosmia, or complete loss of smell. As expected, this group performed at chance level across all measures, confirming that the test could distinguish between normal and impaired olfactory function.

Among the older participants, the researchers divided the group into three categories: cognitively normal, those with subjective memory concerns, and those with mild cognitive impairment. They found that those with mild impairment performed significantly worse than both of the other groups on several measures, particularly odor identification and discrimination. These differences were not explained by age alone, suggesting that cognitive impairment itself was responsible for the lower scores.

One feature of the test that the researchers highlighted was the inclusion of a confidence rating after each identification task. This allowed them to measure not only whether participants chose the correct answer, but also whether they were guessing. The results showed that when participants were more confident in their answers, they were more likely to be correct—but this pattern was weaker in those with cognitive impairment. This finding supports previous research suggesting that people with early cognitive decline may overestimate their abilities or be less aware of their errors.

While the results are promising, the study had some limitations. Not all participants underwent full neuropsychological assessments, which means that some classifications were based on self-report rather than clinical testing. The study was also cross-sectional, meaning it looked at participants at a single point in time. Future studies will need to follow participants over months or years to determine whether low scores on the smell test predict future memory decline or the development of Alzheimer’s disease.

Despite these limitations, the researchers see strong potential for the AROMHA Brain Health Test as a scalable, noninvasive screening tool. It could help identify individuals who may benefit from further testing or who might be eligible for clinical trials targeting early-stage Alzheimer’s. Because the test can be administered at home and in multiple languages, it may help reach populations that are often underrepresented in research.

“Early detection of cognitive impairment could help us identify people who are at risk of Alzheimer’s disease and intervene years before memory symptoms begin,” said study author Mark Albers, a neurologist at Massachusetts General Hospital and assistant professor at Harvard Medical School. Albers was involved in founding the company that developed the Aromha Brain Health Test

The researchers plan to continue studying the test in larger and more diverse groups. They are also interested in exploring how the results relate to brain imaging or blood-based biomarkers of disease. If validated in future studies, this type of smell test could become a valuable tool for early detection and monitoring of brain health in aging adults.

The study, “Early detection of cognitive impairment could help us identify people who are at risk of Alzheimer’s disease and intervene years before memory symptoms begin,” was authored by Benoît Jobin, Colin Magdamo, Daniela Delphus, Andreas Runde, Sean Reineke, Alysa Alejandro Soto, Beyzanur Ergun, Sasha Mukhija, Alefiya Dhilla Albers, and Mark W. Albers.