Smell Test, Brief Cognitive Screen Combo May Help Rule Out Dementia

Damian McNamara

November 01, 2019

Performance on two quick tests ― a cognitive screen and an olfactory test ― may rule out future dementia, including Alzheimer disease (AD), for patients with mild memory problems, results of a large follow-up study show.

Investigators found that of those participants whose scores on both the Brief Smell Identification Test (B-SIT) and the Blessed Orientation Memory Concentration Test (BOMC) indicated that they were unimpaired, 96.5% did not develop dementia during an average follow-up of 4 years.

"The take-home message for neurologists and other physicians is that if a brief cognitive test is supplemented by a brief olfaction test like the B-SIT, and if a patient with memory complaints scores well on both tests, it is not necessary to investigate further," lead author D. P. Devanand, MD, professor of psychiatry and neurology and director of geriatric psychiatry at Columbia University Medical Center in New York City, told Medscape Medical News.

This approach could reduce the need for position-emission tomographic imaging or lumbar puncture to identify for biomarkers of AD, he said.

The study was published online October 29 in Alzheimer's and Dementia.

Five-Minute Smell Test

In previous cross-sectional studies, researchers demonstrated that an inability to identify odors helped distinguish older adults who were cognitively intact from others who had mild cognitive impairment (MCI) or AD. In addition, prior work examined how combining odor identification with a brief cognitive test can help differentiate people with MCI or AD from control persons.

However, the researchers note that the "utility of intact performance on brief odor identification and global cognitive tests in predicting lack of cognitive decline or conversion to AD has not been examined explicitly."

To investigate this, the investigators assessed 749 participants with MCI from the Washington Heights/Inwood Columbia Aging Project. The cohort did not have dementia at baseline.

Participants completed the University of Pennsylvania Smell Identification Test (UPSIT) and the BOMC. The B-SIT smell test is a 12-item component of UPSIT. The B-SIT score ranges from 0 (no odor correctly identified) to 12 (a perfect score). The B-SIT and the BOMC each take approximately 5 minutes to administer.

During the follow-up, 15% of the 749 participants who completed at least one subsequent assessment transitioned to dementia. The majority of these 109 patients, 101 people, developed AD dementia.

The remaining eight participants developed other cognitive impairments, including Lewy body dementia and vascular dementia.

In terms of predictors, a lower B-SIT score at baseline was significantly associated with transition to dementia when researchers controlled for age, sex, language, and education (hazard ratio [HR], 2.25; 95% confidence interval [CI], 1.12 – 4.49; P = .02). Worse performance on the BOMC was likewise a significant predictor (HR, 5.64; 95% CI, 3.49 – 9.12; P < .0001).

When the investigators combined both BOMC and B-SIT results and controlled for the same factors, they found that worse BOMC performance (HR, 5.60; 95% CI, 3.47 – 9.05) and worse B-SIT scores (HR, 2.25; 95% CI, 1.10 – 4.60) each predicted a greater likelihood that a person would transition to dementia. Both these factors were significant (P < .0001 and P = .03, respectively).

Interestingly, there was no significant interaction between the two predictors.

For the prediction of AD, "very similar results were found to those for dementia," the researchers note. "The need to assess both olfaction and global cognition is highlighted by the weaker predictions for only one of these two measures."

After a patient passes both tests, "the clinician can choose to inform the patient that, at this time, the likelihood of Alzheimer's disease is extremely low based on the test results," said Devanand, who is also a research psychiatrist at the New York State Psychiatric Institute, New York City.

"The patient can be asked to come back for repeat evaluation in a year only if they feel that their memory or other cognitive ability is worsening further," he said.

The findings, the investigators note, "confirm that olfactory sensory impairment, particularly early in the course of dementia, is a salient marker of cognitive decline and future dementia."

Future studies to confirm the results are warranted, Devanand said. "From a research perspective, the results need to be confirmed in other community-based cohorts.

"From a clinical perspective, we need to administer these brief tests to patients in broader clinical settings, particularly primary care, to evaluate if the results remain valid in that setting. We are currently in the process of doing such a study that is funded by the National Institute of Aging," he said

One Piece of the Puzzle?

Commenting on the study for Medscape Medical News, Rebecca Edelmayer, PhD, director of scientific engagement at the Alzheimer's Association, described the findings as "very interesting" but cautioned against relying on performance on these two tests in clinical practice until further validation studies have been conducted.

"At this point, it's too preliminary. It's one research study in one population. These are early days for using odor to indicate cognitive decline." However, she added, "the study is still very exciting."

The research is part of a bigger picture of a "blossoming field" regarding the detection of early disease, she added.

In the future, predicting who will progress to dementia or AD could become more sensitive by combining sensory markers such as olfaction and vision, functional indicators, including gait and cadence, and speech, language, and cognitive changes, she said.

Grants from the National Institutes of Health National Institute on Aging (NIA) funded the study. Devanand is a consultant to Eisai, Avanir, Acadia, Genentech, Neuronix, and Grifols and has received NIA research support. Edelmayer has disclosed no relevant financial relationships.

Alzheimers Dement. Published online October 29, 2019. Abstract

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