A simple odor identification test combined with a brief cognitive assessment for cognitive decline and dementia showed similar predictive power to amyloid PET imaging in a large longitudinal study. The findings suggest this low-cost, non-invasive approach could be an effective screening tool to identify individuals at risk of dementia.
In the Mayo Clinic Study of Aging (MCSA) cohort of 647 cognitively unimpaired or mildly impaired older adults followed for an average of 8.1 years, the combination of the 12-item Brief Smell Identification Test (BSIT) and Blessed Information Memory Concentration Test (BIMCT) demonstrated strong predictive utility for cognitive decline that was comparable to Pittsburgh Compound B (PiB) amyloid PET imaging. The study, led by Davangere P. Devanand, MD, of Columbia University, was published in Alzheimer's & Dementia.
During follow-up, 102 study participants developed cognitive decline and 34 developed dementia. In individual predictor models, PiB PET showed the most robust prediction of cognitive decline, but impaired BSIT, impaired BIMCT, and neuroimaging measures were also significant predictors. The combination of demographics, BSIT, and BIMCT showed similar predictive utility to demographics and PiB PET, and combining all measures provided the best prediction.
By 7.5 years of follow-up, 75% of participants impaired on BSIT, BIMCT, and PiB showed cognitive decline, compared to only 2% of those unimpaired on all three measures.
The study has several strengths, including its large sample size, long follow-up period, and comprehensive assessment of multiple biomarkers. However, limitations include the predominantly white study population and relatively low rate of progression to dementia.
Dr. Devanand and colleagues noted that while brief cognitive tests like the BIMCT lack the robust predictive utility of more comprehensive neuropsychological testing, they offer considerable practicality due to their brevity and ease of administration.
The findings align with previous research showing odor identification deficits predict cognitive decline and dementia. Olfactory impairment in Alzheimer's disease is thought to reflect tau pathology in olfactory processing regions.
"Combining these measures that shared limited common variance improved predictive utility at a relatively early stage of disease progression," the authors wrote. They added that examining non-linear effects of continuous measures and comparing to emerging plasma biomarkers are important areas for future research.
A conflict of interest disclosure statement can be found in the study.