Connecting the Dots: Loss of Smell and Alzheimer's 5 Risk Unveiled -written by Poonam Chanchlani (BCA, Data Science)

A new study has shed light on the intriguing connection between the loss of smell (anosmia) and the progression of Alzheimer's disease-related cognitive impairment. This research, focusing on older adults living outside of nursing homes, reveals that a diminished sense of smell may be a key early indicator of Alzheimer's and the accumulation of harmful brain proteins like amyloid-beta and tau. The findings, led by scientists from the National Institute on Aging (NIA), were recently published in the Journal of Alzheimer's Disease.
 

The Missing Link:  Smell and Alzheimer's :

While the loss of smell had previously been identified as an early warning sign for Alzheimer's in both human and animal studies, its association with the advancement of dementia-related brain changes had not been extensively studied among larger populations of older adults until now. In this comprehensive study, a group of 364 participants from the renowned Baltimore Longitudinal Study of Aging (BLSA) were tracked over an average period of approximately 2.5 years. The BLSA, led by the NIA, is a long-standing investigation of healthy aging in the United States.
 

Key Insights :

At the outset, all participants were cognitively normal and underwent baseline cognitive assessments, odor identification tests, and PET scans—an advanced brain imaging technique for detecting Alzheimer's and related dementias' hallmark deposits of amyloid-beta and tau. During the study's duration, 17 participants, equivalent to 5% of the total group, were diagnosed with mild cognitive impairment (MCI), with 11 of these cases linked to Alzheimer's disease.

 

The research team uncovered a significant correlation: for every point decrease in odor identification test performance, there was a 22% higher likelihood of developing MCI. This connection remained robust even after adjusting for various factors like age, gender, race, education, genetics, smoking, depression symptoms, and vascular disease. The PET brain scans of these participants painted a telling picture—lower olfactory scores aligned with higher levels of Alzheimer's pathology in the brain, especially in regions associated with the sense of smell and critical areas tied to memory and learning.

 

These findings strongly suggest that a decline in the sense of smell is intimately linked to the extent and progression of neuropathological damage observed in Alzheimer's disease. It underscores why a diminished sense of smell can serve as an early red flag for Alzheimer 's-related MCI. The researchers aim to delve further into whether olfactory function can predict other types of dementia-related neurodegenerative changes.

This groundbreaking research was made possible with support from the Intramural Research Program grant Z01-AG000015-57 and NIA grant P30AG066507, aligning with NIA's AD+ADRD Research Implementation Milestone 9.M, "Develop diagnostics/biomarkers in asymptomatic individuals."

 

Reference : Tian, Qu et al. Olfaction, cognitive impairment, and PET biomarkers in community-dwelling older adults. Journal of Alzheimer's Disease.