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Smell: This is often one of the first senses to be impacted by Alzheimer's disease. The individual may experience either confusion as to what they smell or a lack of sensory capability. It is important if caring for an individual living alone, to keep the refrigerator and cupboards clear of outdated and spoiled food.'s Aug 7, 2019    Click to view.

Olfaction as an early marker of Parkinson's disease and Alzheimer's disease.


Olfactory impairment is a common and early sign of Parkinson's disease (PD) and Alzheimer's disease (AD), the two most prevalent neurodegenerative conditions in the elderly. This phenomenon corresponds to pathologic processes emerging in the olfactory system prior to the onset of typical clinical manifestations. Clinically available tests can establish hyposmia through odor identification assessment, discrimination, and odor detection threshold. There are significant efforts to develop preventative or disease-modifying therapies that slow down or halt the progression of PD and AD.

Loss of smell linked to Alzheimer’s cognitive impairment and biomarkers. NIH Link to Studies
The findings provide additional evidence that loss of smell (known as anosmia) is a key early sign of Alzheimer's-related cognitive impairment and the accumulation of associated harmful proteins, such as amyloid-beta and tau. The research, led by NIA scientists, was published in the Journal of Alzheimer's Disease. May 19, 2022

Decline in sense of smell had previously been confirmed as an early warning sign for Alzheimer’s in both human and animal studies, but its connection to the uptick of dementia-related brain imaging biomarkers over time had not been as closely studied in larger populations of older adults. For this study, the team tracked 364 participants from the Baltimore Longitudinal Study of Aging (BLSA) over an average period of about 2.5 years. The NIA-led BLSA is the longest running study of healthy aging in America.

Reference: Tian, Qu et al. Olfaction, cognitive impairment, and PET biomarkers in community-dwelling older adults. Journal of Alzheimer’s Disease. 2022;86(3):1275-1285. doi: 10.3233/JAD-210636.
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