Adams et al. (2018) - NSHAP study, ~2,906 adults aged 57-85, published in Journal of the American Geriatrics Society - found older adults with olfactory dysfunction were twice as likely to develop dementia within 5 years.
NIA/BLSA Study (2022) - Baltimore Longitudinal Study of Aging, 364 participants, published in Journal of Alzheimer's Disease - linked smell decline to faster buildup of amyloid-beta and tau pathology on brain scans.
Laukka et al. (2023) - SNAC-K study with 2,473 dementia-free participants followed for 12 years found olfactory dysfunction significantly increased dementia risk, with complete loss of smell showing an even stronger association, published in Alzheimer's & Dementia.
APOE ε4 genetic study - Identified that carriers of this Alzheimer's risk gene show earlier decline in odor identification ability.
Devanand et al. (2015) - Community-based research demonstrating olfactory deficits as a predictor of cognitive decline and Alzheimer's dementia, published in Neurology.
I'm also looking at a meta-analysis synthesizing findings across multiple studies to establish the broader pattern.
2025 SNAC-K follow-up - A 12-year population-based study examining how isolated and combined olfactory and cognitive impairments develop over time.
UChicago research - Found that accelerated smell loss over time correlates with cognitive decline and measurable changes in brain structure.
2024 meta-analysis - Reviewing the current evidence on olfactory dysfunction's role in mild cognitive impairment and Alzheimer's disease progression.