Related Experiment Video
Updated: Sep 16, 2025
07:27
Olfactory Assays for Mouse Models of Neurodegenerative Disease
Published on: August 25, 2014
22.2K
Olfactory Impairment and Incident Cognitive Decline: A Systematic Review and Meta-Analysis
Brian Sheng Yep Yeo1, Harris Jun Jie Muhammad Danial Song1, Benjamin Kye Jyn Tan1,2,3
1Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
International Forum of Allergy & Rhinology
|July 10, 2025
Summary
Olfactory impairment (OI) significantly increases the risk of cognitive decline (CD). Assessing smell function can aid in early detection and management of cognitive issues.
Area of Science:
- Neuroscience
- Gerontology
- Epidemiology
Background:
- Olfactory impairment (OI) is linked to adverse aging outcomes.
- Cross-sectional studies show high OI prevalence in neurodegenerative diseases, but temporal links to cognitive decline (CD) are unclear.
Purpose of the Study:
- To synthesize the longitudinal association between olfactory impairment and cognitive decline.
- To evaluate olfactory impairment as a potential predictor of cognitive decline.
Main Methods:
- A systematic meta-analysis of longitudinal studies identified via PubMed, Embase, and Web of Science.
- Inclusion of studies reporting self-reported or objectively measured OI and validated CD assessments.
- Data extraction, bias assessment, and mixed-effects meta-analysis, including subgroup and sensitivity analyses.
Main Results:
- OI was associated with a 2.06-fold increased risk of any cognitive decline.
- Severe OI conferred a higher risk (RR=2.60) compared to moderate OI (RR=1.51).
- An 18% increased risk of CD per 10% decrease in olfactory score was observed, with a population-attributable fraction of 18%.
Conclusions:
- Olfactory impairment may be a significant risk factor for cognitive decline.
- OI assessment could serve as a cognitive screening tool.
- Cognitive screening is recommended for individuals with persistent olfactory impairment.
Related Concept Videos
01:25Olfaction
45.2K
The sense of smell is achieved through the activities of the olfactory system. It starts when an airborne odorant enters the nasal cavity and reaches olfactory epithelium (OE). The OE is protected by a thin layer of mucus, which also serves the purpose of dissolving more complex compounds into simpler chemical odorants. The size of the OE and the density of sensory neurons varies among species; in humans, the OE is only about 9-10 cm2.
The olfactory receptors are embedded in the cilia of the...
The olfactory receptors are embedded in the cilia of the...
45.2K
01:03Olfactory Receptors: Location and Structure
9.7K
The process of olfaction, also known as the sense of smell, is a sophisticated chemical response system. The specialized sensory neurons that facilitate this process, known as olfactory receptor neurons, are situated in an upper segment of the nasal cavity, known as the olfactory epithelium. Olfactory sensory neurons are bipolar, with their dendrites extending from the epithelium's apex into the mucus that lines the nasal cavity. Airborne molecules, when inhaled, traverse the olfactory...
9.7K
01:20Physiology of Smell and Olfactory Pathway
9.6K
Humans detect odors with the help of specialized cells located in the upper part of the nasal cavity, called olfactory receptor neurons (ORNs). ORNs possess hair-like structures called cilia, which are receptive to sensations from the inhaled air. When an odorant molecule binds to a specific receptor on the cell of the cilia, it leads to a series of events that ultimately cause the ORN to send electrical signals to the olfactory bulb in the brain through the olfactory nerves.
The olfactory...
The olfactory...
9.6K
01:26Alzheimer's Disease: Overview
675
Alzheimer's Disease (AD) is a continually advancing neurodegenerative disorder, distinguished by escalating memory loss, cognitive dysfunction, and dementia. The disease unfolds in three stages: preclinical, mild cognitive impairment (MCI), and dementia. Its onset is insidious, and the progression gradual, with the cause not well explained by other disorders.
The clinical diagnosis of AD hinges on the presence of memory and other cognitive impairments. Biomarkers, such as changes in Aβ...
The clinical diagnosis of AD hinges on the presence of memory and other cognitive impairments. Biomarkers, such as changes in Aβ...
675
01:30Cognitive Development During Adulthood
296
Cognitive development continues throughout adulthood, undergoing significant shifts across early, middle, and late stages. Individual transition occurs from adolescent idealism to pragmatic and adaptable thinking in early adulthood. During this period, individuals learn to integrate personal beliefs with the recognition that other perspectives are equally valid. Exposure to the complexities of modern society, diverse experiences, and higher education contribute to this adaptive thought process,...
296