Relationship between cognitive impairment and olfactory function among older adults with olfactory impairment

Area of Science:

• Gerontology
• Neuroscience
• Ophthalmology

Background:

• Olfactory function declines with age and is an early indicator of neurodegenerative diseases like Alzheimer's and Parkinson's.
• Assessing reduced smell (hyposmia) and absence of smell (anosmia) is crucial for diagnosing neurodegenerative conditions.
• Cognitive impairment is associated with olfactory decline, highlighting the need to understand these relationships.

Purpose of the Study:

• To investigate the associations among aging, cognitive function, and olfactory abilities in individuals experiencing olfactory impairment.
• To determine if olfactory test results can help differentiate between various causes of smell dysfunction, including dementia.

Main Methods:

• An observational study involving 141 patients with olfactory deterioration.
• Patients were categorized with dementia, mild cognitive impairment (MCI), age-related hyposmia, or post-viral olfactory dysfunction (PVOD).
• Assessments included T&T olfactometry, a self-administered odor questionnaire (SAOQ), visual analog scale (VAS), and Mini-Mental State Examination.

Main Results:

• T&T odor recognition thresholds worsened with both aging and cognitive impairment.
• Patients with dementia and hyposmia exhibited the highest T&T recognition thresholds and the greatest differences between detection and recognition thresholds.
• Hyposmia associated with dementia also showed the highest SAOQ and VAS scores compared to other groups.

Conclusions:

• Investigating dementia is recommended for patients presenting with hyposmia, especially those with elevated T&T recognition thresholds.
• A significant difference between T&T detection and recognition thresholds, along with high SAOQ and VAS scores, suggests potential dementia.
• Olfactory testing can be a valuable tool in the early detection and differential diagnosis of cognitive decline.