Olfaction and Alzheimer Disease

Associations Between Cognitive Function, Depression, and Olfactory Function in Elderly People With Dementia in Korea

Early detection is important for delaying or preventing cognitive impairment. Since olfactory dysfunction and depression are common symptoms of cognitive dysfunction, they may serve as measurable risk indicators. This study was designed to identify the relationship between olfaction, depression, and each domain of cognitive function in elderly dementia patients in South Korea. Study participants were 108 patients who visited the outpatient clinic between March and September 2019. More significant impairment of olfactory function was found in those with mild (7.48 ± 1.28) or moderate (7.37 ± 2.22) test scores of the Expanded Clinical Dementia Rating (CDR) scale than in those with questionable scores (20.58 ± 6.18). The language domain of cognitive function, age, and education level showed 39.2% explanatory power for olfactory function (F = 5.591, p < 0.001). It is expected that assessment of olfactory function in elderly people can lead to the early detection, diagnosis, and treatment of dementia. Furthermore, it is important for future studies to confirm the relationship between each domain of cognitive function and olfactory function according to the type of dementia and to establish criteria for screening dementia in order to utilize olfactory function as a clinical marker.

The Association between Olfactory Function and Cognitive Impairment in Older Persons with Cognitive Impairments: A Cross-Sectional Study

Olfactory function is an emerging topic of research in the fields of cognitive impairment and neurodegenerative diseases. We aimed to confirm the association between olfactory function and cognitive impairment by assessing the olfactory function of older persons with cognitive impairment and identify whether olfactory function is associated with cognitive impairment. For this study, we recruited 117 older people aged ≥65 years with cognitive impairments from a public hospital in Korea. We used the Korean version of the expanded clinical dementia rating scale to evaluate participants’ cognitive impairments, and the University of Pennsylvania’s smell identification test to assess their olfactory function. Our results indicate a significant negative correlation between olfactory function and all domains of cognitive impairment (memory, orientation, judgement and problem-solving, community affairs, home and hobbies, and personal care). In addition, olfactory function was a factor associated with cognitive impairment in older persons. Therefore, we expect that our results to provide useful data for the development of interventions using olfactory stimulation to improve cognitive function in older persons with cognitive impairment.