The relationship between olfaction and cognitive function in the elderly

• Published in: The journal of physiological sciences Vol. 70; no. 1; p. 48
• Main Authors: Uchida, Sae, Shimada, Chiho, Sakuma, Naoko, Kagitani, Fusako, Kan, Akiko, Awata, Shuichi
• Format: Journal Article
• Language: English
• Published: Japan Springer 14.10.2020; BioMed Central
• Subjects: Aged; Aged, 80 and over; Alzheimer's disease; Basal forebrain; Cholinergic transmission; Cognitive ability; Cognitive Dysfunction - epidemiology; Cognitive Dysfunction - physiopathology; Data analysis; Dementia; Female; Forebrain; Humans; Identification; Japan - epidemiology; Male; Neuropsychological Tests; Odor thresholds; Older people; Olfaction; Olfaction Disorders - epidemiology; Olfaction Disorders - physiopathology; Olfactory thresholds; Psychologists; Short Communication; Japan; Elderly people; Cognitive function; Odor identification threshold; Olfactory function; Attention
• ISSN: 1880-6546; 1880-6562
• DOI: 10.1186/s12576-020-00777-8

This study investigated the relationship between olfaction and cognitive function in 12 elderly people (age: 80.9 ± 1.6) living in the community. Olfactory function was assessed by the identification threshold for rose odor. Four cognitive measures consisting general cognitive ability assessed by Mini-Mental State Examination (MMSE), its sub-domains, and attentional ability assessed by drawing a line to connect the numbers consecutively (trail-making test part A; TMT-A), were assessed. Subjects with a higher olfactory threshold (≥ 5) declined more in the performance speed of TMT-A (73% ± 7%, p = 0.05) compared with those subjects with a lower threshold (≤ 4) (averaged value was set at 100%). Other cognitive statuses assessed by MMSE tended to decline in subjects with higher thresholds. Because attentional function relates to the basal forebrain cholinergic system, our results suggest that olfactory impairment links to the decline in cognitive function, particularly of attention-relating cholinergic function.