The Effects of Brain Magnetic Resonance Imaging Indices in the Association of Olfactory Identification and Cognition in Chinese Older Adults

Abstract

BackgroundOlfactory identification dysfunction frequently occurs in individuals with cognitive decline; however, a pathological mechanism linking the two has not been discovered. We aimed to study the association between olfactory identification and cognitive function, and determine the effects of brain regions atrophy therein.MethodsA total of 645 individuals (57.5% were female) from the Taizhou Imaging Study, who underwent cognitive and olfactory identification measurements, were included. A subsample of participants underwent brain magnetic resonance imaging (n = 622). Cognition was assessed with a neuropsychological battery. Olfactory identification was measured using a 12-item Sniffin’ Sticks test. Beta and logistic regressions were used to elucidate the association between olfactory identification and cognition, and the effects of brain regions atrophy in this association.ResultsDementia was diagnosed in 41 (6.4%) individuals (mean age = 64.8 years), and mild cognitive impairment (MCI) in 157 (24.3%) individuals (mean age = 64.4 years). Olfactory identification was associated with MMSE and MoCA (both P < 0.001) and specific cognitive domains (memory, executive function, visuospatial function, and language; all P < 0.05). Higher olfactory identification was associated with lower likelihood of MCI and dementia (P < 0.05). The amygdala volume was significantly related to olfactory identification, MMSE, MoCA, and language, and could attenuate the association between olfactory identification and cognitive function.ConclusionThe association between olfactory identification and cognition can be partly attributable to differences in amygdala volume, suggesting that the amygdala could be a shared neural substrate that links olfactory identification and cognitive function. Limitations of this study include that all these results were based on a cross-sectional study.

Olfactory function, neurofilament light chain, and cognitive trajectory: A 12‐year follow‐up of the Shanghai Aging Study

“…Previous studies also found significant relationships between olfaction and neurodegenerative indicators, such as brain atrophy and hypometabolism, total tau protein (t‐tau), and NfL. Olfactory scores were found to be associated with magnetic resonance imaging‐measured volumes, mainly in AD‐signature regions, such as hippocampal, temporal lobe, entorhinal regions, and amygdala 6,14–17,43 . In addition, hypometabolism in olfactory regions, measured by fluorodeoxyglucose positron emission tomography, was also shown to have a significant association with odor identification scores 15 .…”

“…Olfactory scores were found to be associated with magnetic resonance imagingmeasured volumes, mainly in AD-signature regions, such as hippocampal, temporal lobe, entorhinal regions, and amygdala. 6,[14][15][16][17]43 In addition, hypometabolism in olfactory regions, measured by fluo-rodeoxyglucose positron emission tomography, was also shown to have a significant association with odor identification scores. 15 Longitudinally, higher olfactory scores were related to slower brain atrophy in the entorhinal cortex and hippocampus.…”

Olfactory function changes and the predictive performance of the Chinese Smell Identification Test in patients with mild cognitive impairment and Alzheimer's disease

“…Even altered olfactory identification function has been detected in subjective cognitive decline (SCD), a stage that occurs before MCI (Jobin et al, 2021b ). A recent study provided evidence that the amygdala (a component of the POC) functions as a shared neural substrate linking olfactory identification ability with cognitive function (Shao et al, 2021 ; Tan et al, 2022 ). Olfactory identification deficits were also detected in both AD and MCI.…”