Olfactory Dysfunction in Alzheimer’s Disease: The Clinical Characteristics and Cortical Thickness Alterations

Abstract Background Olfactory dysfunction (OD) is reported as a useful predictor for Alzheimer’s disease (AD). There are three sub-domains of olfaction: olfactory threshold, discrimination and identification. In AD patients, whether the performance of three sub-domains has different influential factors or relates to specific brain magnetic resonance imaging (MRI) change is not clear. Methods We recruited 105 typical AD patients, assessed patients’ cognitive function, neuropsychiatric symptoms and activity of daily living by related scales, evaluated patients’ olfactory function by Sniffin’ Sticks test and measured patients’ cortical thicknesses by MRI. Results Olfactory threshold negatively correlated with AD patients’ age and positively related to cognitive function; olfactory discrimination positively related to patients’ cognitive function and cortical thickness of left lateral orbitofrontal gyrus; olfactory identification positively related to patients’ cognitive function and cortical thicknesses of left medial orbitofrontal gyrus, left middle temporal gyrus and bilateral superior temporal gyrus. Conclusions The three sub-domains of olfaction in AD patients have different influential factors: age influences olfactory threshold and cognitive function influences all three olfactory sub-domains. The performance of olfactory discrimination and identification in AD patients was associated with the cortical thickness of orbitofrontal gyrus and temporal lobe.