Association of Smell Identification Deficit with Alzheimer’s Disease Assessment Scale-Cognitive Subscale, Japanese Version Scores and Brain Atrophy in Patients with Dementia

Abstract

Introduction: Olfactory dysfunction is commonly associated with Alzheimer’s disease (AD) and may be related to disorder of the central olfactory processing system. In this work, therefore, we examined the relationships between olfactory changes and the most affected cognitive domain or degree of brain atrophy in patients with AD and mild cognitive impairment (MCI). Methods: The subjects were 55 AD patients and 27 MCI patients. Smell identification tests were performed using Odor Stick Identification Test for Japanese ­(OSIT-J). The severity and nature of cognitive dysfunctions were evaluated using the AD Assessment Scale-cognitive subscale, Japanese version (ADAS-Jcog). MRI with voxel-based specific regional analysis system for AD software was used for evaluation of brain atrophy. Results: ­OSIT-J scores were significantly correlated with total ­ADAS-Jcog scores, as well as with ADAS-Jcog subscale items of word recall task, orientation (memory domain) and ideational praxis. Smell identification deficit was proportional to the degree of atrophy of the medial temporal lobe. Conclusion: Smell identification deficit in AD/MCI is strongly associated with the memory domain of cognitive function and with atrophy of the medial temporal lobe.