Qiang Wang1,2, Ben Chen1, Xiaomei Zhong1, Huarong Zhou1, Min Zhang1, Naikeng Mai3, Zhangying Wu1, Xingxiao Huang1, Antje Haehner4, Xinru Chen1, Lavinia Alberi Auber5,6, Qi Peng1, Thomas Hummel4, Yuping Ning1,7,8. 1. Memory Clinic, Department of Geriatric Psychiatry, The Affiliated Brain Hospital of Guangzhou Medical University (Guangzhou Huiai Hospital), Guangzhou, Guangdong Province, China. 2. Department of Geriatric Psychiatry, The Second People's Hospital of Dali Bai Autonomous Prefecture, Dali, Yunnan Province, China. 3. Department of Neurology, The Affiliated Brain Hospital of Guangzhou Medical University (Guangzhou Huiai Hospital), Guangzhou, Guangdong Province, China. 4. Smell and Taste Clinic, Department of Otorhinolaryngology, Technische Universität Dresden, Germany. 5. Department of Medicine, University of Fribourg, Fribourg, Switzerland. 6. Swiss Integrative Center of Human Health, Fribourg, Switzerland. 7. The first School of Clinical Medicine, Southern Medical University, Guangzhou, Guangdong Province, China. 8. Guangdong Engineering Technology Research Center for Translational Medicine of Mental Disorders, Guangzhou, China.
Abstract
BACKGROUND: Odor identification dysfunction occurs early in Alzheimer's disease (AD) and is considered a preclinical symptom along with subjective cognitive decline (SCD). Nevertheless, whether subjects with SCD are co-symptomatic with odor identification dysfunction remains unclear. OBJECTIVE: To compare the degree of odor identification dysfunction and assess the relation between odor identification and cognitive performance in the AD spectrum (including SCD, mild cognitive impairment (MCI), and AD). METHODS: Patients (84 SCD, 129 MCI, 52 AD) and 35 controls underwent the Sniffin' Sticks Screen 16 test and comprehensive neuropsychological examination. RESULTS: Odor identification scores were progressively lower moving from normal older adult to SCD, MCI, and AD. Additionally,the proportion of odor identification dysfunction were increasingly higher in the AD spectrum (p for trend <0.001), but no significant difference was found in the proportion of subjective olfactory dysfunction. No significant correlation was found between odor identification and cognition in the normal older adults and SCD subjects, but odor identification correlated with global cognition in the MCI (r = 0.199, p = 0.033) and in the AD (r = 0.300, p = 0.036) patients. Multiple linear regression showed that odor identification dysfunction was most strongly associated with memory among different cognitive subdomains and was most strongly associated with immediate verbal recall among different memory subdomains. CONCLUSION: Odor identification dysfunction is already present with SCD and deepens with disease severity in the AD spectrum, and it may contribute to predicting cognitive decline and identifying SCD subjects who are at risk of developing AD.
BACKGROUND: Odor identification dysfunction occurs early in Alzheimer's disease (AD) and is considered a preclinical symptom along with subjective cognitive decline (SCD). Nevertheless, whether subjects with SCD are co-symptomatic with odor identification dysfunction remains unclear. OBJECTIVE: To compare the degree of odor identification dysfunction and assess the relation between odor identification and cognitive performance in the AD spectrum (including SCD, mild cognitive impairment (MCI), and AD). METHODS:Patients (84 SCD, 129 MCI, 52 AD) and 35 controls underwent the Sniffin' Sticks Screen 16 test and comprehensive neuropsychological examination. RESULTS: Odor identification scores were progressively lower moving from normal older adult to SCD, MCI, and AD. Additionally,the proportion of odor identification dysfunction were increasingly higher in the AD spectrum (p for trend <0.001), but no significant difference was found in the proportion of subjective olfactory dysfunction. No significant correlation was found between odor identification and cognition in the normal older adults and SCD subjects, but odor identification correlated with global cognition in the MCI (r = 0.199, p = 0.033) and in the AD (r = 0.300, p = 0.036) patients. Multiple linear regression showed that odor identification dysfunction was most strongly associated with memory among different cognitive subdomains and was most strongly associated with immediate verbal recall among different memory subdomains. CONCLUSION: Odor identification dysfunction is already present with SCD and deepens with disease severity in the AD spectrum, and it may contribute to predicting cognitive decline and identifying SCD subjects who are at risk of developing AD.