Olfactory Threshold Test as a Quick Screening Tool for Cognitive Impairment: Analysis of Two Independent Cohorts

Article type: Research Article

Authors: Gao, Yang^{a; b} | Liu, Yanchao^c | Zhang, Yao^d | Wang, Yuying^a | Zheng, Jie^e | Xu, Zhipeng^f | Yu, Haitao^a | Jin, Zetao^a | Yin, Yin^a | He, Benrong^a | Sun, Fei^a | Xiong, Rui^a | Lei, Huiyang^a | Jiang, Tao^a | Liang, Yi^b | Ke, Dan^a | Zhao, Shi^g | Mo, Wen^h | Li, Yanni^h | Zhou, Qiuzhi^a | Wang, Xin^a | Zheng, Chenghongⁱ | Zhang, Huaqiu^c | Liu, Gongping^a | Yang, Ying^a | Wang, Jian-Zhi^{a; j; *}

Affiliations: [a] Department of Pathophysiology, School of Basic Medicine, Ministry of Education Key Laboratory for Neurological Disorders, Hubei Key Laboratory for Neurological Disorders, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China | [b] Department of Radiology, Wuhan Brain Hospital, Wuhan, China | [c] Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China | [d] Li-Yuan Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China | [e] Neuroscience Research Institute and Department of Neurobiology, School of Basic Medical Sciences, Peking University; Key Laboratory for Neuroscience, Ministry of Education/National Health Commission, Peking University, Beijing, China | [f] Department of Neurology, Zhongnan Hospital of Wuhan University, Wuhan, China | [g] Department of Endocrinology, the Central Hospital of Wuhan, Wuhan, China | [h] Health Service Center of Jianghan District, Wuhan, China | [i] Department of Endocrinology, Wuhan Hospital of Traditional Chinese Medicine, Wuhan, China | [j] Co-innovation Center of Neuroregeneration, Nantong University, Nantong, China

Correspondence: [*] Correspondence to: Jian-Zhi Wang, Department of Pathophysiology, School of Basic Medicine, Ministry of Education Key Laboratory for Neurological Disorders, Hubei Key Laboratory for Neurological Disorders, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China. Tel./Fax: +86 27 83693883; E-mail: wangjz@mail.hust.edu.cn.

Abstract: Background:Olfactory dysfunction appears prior to cognitive decline, and thus it has been suggested to be an early predictor of Alzheimer’s disease. However, it is currently not known whether and how olfactory threshold test could serve as a quick screening tool for cognitive impairment. Objective:To define olfactory threshold test for screening cognitive impairment in two independent cohorts. Methods:The participants are comprised of two cohorts in China, 1,139 inpatients with type 2 diabetes mellitus (T2DM, Discovery cohort) and 1,236 community-dwelling elderly (Validation cohort). Olfactory and cognitive functions were evaluated by Connecticut Chemosensory Clinical Research Center test and Mini-Mental State Examination (MMSE), respectively. Regression analyses and receiver operating characteristic (ROC) analyses were carried out to determine the relation and discriminative performance of the olfactory threshold score (OTS) regarding identification of cognition impairment. Results:Regression analysis showed that olfactory deficit (reducing OTS) was correlated with cognitive impairment (reducing MMSE score) in two cohorts. ROC analysis revealed that the OTS could distinguish cognitive impairment from cognitively normal individuals, with mean area under the curve values of 0.71 (0.67, 0.74) and 0.63 (0.60, 0.66), respectively, but it failed to discriminate dementia from mild cognitive impairment. The cut-off point of 3 showed the highest validity for the screening, with the diagnostic accuracy of 73.3% and 69.5%. Conclusion:Reducing OTS is associated with cognitive impairment in T2DM patients and the community-dwelling elderly. Therefore, olfactory threshold test may be used as a readily accessible screening tool for cognitive impairment.

Keywords: Cut-off value, mild cognitive impairment, olfactory function, type 2 diabetes mellitus

DOI: 10.3233/JAD-230023

Journal: Journal of Alzheimer's Disease, vol. 93, no. 1, pp. 169-178, 2023