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Kovalová M, Gottfriedová N, Mrázková E, Janout V, Janoutová J. Cognitive impairment, neurodegenerative disorders, and olfactory impairment: A literature review. OTOLARYNGOLOGIA POLSKA 2024; 78:1-17. [PMID: 38623856 DOI: 10.5604/01.3001.0053.6158] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/17/2024]
Abstract
<br><b>Introduction:</b> The early detection and diagnosis of dementia are of key importance in treatment, slowing disease progression, or suppressing symptoms. The possible role of changes in the sense of smell is considered with regard to potential markers for early detection of Alzheimer's disease (AD).</br> <br><b>Materials and methods:</b> A literature search was conducted using the electronic databases PubMed, Scopus, and Web of Science between May 30, 2022 and August 2, 2022. The term "dementia" was searched with keyword combinations related to olfaction.</br> <br><b>Results:</b> A total of 1,288 records were identified through the database search. Of these articles, 49 were ultimately included in the analysis. The results showed the potential role of changes in the sense of smell as potential biomarkers for early detection of AD. Multiple studies have shown that olfactory impairment may be observed in patients with AD, PD, MCI, or other types of dementia. Even though smell tests are able to detect olfactory loss caused by neurodegenerative diseases, they cannot reliably distinguish between certain diseases.</br> <br><b>Conclusions:</b> In individuals with cognitive impairment or neurodegenerative diseases, olfactory assessment has repeatedly been reported to be used for early diagnosis, but not for differential diagnosis.</br>.
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Affiliation(s)
- Martina Kovalová
- Center for Research and Science, Faculty of Health Sciences, Palacký University Olomouc, Czech Republic
| | - Nikol Gottfriedová
- Department of Epidemiology and Public Health, Faculty of Medicine, University of Ostrava, Czech Republic
| | - Eva Mrázková
- Center for Research and Science, Faculty of Health Sciences, Palacký University Olomouc, Czech Republic
| | - Vladimír Janout
- Center for Research and Science, Faculty of Health Sciences, Palacký University Olomouc, Czech Republic
| | - Jana Janoutová
- Center for Research and Science, Faculty of Health Sciences, Palacký University Olomouc, Czech Republic
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Liu D, Lu J, Wei L, Yao M, Yang H, Lv P, Wang H, Zhu Y, Zhu Z, Zhang X, Chen J, Yang QX, Zhang B. Olfactory deficit: a potential functional marker across the Alzheimer's disease continuum. Front Neurosci 2024; 18:1309482. [PMID: 38435057 PMCID: PMC10907997 DOI: 10.3389/fnins.2024.1309482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Accepted: 02/02/2024] [Indexed: 03/05/2024] Open
Abstract
Alzheimer's disease (AD) is a prevalent form of dementia that affects an estimated 32 million individuals globally. Identifying early indicators is vital for screening at-risk populations and implementing timely interventions. At present, there is an urgent need for early and sensitive biomarkers to screen individuals at risk of AD. Among all sensory biomarkers, olfaction is currently one of the most promising indicators for AD. Olfactory dysfunction signifies a decline in the ability to detect, identify, or remember odors. Within the spectrum of AD, impairment in olfactory identification precedes detectable cognitive impairments, including mild cognitive impairment (MCI) and even the stage of subjective cognitive decline (SCD), by several years. Olfactory impairment is closely linked to the clinical symptoms and neuropathological biomarkers of AD, accompanied by significant structural and functional abnormalities in the brain. Olfactory behavior examination can subjectively evaluate the abilities of olfactory identification, threshold, and discrimination. Olfactory functional magnetic resonance imaging (fMRI) can provide a relatively objective assessment of olfactory capabilities, with the potential to become a promising tool for exploring the neural mechanisms of olfactory damage in AD. Here, we provide a timely review of recent literature on the characteristics, neuropathology, and examination of olfactory dysfunction in the AD continuum. We focus on the early changes in olfactory indicators detected by behavioral and fMRI assessments and discuss the potential of these techniques in MCI and preclinical AD. Despite the challenges and limitations of existing research, olfactory dysfunction has demonstrated its value in assessing neurodegenerative diseases and may serve as an early indicator of AD in the future.
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Affiliation(s)
- Dongming Liu
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Jiaming Lu
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Liangpeng Wei
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Mei Yao
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Huiquan Yang
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Pin Lv
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Haoyao Wang
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Yajing Zhu
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
| | - Zhengyang Zhu
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
| | - Xin Zhang
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Jiu Chen
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
| | - Qing X. Yang
- Department of Radiology, Center for NMR Research, Penn State University College of Medicine, Hershey, PA, United States
| | - Bing Zhang
- Department of Radiology, Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University, Nanjing, China
- Institute of Medical Imaging and Artificial Intelligence, Nanjing University, Nanjing, China
- Medical Imaging Center, The Affiliated Drum Tower Hospital, Medical School of Nanjing University, Nanjing, China
- State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing, China
- Jiangsu Key Laboratory of Molecular Medicine, Nanjing, China
- Institute of Brain Science, Nanjing University, Nanjing, China
- Jiangsu Provincial Medical Key Discipline (Laboratory), Nanjing, China
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Zhou C, Yang C, Ai Y, Fang X, Zhang A, Wang Y, Hu H. Valid olfactory impairment tests can help identify mild cognitive impairment: an updated meta-analysis. Front Aging Neurosci 2024; 16:1349196. [PMID: 38419646 PMCID: PMC10900519 DOI: 10.3389/fnagi.2024.1349196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Accepted: 01/29/2024] [Indexed: 03/02/2024] Open
Abstract
Background Olfactory testing is emerging as a potentially effective screening method for identifying mild cognitive impairment in the elderly population. Objective Olfactory impairment is comorbid with mild cognitive impairment (MCI) in older adults but is not well-documented in subdomains of either olfactory or subtypes of cognitive impairments in older adults. This meta-analysis was aimed at synthesizing the differentiated relationships with updated studies. Methods A systematic search was conducted in seven databases from their availability to April 2023. A total of 38 publications were included, including 3,828 MCI patients and 8,160 healthy older adults. Two investigators independently performed the literature review, quality assessment, and data extraction. The meta-analyses were conducted with Stata to estimate the average effects and causes of the heterogeneity. Results Compared to normal adults, MCI patients had severe impairments in olfactory function and severe deficits in specific domains of odor identification and discrimination. Olfactory impairment was more severe in patients with amnestic mild cognitive impairment than in patients with non-amnestic MCI. Diverse test instruments of olfactory function caused large heterogeneity in effect sizes. Conclusion Valid olfactory tests can be complementary tools for accurate screening of MCI in older adults.
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Affiliation(s)
- Chunyi Zhou
- School of Nursing, Hubei University of Chinese Medicine, Wuhan, China
| | - Chongming Yang
- Research Support Center, College of Family, Home, and Social Sciences, Brigham Young University, Provo, UT, United States
| | - Yating Ai
- School of Nursing, Hubei University of Chinese Medicine, Wuhan, China
| | - Xueling Fang
- School of Nursing, Hubei University of Chinese Medicine, Wuhan, China
| | - Ailin Zhang
- School of Nursing, Hubei University of Chinese Medicine, Wuhan, China
| | - Yuncui Wang
- School of Nursing, Hubei University of Chinese Medicine, Wuhan, China
- Engineering Research Center of TCM Protection Technology and New Product Development for the Elderly Brain Health, Ministry of Education, Wuhan, China
- Hubei Shizhen Laboratory, Wuhan, China
| | - Hui Hu
- School of Nursing, Hubei University of Chinese Medicine, Wuhan, China
- Engineering Research Center of TCM Protection Technology and New Product Development for the Elderly Brain Health, Ministry of Education, Wuhan, China
- Hubei Shizhen Laboratory, Wuhan, China
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Chen H, Ding Y, Huang L, Zhong W, Lin X, Zhang B, Zheng Y, Xu X, Lou M, Yuan C. The Association of Allergy-Related and Non-Allergy-Related Olfactory Impairment with Cognitive Function in Older Adults: Two Cross- Sectional Studies. Curr Alzheimer Res 2024; 20:811-820. [PMID: 38409711 DOI: 10.2174/0115672050284179240215052257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 01/23/2024] [Accepted: 01/24/2024] [Indexed: 02/28/2024]
Abstract
BACKGROUND Evidence on the association of Olfactory Impairment (OI) with age-related cognitive decline is inconclusive, and the potential influence of allergy remains unclear. OBJECTIVE We aimed to evaluate the cross-sectional associations of allergy-related and non-allergy- related OI to cognitive function. METHODS We included 2,499 participants from the Health and Retirement Study (HRS)-Harmonized Cognitive Assessment Protocol (HCAP) sub-study and 1,086 participants from the English Longitudinal Study of Ageing (ELSA)-HCAP. The Olfactory Function Field Exam (OFFE) using Sniffin' Stick odor pens was used to objectively assess olfactory function and an olfactory score <6/11 indicated OI. Mini-Mental Status Examination (MMSE) was used to assess global cognitive function and define cognitive impairment (<24/30). A neuropsychologic battery was used to assess five cognitive domains. RESULTS Compared to non-OI participants, individuals with OI had lower MMSE z-score [βHRS = -0.33, 95% Confidence Interval (CI): -0.41 to -0.24; βELSA = -0.31, -0.43 to -0.18] and higher prevalence of cognitive impairment (Prevalence Ratio (PR)HRS = 1.46, 1.06 to 2.01; PRELSA = 1.63, 1.26 to 2.11). The associations were stronger for non-allergy-related OI (βHRS = -0.36; βELSA = -0.34) than for allergy-related OI (βHRS = -0.26; βELSA = 0.13). Similar associations were observed with domain- specific cognitive function measures. CONCLUSION OI, particularly non-allergy-related OI, was related to poorer cognitive function in older adults. Although the current cross-sectional study is subject to several limitations, such as reverse causality and residual confounding, the findings will provide insights into the OI-cognition association and enlighten future attention to non-allergy-related OI for the prevention of potential cognitive impairment.
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Affiliation(s)
- Hui Chen
- School of Public Health, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Yihong Ding
- School of Public Health, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Liyan Huang
- School of Public Health, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Wansi Zhong
- Department of Neurology, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Xiaojun Lin
- School of Public Health, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Baoyue Zhang
- School of Public Health, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Yan Zheng
- Human Phenome Institute, School of Life Sciences, Fudan University, Shanghai, China
| | - Xin Xu
- School of Public Health, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Min Lou
- Department of Neurology, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Changzheng Yuan
- School of Public Health, the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
- Department of Nutrition, Harvard T.H. Chan School of Public Health, Boston, MA, USA
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Du S, Wang Y, Li G, Wei H, Yan H, Li X, Wu Y, Zhu J, Wang Y, Cai Z, Wang N. Olfactory functional covariance connectivity in Parkinson's disease: Evidence from a Chinese population. Front Aging Neurosci 2023; 14:1071520. [PMID: 36688163 PMCID: PMC9846552 DOI: 10.3389/fnagi.2022.1071520] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Accepted: 12/12/2022] [Indexed: 01/05/2023] Open
Abstract
Introduction Central anosmia is a potential marker of the prodrome and progression of Parkinson's disease (PD). Resting-state functional magnetic resonance imaging studies have shown that olfactory dysfunction is related to abnormal changes in central olfactory-related structures in patients with early PD. Methods This study, which was conducted at Guanyun People's Hospital, analyzed the resting-state functional magnetic resonance data using the functional covariance connection strength method to decode the functional connectivity between the white-gray matter in a Chinese population comprising 14 patients with PD and 13 controls. Results The following correlations were observed in patients with PD: specific gray matter areas related to smell (i.e., the brainstem, right cerebellum, right temporal fusiform cortex, bilateral superior temporal gyrus, right Insula, left frontal pole and right superior parietal lobule) had abnormal connections with white matter fiber bundles (i.e., the left posterior thalamic radiation, bilateral posterior corona radiata, bilateral superior corona radiata and right superior longitudinal fasciculus); the connection between the brainstem [region of interest (ROI) 1] and right cerebellum (ROI2) showed a strong correlation. Right posterior corona radiation (ROI11) showed a strong correlation with part 2 of the Unified Parkinson's Disease Rating Scale, and right superior longitudinal fasciculus (ROI14) showed a strong correlation with parts 1, 2, and 3 of the Unified Parkinson's Disease Rating Scale and Hoehn and Yahr Scale. Discussion The characteristics of olfactory-related brain networks can be potentially used as neuroimaging biomarkers for characterizing PD states. In the future, dynamic testing of olfactory function may help improve the accuracy and specificity of olfactory dysfunction in the diagnosis of neurodegenerative diseases.
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Affiliation(s)
- Shouyun Du
- Department of Neurology, Guanyun County People's Hospital, Lianyungang, China
| | - Yiqing Wang
- Department of Neurology, The Affiliated Suzhou Hospital of Nanjing University Medical School, Suzhou, China,Department of Neurology, Suzhou Science & Technology Town Hospital, Gusu School, Nanjing Medical University, Suzhou, China
| | - Guodong Li
- Department of Neurology, Guanyun County People's Hospital, Lianyungang, China
| | - Hongyu Wei
- Department of Neurology, The Affiliated Suzhou Hospital of Nanjing University Medical School, Suzhou, China
| | - Hongjie Yan
- Department of Neurology, Affiliated Lianyungang Hospital of Xuzhou Medical University, Lianyungang, China
| | - Xiaojing Li
- Department of Neurology, The Affiliated Suzhou Hospital of Nanjing University Medical School, Suzhou, China
| | - Yijie Wu
- Department of Neurology, The Affiliated Suzhou Hospital of Nanjing University Medical School, Suzhou, China
| | - Jianbing Zhu
- Department of Radiology, The Affiliated Suzhou Hospital of Nanjing University Medical School, Suzhou, China
| | - Yi Wang
- Department of Radiology, The Affiliated Suzhou Hospital of Nanjing University Medical School, Suzhou, China
| | - Zenglin Cai
- Department of Neurology, The Affiliated Suzhou Hospital of Nanjing University Medical School, Suzhou, China,Department of Neurology, Suzhou Science & Technology Town Hospital, Gusu School, Nanjing Medical University, Suzhou, China,*Correspondence: Zenglin Cai, ✉
| | - Nizhuan Wang
- School of Biomedical Engineering, ShanghaiTech University, Shanghai, China,Nizhuan Wang, ✉
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Yap AC, Mahendran R, Kua EH, Zhou W, Wang DY. Olfactory dysfunction is associated with mild cognitive impairment in community-dwelling older adults. Front Aging Neurosci 2022; 14:930686. [PMID: 36004001 PMCID: PMC9393534 DOI: 10.3389/fnagi.2022.930686] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 07/18/2022] [Indexed: 12/02/2022] Open
Abstract
Background Olfactory impairment is aging related and is associated with cognitive decline in older adults. However, it remains unclear if an olfactory impairment is associated with mild cognitive impairment (MCI) and the degree of impairment in the MCI subtypes. Materials and methods In a cohort of community-living older adults aged 60 years and above, 670 participants were recruited from the Community Health and Intergenerational (CHI) Study. Olfactory function was assessed using a locally developed nine-item smell test in association with neurocognitive assessments. Analysis of covariance (ANCOVA) was used to examine the association of smell identification score and clinical cognitive status while considering demographic, clinical, and neuropsychological factors with Bonferroni correction for group comparisons. Results Age-related smell detection between normal aging (NA) and MCI participants had no significant difference. The overall mean smell identification score in older adults was negatively correlated with age. The mean smell identification score of MCI participants was also not significantly different as compared with NA, but an amnestic MCI multiple domain (aMCI_MD) subgroup had significantly lower (impaired) mean smell identification scores compared with the NA and MCI single domain (amnestic and non-amnestic) group. Conclusion This study demonstrated that olfactory identification impairment is a comorbidity in older adults with amnestic MCI (aMCI) and is a potential marker associated with an early stage of a neurocognitive disorder. The smell test could act as a screening tool to help in the early detection of smell impairment for heterogeneous syndromes of MCI among community-dwelling older adults. Clinicians and researchers could benefit from utilizing the locally developed smell test to screen their patients or research participants before the initiation of an appropriate health intervention or in a clinical trial.
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Affiliation(s)
- Ai Che Yap
- Department of Food Science and Technology, National University of Singapore, Singapore, Singapore
| | - Rathi Mahendran
- Department of Psychological Medicine, Mind Science Centre, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Ee Heok Kua
- Department of Psychological Medicine, Mind Science Centre, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- Department of Psychological Medicine, National University Hospital, Singapore, Singapore
- *Correspondence: Ee Heok Kua,
| | - Weibiao Zhou
- Department of Food Science and Technology, National University of Singapore, Singapore, Singapore
- Weibiao Zhou,
| | - De Yun Wang
- Department of Otolaryngology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- De Yun Wang,
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