Olfactory Identification in Subjective Cognitive Decline: A Meta-Analysis

Jobin, Benoît; Zahal, Rayane; Bussières, Ève-Line; Frasnelli, Johannes; Boller, Benjamin

doi:10.3233/jad-201022

Cited by 22 publications

(25 citation statements)

References 54 publications

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“…evaluating OF in individuals with subjective cognitive decline and in healthy older adults found that there was a significant difference, with slight relative impairment in patients with subjective cognitive decline. 668 In the Mayo Clinic Study of Aging, participants were classified as having normal cognition, amnestic MCI, nonamnestic MCI, or dementia. This population-based prospective cohort study found that olfactory impairment is associated with amnestic MCI and the progression of amnestic MCI to AD dementia.…”

Section: J Related To Neurodegenerative Diseasementioning

confidence: 99%

International consensus statement on allergy and rhinology: Olfaction

Patel

Holbrook

Turner

et al. 2022

Int Forum Allergy Rhinol

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Background:The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we have gathered experts from around the world to produce this International Consensus on Allergy and Rhinology: Olfaction (ICAR:O). Methods: Using previously described methodology, specific topics were developed relating to olfaction. Each topic was assigned a literature review, evidence-based review, or evidence-based review with recommendations format as dictated by available evidence and scope within the ICAR:O document. Following iterative reviews of each topic, the ICAR:O document was integrated and reviewed by all authors for final consensus. Results:The ICAR:O document reviews nearly 100 separate topics within the realm of olfaction, including diagnosis, epidemiology, disease burden, diagnosis, testing, etiology, treatment, and associated pathologies. Conclusion:This critical review of the existing clinical olfaction literature provides much needed insight and clarity into the evaluation, diagnosis, and treatment of patients with olfactory dysfunction, while also clearly delineating gaps in our knowledge and evidence base that we should investigate further.

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Section: J Related To Neurodegenerative Diseasementioning

confidence: 99%

International consensus statement on allergy and rhinology: Olfaction

Patel

Holbrook

Turner

et al. 2022

Int Forum Allergy Rhinol

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“…A previous meta-analysis summarizing the structural changes implicated in olfactory processing showed that patients with AD and MCI had smaller OB volumes and a smaller POC when compared to controls and that these volumetric reductions could be measured as early as the MCI stage (Jobin et al, 2021a ). Even altered olfactory identification function has been detected in subjective cognitive decline (SCD), a stage that occurs before MCI (Jobin et al, 2021b ). A recent study provided evidence that the amygdala (a component of the POC) functions as a shared neural substrate linking olfactory identification ability with cognitive function (Shao et al, 2021 ; Tan et al, 2022 ).…”

Section: Discussionmentioning

confidence: 99%

Olfactory function changes and the predictive performance of the Chinese Smell Identification Test in patients with mild cognitive impairment and Alzheimer's disease

et al. 2023

Front. Aging Neurosci.

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ObjectivesOlfactory disorder is one of the sensory features that reflects a decline in cognitive function. However, olfactory changes and the discernibility of smell testing in the aging population have yet to be fully elucidated. Therefore, this study aimed to examine the effectiveness of the Chinese Smell Identification Test (CSIT) in distinguishing individuals with cognitive decline from those with normal aging and to determine whether the patients with MCI and AD show changes in their olfactory identification abilities.MethodsThis cross-sectional study included eligible participants aged over 50 years between October 2019 and December 2021. The participants were divided into three groups: individuals with mild cognitive impairment (MCI), individuals with Alzheimer's disease (AD), and cognitively normal controls (NCs). All participants were assessed using neuropsychiatric scales, the Activity of Daily Living scale, and the 16-odor cognitive state test (CSIT) test. The test scores and the severity of olfactory impairment were also recorded for each participant.ResultsIn total, 366 eligible participants were recruited, including 188 participants with MCI, 42 patients with AD, and 136 NCs. Patients with MCI achieved a mean CSIT score of 13.06 ± 2.05, while patients with AD achieved a mean score of 11.38 ± 3.25. These scores were significantly lower than those of the NC group (14.6 ± 1.57; P < 0.001). An analysis showed that 19.9% of NCs exhibited mild olfactory impairment, while 52.7% of patients with MCI and 69% of patients with AD exhibited mild to severe olfactory impairment. The CSIT score was positively correlated with the MoCA and MMSE scores. The CIST score and the severity of olfactory impairment were identified as robust indicators for MCI and AD, even after adjusting for age, gender, and level of education. Age and educational level were identified as two important confounding factors that influence cognitive function. However, no significant interactive effects were observed between these confounders and CIST scores in determining the risk of MCI. The area under the ROC curve (AUC) generated from the ROC analysis was 0.738 and 0.813 in distinguishing patients with MCI and patients with AD from NCs based on the CIST scores, respectively. The optimal cutoff for distinguishing MCI from NCs was 13, and for distinguishing AD from NCs was 11. The AUC for distinguishing AD from MCI was 0.62.ConclusionsThe olfactory identification function is frequently affected in patients with MCI and patients with AD. CSIT is a beneficial tool for the early screening of cognitive impairment among elderly patients with cognitive or memory issues.

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“…SCD has been linked to slightly impaired odor identification abilities, according to a recent meta-analysis ( Jobin, Zahal, et al, 2021 ). Although the participants who reported exclusively SCD did not show olfactory decline in our sample, the small group of individuals that reported SCD + SOI showed worse objective olfactory performance compared to both control and SCD groups.…”

Section: Discussionmentioning

confidence: 99%

Subjective Impairments in Olfaction and Cognition Predict Dissociated Behavioral Outcomes

Cedrés

Aejmelaeus-Lindström

Ekström

et al. 2022

The Journals of Gerontology: Series B

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Background Self-rated subjective cognitive decline (SCD) and subjective olfactory impairment (SOI) are associated with objective cognitive decline and dementia. However, their relationship and co-occurrence is unknown. We aimed to (1) describe the occurrence of SOI, SCD and their overlap in the general population; (2) compare SOI and SCD in terms of longitudinal associations with corresponding objective olfactory and cognitive measures; and (3) describe how SOI and SCD may lead to distinct sensory and cognitive outcomes. Methods Cognitively unimpaired individuals from the third wave of the Swedish population-based Betula study (n = 784, aged 35-90 years; 51% females) were split into self-rated SOI, SCD, overlapping SCD+SOI, and controls. Between-subjects and within-subject repeated measures MANCOVA were used to compare the groups regarding odor identification, cognition, age, sex and education. Spearman correlation was used to assess the different patterns of association between olfaction and cognition across groups. Results SOI was present in 21.1% whereas SCD was present in 9.9% of participants. According to a chi-square analysis, the SCD+SOI overlap (2.7%) is on a level that could be expected if the phenomena were independent. Odor identification in SOI showed decline at the 10-year follow-up (n=284) and was positively associated with cognition. The SOI and SCD groups showed distinct cognitive-olfactory profiles at follow-up. Conclusions SOI occur independently of SCD in the population, and these risk factors are associated with different cognitive and olfactory outcomes. The biological causes underlying SOI and SCD, as well as the risk for future cognitive impairment, need further investigation.

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Olfactory Identification in Subjective Cognitive Decline: A Meta-Analysis

Cited by 22 publications

References 54 publications

International consensus statement on allergy and rhinology: Olfaction

International consensus statement on allergy and rhinology: Olfaction

Olfactory function changes and the predictive performance of the Chinese Smell Identification Test in patients with mild cognitive impairment and Alzheimer's disease

Subjective Impairments in Olfaction and Cognition Predict Dissociated Behavioral Outcomes

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