Long-Term Test-Retest Reliability of the UPSIT in Cognitively Intact Older Adults

Cognitive impairment, neurodegenerative disorders, and olfactory impairment: A literature review

<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>.

Vitamin D levels and olfactory dysfunction in multiple sclerosis patients

OBJECTIVE

The objective was to explore the possible relationship between the serum vitamin D level and olfactory impairment in a population of multiple sclerosis (MS) patients in Guizhou, China.

METHODS

We included 25 patients with MS and 18 healthy controls (HCs) who were recruited from the Affiliated Hospital of Guizhou Medical University from February 2021 to September 2021. The University of Pennsylvania Smell Identification Test (UPSIT) was used to test the patients' sense of smell, and the level of serum 25-hydroxyethylene polyprotein D was measured.

RESULTS

Serum vitamin D levels and UPSIT scores were significantly different between the MS group and the control group (both p < 0.001). Moreover, a significant positive correlation emerged between vitamin D levels and UPSIT scores in MS patients (r = 0.537, p = 0.021).

CONCLUSIONS

The serum vitamin D level may be involved in the regulation of olfactory dysfunction in MS patients in Guizhou, China.

"Mmm, Smells like Coffee!": How a Brief Odor Identification Test Could Help to Identify People with Mild Cognitive Impairment and Dementia

(1) Background: Dementia and mild cognitive impairment (MCI) are still underdiagnosed in the general population. Impaired odor identification has been identified as an early marker of MCI and dementia. We aimed to compare the additional diagnostic value of two odor identification tests to a cognitive screening test in detecting MCI or dementia. (2) Methods: The Sniffin' Sticks odor identification test (SS-OIT), a brief odor identification test (B-OIT) requiring the identification of coffee scent, and the Mini-Mental State Exam (MMSE) were administered to a consecutive series of 174 patients (93 with dementia, 42 with mild cognitive impairment, and 39 without cognitive impairment) referred for neuropsychological testing. (3) Results: Both participants with dementia and with MCI exhibited impairments in odor identification. The SS-OIT and the B-OIT were substantially correlated. Complementing MMSE scores with the SS-OIT or the B-OIT similarly improved the diagnostic accuracy of individuals with dementia and MCI. (4) Conclusions: People with suspected dementia or MCI may already benefit from brief odor identification tests. Although these tests require little additional time, they can notably increase sensitivity for dementia or MCI.

Local Brain Network Alterations and Olfactory Impairment in Alzheimer's Disease: An fMRI and Graph-Based Study

Alzheimer's disease (AD) is associated with the abnormal connection of functional networks. Olfactory impairment occurs in early AD; therefore, exploring alterations in olfactory-related regions is useful for early AD diagnosis. We combined the graph theory of local brain network topology with olfactory performance to analyze the differences in AD brain network characteristics. A total of 23 patients with AD and 18 normal controls were recruited for resting-state functional magnetic resonance imaging (fMRI), clinical neuropsychological examinations and the University of Pennsylvania Smell Identification Test (UPSIT). Between-group differences in the topological properties of the local network were compared. Pearson correlations were explored based on differential brain regions and olfactory performance. Statistical analysis revealed a correlation of the degree of cognitive impairment with olfactory recognition function. Local node topological properties were significantly altered in many local brain regions in the AD group. The nodal clustering coefficients of the bilateral temporal pole: middle temporal gyrus (TPOmid), degree centrality of the left insula (INS.L), degree centrality of the right middle temporal gyrus (MTG.R), and betweenness centrality of the left middle temporal gyrus (MTG.L) were related to olfactory performance. Alterations in local topological properties combined with the olfactory impairment can allow early identification of abnormal olfactory-related regions, facilitating early AD screening.

Olfaction and declarative memory in aging: a meta-analysis

Olfactory and declarative memory performances are associated, as both functions are processed by overlapping medial-temporal and prefrontal structures and decline in older adults. While a decline in olfactory identification may be related to a decline in declarative memory, the relationship between olfactory detection threshold and declarative memory remains unclear. In this meta-analysis, we assessed (i) the relationship between olfactory identification/detection threshold and verbal declarative memory in cognitively normal older adults, and (ii) the effect of age on these relationships. We included articles from PsychNet, PubMed, and Academic Search Complete according to the following criteria: (i) inclusion of cognitively normal older adults; (ii) assessment of episodic or semantic memory; and (iii) assessment of olfactory identification or detection threshold. Seventeen studies and 22 effect sizes were eligible and included in this meta-analysis. Olfactory identification was associated with episodic (small effect size: r = 0.19; k = 22) and semantic memory (small effect size: r = 0.16; k = 23). Similarly, the olfactory detection threshold was associated with both episodic (small to medium effect size: r = 0.25; k = 5) and semantic memory (small effect size: r = 0.17; k = 7). Age was found to moderate the relationship between olfactory detection threshold and memory performance. Both olfactory identification and detection threshold performances are associated with declarative memory in older adults, and age only moderates the relationship between olfactory detection threshold and declarative memory performances.

Computerized Games versus Crosswords Training in Mild Cognitive Impairment

BACKGROUND

Mild cognitive impairment (MCI) increases the risk of dementia. The efficacy of cognitive training in patients with MCI is unclear.

METHODS

In a two-site, single-blinded, 78-week trial, participants with MCI - stratified by age, severity (early/late MCI), and site - were randomly assigned to 12 weeks of intensive, home-based, computerized training with Web-based cognitive games or Web-based crossword puzzles, followed by six booster sessions. In mixed-model analyses, the primary outcome was change from baseline in the 11-item Alzheimer's Disease Assessment Scale-Cognitive (ADAS-Cog) score, a 70 point scale in which higher scores indicate greater cognitive impairment at 78 weeks, adjusted for baseline. Secondary outcomes included change from baseline in neuropsychological composite score, University of California San Diego Performance-Based Skills Assessment (functional outcome) score, and Functional Activities Questionnaire (functional outcome) score at 78 weeks, adjusted for baseline. Changes in hippocampal volume and cortical thickness on magnetic resonance imaging were assessed.

RESULTS

Among 107 participants (n=51 [games]; n=56 [crosswords]), ADAS-Cog score worsened slightly for games and improved for crosswords at week 78 (least squares [LS] means difference, -1.44; 95% confidence interval [CI], -2.83 to -0.06; P=0.04). From baseline to week 78, mean ADAS-Cog score worsened for games (9.53 to 9.93) and improved for crosswords (9.59 to 8.61). The late MCI subgroup showed similar results (LS means difference, -2.45; SE, 0.89; 95% CI, -4.21 to -0.70). Among secondary outcomes, the Functional Activities Questionnaire score worsened more with games than with crosswords at week 78 (LS means difference, -1.08; 95% CI, -1.97 to -0.18). Other secondary outcomes showed no differences. Decreases in hippocampal volume and cortical thickness were greater for games than for crosswords (LS means difference, 34.07; SE, 17.12; 95% CI, 0.51 to 67.63 [hippocampal volume]; LS means difference, 0.02; SE, 0.01; 95% CI, 0.00 to 0.04 [cortical thickness]).

CONCLUSIONS

Home-based computerized training with crosswords demonstrated superior efficacy to games for the primary outcome of baseline-adjusted change in ADAS-Cog score over 78 weeks. (Supported by the National Institutes of Health, National Institute on Aging; ClinicalTrials.gov number, NCT03205709.).

Odor identification predicts the transition of patients with isolated RBD: A retrospective study

Introduction

To determine if the severity of olfactory dysfunction in isolated REM sleep behavior disorder (IRBD) predicts conversion to Parkinson's disease (PD) or dementia with Lewy bodies (DLB).

Methods

Olfaction was tested using the Japanese version of the University of Pennsylvania Smell Identification Test (UPSIT‐J) in 155 consecutive patients with polysomnography‐confirmed IRBD and 34 healthy controls. IRBD patients were followed up for 5.8 ± 3.2 (range 0.2–11) years. Thirty‐eight patients underwent repeat UPSIT‐J evaluation at 2.7 ± 1.3 years after the baseline test.

Results

UPSIT‐J score was lower in IRBD patients than in age‐ and sex‐matched controls. The receiver operating characteristic curve analysis showed that the optimal cutoff score of 22.5 in UPSIT‐J discriminated between IRBD patients and controls with a sensitivity of 94.3% and specificity of 81.8%. Anosmia (UPSIT‐J score < 19) was present in 54.2% of IRBD patients. In total, 42 patients developed a neurodegenerative disease, of whom 17 had PD, 22 DLB, and 3 MSA. Kaplan–Meier analysis showed that the short‐term risk of Lewy body disease (LBD) was higher in patients with anosmia than in those without anosmia. At baseline, the UPSIT‐J score was similar between patients who developed PD and DLB (p = 0.136). All three IRBD patients (100%) who developed MSA did not have anosmia.

Conclusions

In IRBD patients, anosmia predicts a higher short‐term risk of transition to LBD but cannot distinguish between PD and DLB. At baseline, preserved odor identification may occur in latent MSA. Future IRBD neuroprotective trials should evaluate anosmia as a marker of prodromal LBD.

Odor identification impairment and cholinesterase inhibitor treatment in Alzheimer's disease

INTRODUCTION

This study evaluated acute change in odor identification following atropine nasal spray challenge, and 8-week change in odor identification ability, as a predictor of long-term improvement in patients with mild to moderate Alzheimer's disease (AD) who received open-label cholinesterase inhibitor treatment.

METHODS

In patients with clinical AD, the University of Pennsylvania Smell identification Test (UPSIT) was administered before and after an anticholinergic atropine nasal spray challenge. Patients were then treated with donepezil for 52 weeks.

RESULTS

In 21 study participants, acute atropine-induced decrease in UPSIT was not associated with change in the Alzheimer's Disease Assessment Scale - Cognitive Subscale (ADAS-Cog) or Selective Reminding Test (SRT). Decline in odor identification performance from baseline to week 8 was indicative of a future decline in cognitive performance over 52 weeks.

DISCUSSION

Change in odor identification with atropine challenge is not a useful predictor of treatment response to cholinesterase inhibitors. Short-term change in odor identification performance needs further investigation as a potential predictor of cognitive improvement with cholinesterase inhibitor treatment.

Development of Chinese odor identification test

Background

Olfactory dysfunction significantly reduces quality of life, with a prevalence as high as 20% in the general adult population. Odor identification (OI) tests are culturally dependent and widely used in clinical and epidemiological evaluations of olfaction. We aimed to develop a Chinese odor identification test (COIT) based on the Sniffin’ Sticks identification test.

Methods

Patients (n=60) with olfactory disorders and healthy controls (n=404) were recruited in the Smell and Taste Center of a tertiary-care university hospital. Unfamiliar odors in the Sniffin’ Sticks identification test were replaced to create a 16-item COIT, which was validated with a simplified Chinese version of the Cross-culture Smell Identification Test (CC-SIT) and Sniffin’ Sticks. A test-retest reliability of COIT was also conducted.

Results

Six odors with a correct recognition rate <75% were replaced with familiar odors for Chinese. The COIT score significantly correlated with both Sniffin’ Sticks (r=0.755 P<0.0001) and CC-SIT score (r=0.7462 P<0.0001). Based on the testing results of an additional 120 subjects, we concluded that scores of 12–16, 7–11, and 0–6 corresponded to normosmia, hyposmia, and anosmia, respectively. The 3-month test-retest-reliability coefficient was as high as 0.83.

Conclusions

The COIT is an effective tool for assessing olfactory function in the Chinese population.

The Human Brain Representation of Odor Identification in Amnestic Mild Cognitive Impairment and Alzheimer's Dementia of Mild Degree

Background: Odor identification (OI) ability is a suggested early biomarker of Alzheimer's disease. In this study, we investigated brain activity within the brain's olfactory network associated with OI in patients with amnestic mild cognitive impairment (aMCI) and mild Alzheimer's dementia (mAD) to uncover the neuronal basis of this impairment. Materials and Methods: Patients with aMCI (n = 11) or mAD (n = 6) and 28 healthy older adults underwent OI functional MRI (fMRI) at 3T, OI, odor discrimination, and cognitive tests and apolipoprotein-e4 (APOE4) genotyping. Eleven patients had cerebrospinal fluid (CSF) analyzed. Those with aMCI were followed for 2 years to examine conversion to dementia. Results: The aMCI/mAD group performed significantly worse on all OI tests and the odor discrimination test compared to controls. The aMCI/mAD group had reduced activation in the right anterior piriform cortex compared to the controls during OI fMRI [Gaussian random field (GRF) corrected cluster threshold, p < 0.05]. This group difference remained after correcting for age, sex education, and brain parenchymal fraction. This difference in piriform activity was driven primarily by differences in odor discrimination ability and to a lesser extent by OI ability. There was no group by odor discrimination/identification score interaction on brain activity. Across both groups, only odor discrimination score was significantly associated with brain activity located to the right piriform cortex. Brain activity during OI was not associated with Mini Mental Status Examination scores. At the group level, the aMCI/mAD group activated only the anterior insula, while the control group had significant activation within all regions of the olfactory network during OI fMRI. There was no association between brain activity during OI fMRI and total beta-amyloid levels in the CSF in the aMCI/mAD group. Conclusion: The OI impairment in aMCI/mAD patients is associated with significantly reduced activity in the piriform cortex compared to controls. Activation of downstream regions within the olfactory network is also significantly affected in the aMCI/mAD group, except the anterior insula, which is impinged late in the course of Alzheimer's disease. OI tests thus reflect Alzheimer's disease pathology in olfactory brain structures.

Olfactory loss and aging: connections with health and well-being

Age-related olfactory dysfunction, or presbyosmia, is a common sensory impairment in aging adults. People in this demographic group with comorbid conditions or exposure to viral, traumatic, or environmental insults remain at the greatest risk for impairment. Several methods for assessing olfaction exist, but they are only available in special settings and require consideration of age, sex, ancestry, and cognition. Perhaps most importantly, olfactory dysfunction has been suggested as an early sign of Alzheimer's and Parkinson's disease and therefore may serve as a tool in the diagnosis and prognosis of these neurodegenerative conditions. Outside of this context, olfactory loss also impacts nutrition, safety, and social relationships, and even predicts mortality itself. This review covers the detection and manifestations of olfactory decline in aging individuals and the myriad ways in which olfactory impairment is connected to their health and well-being.