TOM-32-An extended test for the assessment of olfactory memory

A novel olfactory sorting task

BACKGROUND

This study aimed to develop a simple self-administered screening tool for odor memory, which allowed users to self-test their olfactory function repeatedly even at home.

METHODS

One hundred and ten participants were recruited (30 men, age = 50.1 ± 9.9 years; 80 women, age = 47.1 ± 11.5 years); half of them were heathy volunteers, the other half were patients with olfactory dysfunction. Fifty-one healthy participants volunteered for a retest within an interval of a maximum of 14 days. Olfactory function was assessed using the extended Sniffin' Sticks test (SST) comprising tests for odor threshold, identification, and discrimination. All participants received the Novel Olfactory Sorting Task (NOST) which is based on the sorting of 12 matching pairs of odors involving olfactory and cognitive functions. After that, all participants rated questions related to their test performance and the practicability of the test.

RESULTS

Consistent with the previous literature, significant effects of age were found. Results showed an acceptable test-retest reliability and a satisfactory validity of the NOST. The NOST score not only had positive correlations with SST, but also was capable of differentiating severe hyposmia/anosmia from normosmia by the score of 5.5 (sensitivity of 76.2%, specificity of 77.6%).

CONCLUSION

The present study showed the good reliability, validity, and possible clinical usefulness of the NOST. As a self-performed screening test, it can be comprehended and conducted easily, which may provide a quick and simple approach to obtaining a global estimation of olfactory and cognitive functions.

Gender differences in the relationship between neuroticism and odor memory

Given the indications on the relationship between neuroticism and various olfactory functions as well as the emotionality of odor memory, it is surprising that no research so far has investigated whether neuroticism corresponds with odor memory performance. Thus, the purpose of our study was to address this question in the context of gender differences. Participants (73 men) completed the 60-items NEO Five Factor Inventory and participated in 32-items "Test for odor memory". In the separate analyses conducted for men and women, we demonstrated that women outperformed men regarding the number of correct odor recognitions in the odor memory test and had higher neuroticism level than men. Spearman correlation showed further that neuroticism was positively associated with D-prime (R = 0.3, p = .021) and the number of correct odor recognitions in women (R = 0.32, p = .014). This effect was, respectively, moderately (B10 = 5.2) and strongly confirmed using the Bayesian approach (B10 = 8). However, Bonferroni post-hoc correction for multiple comparisons further revealed that in case of neuroticism and the number of hits, as well as D-prime, alpha level was below significance, indicated by p = .006. The correlation between neuroticism level and odor memory performance was significantly higher in women compared to men (Z = 1.8, p = .038), while in case of neuroticism and D-prime, it was on a trend level (Z = 1.5, p = .074). Overall, the present results indicate that neuroticism might be linked to conscious odors' remembering for women, which can be explained by the warning role of odor memory and its connection to limbic structures, as well as by the higher level of neuroticism and odor memory performance in women compared to men.

Olfactory memory in mild cognitive impairment and Alzheimer's disease

Introduction

Olfaction is impaired in Alzheimer's disease (AD). However, olfactory memory has rarely been examined. As the pathogenesis of AD remains largely unknown, collecting more data regarding the occurrence and progression of its symptoms would help gain more insight into the disease.

Objective

To investigate olfactory memory and its relationship with verbal memory and other clinical features in patients with early-stage AD.

Methods

Three groups of participants were enrolled in this study: patients with mild dementia due to AD (MD-AD, N = 30), patients with mild cognitive impairment due to AD (MCI-AD, N = 30), and cognitively normal older participants (CN, N = 30). All participants underwent cognitive evaluation (Clinical Dementia Rating scale, Mini Mental State Examination, Alzheimer's Disease Assessment Scale-Cognitive Subscale, delayed verbal recall, and verbal fluency tests) and assessment of olfactory immediate and delayed recognition memory.

Results

Olfactory immediate and delayed recognition memory scores were significantly lower in the MD-AD group than in the MCI-AD and CN groups. The MCI-AD and CN groups did not differ significantly [in both cases, Kruskal-Wallis test, p < 0.05; post hoc analysis revealed significant differences between the MD-AD and MCI-AD groups and between the MD-AD and CN groups (p < 0.05), and no significant difference between the MCI-AD and CN groups (p > 0.05)]. Verbal immediate recall, delayed recall after 5 min, and delayed recall after 30 min scores were significantly worse in the MD-AD and MCI-AD groups than in the CN group. MD-AD and MCI-AD groups did not differ significantly [in all cases Kruskal-Wallis test, p < 0.05; post hoc analysis revealed significant differences between MD-AD and CN groups, and MCI-AD and CN groups (p < 0.05) and no significant difference between MD-AD and MCI-AD groups (p > 0.05)]. Duration of AD symptoms was a strong predictor of both immediate and delayed olfactory recognition memory scores.

Conclusion

Olfactory memory impairment was observed in patients with AD. The changes progress during the course of the disease. However, unlike verbal memory, olfactory memory is not significantly impaired in the prodromal stage of AD.

Development and validation of the Olfactory Memory Test Battery (OMTB) based on odors with high- and low-verbalizability

BACKGROUND

Odor memory is an important field of clinical research for its distinctive characteristics, which differ from those of other sensory systems. To date, several tests have been implemented for the assessment of odor memory. Despite a range of studies demonstrating the importance of verbal mediation in odor memory, few have distinguished odor memory performance in different odor verbalization levels.

NEW METHOD

We aimed to develop a standardized odor memory test toolbox with one group of odors that are easily verbally identified and the other group of odors that are difficult to identify. The test contained two odor categories (high- and low-verbalizability odors), each consisting of three subtests (short- and long-term memory and working memory).

RESULTS

Satisfactory test-retest reliability and solid validity of the odor recognition and working memory test were shown in both odor categories. Moreover, people scored significantly better with high- than low-verbalizability odors. A negative age effect on odor memory performance was also found.

COMPARISON WITH EXISTING METHODS

No previous odor memory test distinguished odor memory performance in different odor verbalization levels, while the Olfactory Memory Test Battery (OMTB) contains high- and low-verbalizability odors and each category has three subtests.

CONCLUSIONS

The present study indicated the OMTB is a comprehensive assessment of odor memory with good reliability and validity. All subtests can be used separately or in combination with each other according to the clinical and research needs.

Reduced Olfactory Memory Performance Is Associated with Executive Function Deficits in Older Adults

INTRODUCTION

Previous research has identified an association between olfactory impairment (reduced odor sensitivity/ identification/ discrimination) and cognitive impairment in older adults. The present study focused on the relationship between olfactory memory performance and cognitive/affective functioning.

METHOD

Recognition performance for olfactory and visual stimuli (control condition) was tested through a matching task in older adults (n = 44; M_age = 76 years) and younger adults (n = 56; M_age = 24 years). Additionally, negative affect (anxiety, depression) and cognitive functioning were assessed via validated questionnaires and a neuropsychological test battery.

RESULTS

The older participants performed worse than the younger adults in the olfactory memory task. In older adults, difficulties in remembering odors were associated with reduced odor identification and executive functioning (reduced cognitive flexibility). Affective well-being was not related to olfactory memory performance.

IMPLICATION

Olfactory memory impairment in older adulthood might be a marker for cognitive decline in areas related to executive functions.

International consensus statement on allergy and rhinology: Olfaction

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.

Clinical assessment of olfactory function

Approximately 5% of the general population is affected by functional anosmia with approximately additional 15% exhibiting decreased olfactory function. Many of these individuals ask for help. Because the subjective rating of olfactory function is biased, assessment of olfactory function is important. Olfactory measurements are needed for patient counseling and the tracking of changes in the sense of smell over time. The present review provides an overview of frequently used psychophysical tests for olfactory function, discusses differences between threshold and suprathreshold aspects of olfactory function, and gives examples on how to apply psychophysical tests.