Utility of olfactory identification test for screening of cognitive dysfunction in community-dwelling older adults

Background There is a need for a large-scale screening test that can be used to detect dementia in older individuals at an early stage. Olfactory identification deficits have been shown to occur in the early stages of dementia, indicating their usefulness in screening tests. This study investigated the utility of an olfactory identification test as a screening test for mild cognitive dysfunction in community-dwelling older people. Methods The subjects were city-dwelling individuals aged over 65 years but under 85 years who had not been diagnosed with dementia or mild cognitive impairment. The Japanese version of the Mild Cognitive Impairment Screen was used to evaluate cognitive function. Based on the results, the subjects were divided into two groups: healthy group and cognitively impaired group. Olfactory identification abilities based on the Japanese version of the University of Pennsylvania Smell Identification Test were compared between the groups. Results There were 182 participants in total: 77 in the healthy group and 105 in the cognitively impaired group. The mean olfactory identification test score of the cognitively impaired group was significantly lower than that of the healthy group. The cognitive impairment test score was significantly correlated with the olfactory identification test score. Conclusions Cross-sectional olfactory identification deficits at baseline in community-dwelling older adults reflected cognitive dysfunction. Assessing olfactory identification ability might be useful as a screening test for mild cognitive dysfunction in community-dwelling older people.

Maturation of odour identification ability and related factors in children

Background: Olfaction plays an important role in our daily and social lives, both as adults and as children. This study assessed whether the ability to identify odours increases with age, as well as the ability in various age groups and the factors involved. Methods: The survey was performed in 2017 on 697 Japanese children (366 girls and 331 boys) aged 6–18 years who lived in Tsunan, Niigata Prefecture, Japan by using the ‘Open Essence’, a card-type odour identification test. We collected information regarding age, sex, and physical characteristic. We also inquired whether participants had siblings or if members of the family smoked, and whether they had conversations about odour at home. Statistical analysis was performed to evaluate the factors affecting odour identification abilities. Results: The results showed that the odour identification abilities of children increase with age, and children who have daily conversations about odours at home have better odour identification abilities. Conclusions: Odour identification ability increases with age. In addition, our findings suggest that conversation may positively affect odour identification. Hence, it is important for children to be exposed to an environment where they develop an interest in smells for better growth of their olfactory identification ability.

Serum C-Reactive Protein Is Negatively Associated With Olfactory Identification Ability in Older Adults

Importance Olfactory deficits are common in aging and associated with several conditions linked to inflammation. A few studies suggest that increased concentration of pro-inflammatory biomarkers may be related to olfactory deficits, but these associations are understudied in population-based samples. Objective To investigate the association between serum concentrations of C-reactive protein (CRP) and olfactory identification level as well as rate of change in aging. Methods We included 1,721 participants (mean age 70.5 years; 61.9% female) with at least two olfactory assessments across the 12-year follow-up. Baseline level and change in odor identification were estimated with linear mixed models as a function of CRP levels, derived from blood plasma at baseline. Results Results indicated a negative dose–response association between CRP level and odor identification scores at baseline, after adjustment for demographic, cognitive, health, and lifestyle factors. CRP levels ranging between 11 and 20 mg/L were significantly related to lower olfactory ability (β = −0.811, 95% confidence interval [CI] [−1.503 to −0.118]; p = .022). Likewise, CRP values above 20 mg/L were related to lower olfactory scores, an association that approached statistical significance (β = −0.996, 95% CI [−2.045 to 0.054]; p = .063). We found no associations between CRP and olfactory change ( ps > .368). Sensitivity analyses showed that associations between CRP and olfaction were confined to younger participants (age ≤72 years) and men ( ps < .034). Conclusions Our findings suggest a negative association between serum CRP levels and olfactory identification ability in aging that may be dependent on age and sex.

Olfactory Identification in Subjective Cognitive Decline: A Meta-Analysis

Background: Recently, subjective cognitive decline (SCD) has been considered to be one of the first signs of Alzheimer’s disease (AD). Since this potential early marker is sensitive but not specific to AD, combining it with other markers could ensure higher accuracy when predicting which persons with SCD will convert to AD. Since olfactory dysfunction is observable in both AD and mild cognitive impairment (MCI), it is a promising marker that could help improve the early diagnosis of AD. Objective: The aim of this meta-analysis was to verify whether the presence of SCD is associated with a decrease in olfactory identification ability. Methods: We collected articles from the following databases: PsychNet, PubMed, Ebsco, and ProQuest using the keywords: “SCD”, “subjective cognitive decline”, “subjective cognitive impairment”, “subjective memory impairment”, “subjective memory decline”, “cognitive complaints”, “memory complaints”, “cognitive concerns”, “memory concerns”, “olfac*” and “smell”. We included articles according to the following criteria: 1) participants aged 50 and over; 2) presence of an SCD group or a conceptual equivalent; 3) presence of a healthy control group with the same age range; and 4) assessment of olfactory identification ability. Results: Five studies met the inclusion criteria. Small and homogeneous effects were observed for olfactory identification alteration in individuals with SCD relative to controls (g = –0.16, 95% CI [–0.46, 0.14]). Conclusion: Despite the low number of studies included, the findings suggest that odor identification is slightly altered in SCD compared to healthy older adults. This alteration in individuals with SCD could be an early marker of AD.

Development of the Spanish Version of Sniffin’s Sticks Olfactory Identification Test: Normative Data and Validity of Parallel Measures

The Sniffin’ Sticks Olfactory Identification Test is a tool for measurement of olfactory performance developed in Germany and validated in several countries. This research aims to develop the Spanish version of the Sniffin’ Sticks Olfactory Identification Test and obtain normative values for the Spanish population. The parameters are free recall and subjective intensity of odorants are included. The influence of possible demographic covariates such as sex, age, smoking, or educational level are analyzed, and the items that best discriminate are studied. In addition, the internal structure validity of the blue and purple versions is studied as a parallel measure, and a cultural adaptation of the purple version is carried out. For this, three independent samples of normosmic healthy volunteers were studied. To obtain normative values, the sample was of 417 participants (18–89 years). For the internal structure validity study of both versions, the sample was 226 (18–70 years), and for familiarity of the purple version, the sample was 75 participants (21–79 years). Results indicated that men and women and smokers and non-smokers perform equally. However, differences were found as age progresses, being more pronounced after 60 years old in all three measurements of the identification test. This research also provides the items that best discriminate in the blue version and a cultural adaptation for the purple version. In conclusion, the Sniffin’ Sticks Odor Identification Test is a suitable tool for olfactory assessment in the Spanish population. The instrument has been expanded with two new scores, and normative data as a function of age are provided. Its parallel version also seems appropriate for testing, as items have been culturally adapted and evidence of internal structure validity for both versions is reported.

Acute systemic experimental inflammation does not reduce human odor identification performance

Olfactory dysfunction is a common symptom of various diseases but the underlying pathophysiology has not been fully understood. Evidence from both animal and human studies suggests that local inflammation of the olfactory epithelium is linked to olfactory dysfunction. However, whether systemic inflammation causes olfactory dysfunction is yet to be determined. In the present behavioral study, we set out to test whether acute systemic inflammation impairs olfactory identification performance by inducing a transient and controlled state of systemic inflammation using an experimental endotoxemia model. We treated young, otherwise healthy, participants (N=20) with a relatively high dose (2.0 ng/kg) of lipopolysaccharide (LPS) and a placebo treatment in a double-blind within-subject design, and assessed participants’ ability to identify odors using the MONEX-40, a reliable method for experimental assessment of odor ID ability in healthy and young individuals. Our results show that olfactory identification performance was not affected by the acute systemic inflammation triggered by the injection of LPS. Moreover, no associations were found between the change of olfactory performance followed by LPS injection and levels of circulating pro-inflammatory cytokines (interleukin-6, interleukin-8, and tumor necrosis factor-α). Because experimental LPS-induced systemic inflammation does not affect olfactory identification performance, our findings suggest that chronic, rather than transient, systemic inflammation is a more likely mechanism to explore in order to explain the olfactory deficits observed in inflammatory diseases.