Olfactory Identification Ability Research Articles

Relationship between olfactory and gustatory functions: The Iwaki health promotion project 2019

ObjectiveOlfactory and gustatory functions are important sensory aspects in humans. Although they are believed to influence each other, their interrelationship is not well understood. In this study, we aimed to investigate the relationship between the olfactory and gustatory functions based on the results of a large-scale epidemiological study (Iwaki Health Promotion Project) of the general local population. MethodsWe analyzed 565 participants who underwent taste and olfactory tests in the 2019 Iwaki Project. Gustatory function was tested for four taste qualities (sweet, sour, salty, and bitter) using whole-mouth taste tests. Olfactory function was tested using the University of Pennsylvania Smell Identification Test modified for Japanese (UPSIT-J). We evaluated sex-related differences between olfactory and gustatory functions and the effects of various factors on olfactory identification using multivariate analysis. Furthermore, we compared the percentage of accurate UPSIT-J responses between the normal and hypogeusia groups. We also analyzed the effects of taste and olfactory functions on eating. ResultsOlfactory and gustatory functions were lower in men than in women. Among the four taste qualities, salty taste was the most closely associated with olfactory identification ability, with lower olfactory scores of salty taste in the hypogeusia group than in the normal group. Moreover, the hyposmia group had higher daily salt intake than the normal olfaction group in women. ConclusionThese results suggest that olfactory identification tests may be useful in predicting elevated salt cognitive thresholds, leading to a reduction in salt intake, which may contribute to hypertension prevention.

Neuropsychiatric correlates of olfactory identification and traumatic brain injury in a sample of impulsive violent offenders.

Olfactory deficits have a diverse etiology and can be detected with simple olfactory tests. Key olfactory pathways are located within the frontal and temporal lobes where they are vulnerable to damage due to head trauma. Orbitofrontal cortex (OFC) integrity is important for olfaction and aspects of behavioral regulation. We measured olfactory identification ability in a sample of impulsive violent offenders to determine its associations with history of traumatic brain injury (TBI) and a range of neuropsychiatric indices, including proxies for cognitive ability, impulsivity and social connectedness. Male participants were drawn from the ReINVEST study, a randomized controlled trial of sertraline to reduce recidivism in violent impulsive offenders. Criteria for participation in the study included a minimum age of 18 years, a documented history of two or more violent offenses, and a score of 70 or above on the Barratt Impulsiveness Scale (BIS-11). The 16-item "Sniffin sticks" (SS) odor identification test (OI) was administered as were standardized questionnaires regarding previous TBI, additional measures to screen cognition [word reading test of the Wechsler Individuals Achievement Test (WIAT), social connectedness (the Duke Social Support Scale), and a range of other neuropsychiatric conditions or symptoms]. The sample SS scores were compared against published age-specific norms. Univariate and multivariate analyses were performed with SS score (linear regression, within those without hyposmia) or hyposmia (logistic regression) as the outcome. The mean OI scores were lower than population norms and 16% of participants were classified as hyposmic. Univariate analyses showed associations of SS score with age, WIAT score, impulsivity, TBI and TBI severity, social connectedness, childhood sexual abuse, suicidality and current use of heroin. In multivariate analyses, age, TBI severity and WIAT remained as significant independent predictors of SS score (within the normosmic range) or hyposmia (logistic regression). Olfactory performance was associated with multiple behavioral phenomena in a pattern that would be consistent with this serving as a proxy for orbitofrontal functioning. As such, OI testing may have utility in further studies of offenders. In future, we will examine whether olfactory score predicts recidivism or response to the administration of sertraline, in terms of reducing recidivism.

Association between olfactory function and cognitive impairment in dementia‐free older adults in Taiwan: A longitudinal cohort study

AbstractBackgroundThe olfactory impairment could be one of the earliest signs of cognitive impairment. However, limited studies have evaluated olfactory function and cognitive domains in Asian older adults. This study aimed to relate olfaction with global and domain‐specific cognition in Taiwan’s community‐dwelling, non‐demented older adults.MethodThis cohort study is part of the Taiwan Initiative for Geriatric Epidemiological Research, including 310 non‐demented older adults between 2015‐2019 with two repeated measures on cognitive function. Global and domain‐specific (memory, executive function, attention, and language) cognition were assessed by the Taiwanese version of Montreal Cognitive Assessment (MoCA‐T) and a battery of neuropsychological tests, respectively. The Sniffin' Sticks‐Odor Identification Test (SS‐OIT) was utilized to identify impaired olfaction. The generalized linear mixed model was used to examine the association of SS‐OIT with cognitive function over time, after adjustment for age, sex, years of education, apolipoprotein E ε4 status, presence of depression, sleep quality, chronic respiratory diseases, smoking, practice effect and follow‐up time. Subgroup analyses were also conducted.ResultBetter olfactory identification ability (i.e., increased SS‐OIT score) was associated with better performance of global cognition (MoCA‐T: β = 0.14, 95% confidence interval = 0.05‐0.24), memory (logical memory ‐ immediate and delayed theme and free recall: β = 0.06 to 0.09), executive function (trail making test‐A: β = 0.05 for baseline, ‐0.03 for interaction with follow‐up years), and verbal fluency (β = 0.08). Anosmia (SS‐OIT score ≦8) was associated with impaired memory [the lowest tertile (T1) vs. higher tertiles (T2+T3), adjusted odds ratio (aOR): 2.40 to 3.06], and verbal fluency (T1 vs. T2+T3, aOR = 2.39). After stratified analyses, the associations above remained significant in apolipoprotein E ε4 non‐carriers (MoCA‐T: β = 0.19; memory: β = 0.08 to 0.11; verbal fluency: β = 0.08), older adults without respiratory diseases (MoCA‐T: β = 0.14; memory: β = 0.06 to 0.10; verbal fluency: β = 0.10), and older adults without depression (MoCA‐T: β = 0.14; memory: β = 0.06 to 0.09; trail making test‐A: β = 0.04 for baseline, ‐0.02 for interaction with follow‐up years; verbal fluency: β = 0.09).ConclusionImpaired olfactory identification is associated with poor global or domain‐specific cognition in non‐demented older adults. Further research is required to validate our findings and clarify the underlying mechanism between anosmia and cognitive impairment.

Could olfactory identification be a prognostic factor in detecting cognitive impairment risk in the elderly?

Aging contributes to the deterioration of the olfactory system in humans. Several studies indicate that the olfactory identification test alone may function as a screening test for olfactory dysfunction and they are more feasible to apply in clinical practice. Olfactory identification may be a predictor for cognitive impairment. Multiple studies have considered the use of odor identification as a measure to identify the conversion from normality to mild cognitive impairment or dementia. The objectives were (i) to elucidate the associations between cognitive status and olfactory identification performance in aging; (ii) understand the predictive value of olfactory capacity in identifying subjects with cognitive impairment risk; and (iii) to study how cognitive status and olfactory identification relate with other variables of wellness in aging, such as functional capabilities and clinical measures. For this purpose, a group of 149 participants (77.15 ± 7.29 years; 73 women of 76.7 ± 8 years and 76 men of 77.6 ± 6.52 years) were recruited and were subjected to a sociodemographic questionnaire, a psychological screening tool of general cognitive status, an olfactory identification evaluation, and clinical measures. The participants were divided into groups based on their cutoff scores of previous scientific reports about the Spanish version of Montreal Cognitive Assessment. Our results indicate an age-associated decline in olfactory identification ability and intensity of odor perception. The predictive ability of olfactory identification scores for the risk of mild and severe impairment is around 80%. Olfactory identification decreases with cognitive function. Performance in odor identification is associated with impairment of episodic memory and executive functions. These findings further our current understanding of the association between cognition and olfaction, and support olfactory assessment in screening those at higher risk of dementia.

Olfactory dysfunction in Japanese children with moderate-to-severe allergic rhinitis

ObjectiveDetailed quantitative studies on olfaction remain inadequate in patients with paediatric allergic rhinitis (AR). This study examined olfactory dysfunction in children with AR. MethodsFrom July 2016 to November 2018, children aged 6–9 years were recruited and grouped as AR (n = 30) or without AR (control group, n = 10). Odour identification was evaluated by the Universal Sniff (U-Sniff) test and the Open Essence (OE). The results were compared between the AR and control groups. Intranasal mucosa findings, nasal smear eosinophil counts, blood eosinophil counts, total immunoglobulin E (IgE) levels, Japanese cedar-specific IgE and Dermatophagoides pteronyssinus-specific IgE were evaluated in all participants. Additionally, the presence of sinusitis and adenoid hypertrophy in patients with AR was also evaluated by sinus X-ray examinations. ResultsThe median U-Sniff test scores were not significantly different between the AR and control groups (9.0 vs. 10.0, respectively; p = 0.107). The OE score was significantly lower in the AR group than in the control group (4.0 vs. 8.0; p = 0.007, respectively), especially in the moderate-to-severe AR group versus the control group (4.0 vs. 8.0; p = 0.004). Furthermore, in the OE, the correct answer rates for ‘wood’, ‘cooking gas’ and ‘sweaty socks’ were significantly lower in the AR group than in the control group. ConclusionsPaediatric AR patients can reduce olfactory identification ability, and the degree may be associated with the severity of AR in nasal mucosal findings. Furthermore, olfactory dysfunction may slow down the response to ‘emergency situations’, such as gas leak.

Olfactory identification ability among schizophrenia patients, their first-degree relatives and healthy subjects.

Olfactory impairments, including identification, have been reported in patients with schizophrenia, while few studies have examined the olfactory function of unaffected first-degree relatives of patients with schizophrenia, and the sample sizes of first-degree relatives were relatively small. Here, we investigated olfactory identification ability among patients with schizophrenia, first-degree relatives and healthy controls (HCs) using relatively large sample sizes at a single institute. To assess olfactory identification ability, the open essence odorant identification test was administered to 172 schizophrenia patients, 75 first-degree relatives and 158 healthy controls. Differences in olfactory identification and correlations between olfactory ability and clinical variables were examined among these participants. We found a significant difference in olfactory identification ability among the diagnostic groups (p = 7.65 × 10-16). Schizophrenia patients displayed lower olfactory identification ability than first-degree relatives (Cohen's d = -0.57, p = 3.13 × 10-6) and healthy controls (d = -1.00, p = 2.19 × 10-16). Furthermore, first-degree relatives had lower olfactory identification ability than healthy controls (d = -0.29, p = 0.039). Olfactory identification ability moderately and negatively correlated with the duration of illness (r = -0.41, p = 1.88 × 10-8) and negative symptoms (r = -0.28, p = 1.99 × 10-4) in schizophrenia patients, although the correlation with the duration of illness was affected by aging (r = -0.24). Our results demonstrated that schizophrenia patients have impaired olfactory identification ability compared with first-degree relatives and healthy controls, and the impaired olfactory identification ability of first-degree relatives was intermediate between those in schizophrenia patients and healthy controls. Olfactory identification ability was relatively independent of clinical variables. Therefore, olfactory identification ability might be an intermediate phenotype for schizophrenia.

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

Olfactory 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. This 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. In 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. The 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.

Normative data for the Vietnamese smell identification test

IntroductionThe 12-item Vietnamese smell identification test (VSIT) has been developed to evaluate the olfactory function of the Vietnamese population. This study aimed to investigate the normative value of the VSIT in different age groups and sexes. MethodsThis cross-sectional study was conducted at Ho Chi Minh University Medical Center, Vietnam. All participants were evaluated for odor identification ability using the VSIT.We included healthy participants aged 18 years or older with no history of olfactory disturbances. ResultsA total of 391 healthy volunteers were recruited with a mean age of 45.80 years (SD: 17.62; range: 18–86; female: 63.4 %). The tenth percentile of scores on the 0–12 VSIT scale was 8.3 in participants aged 18–29 years, 9.0 in 30–39 years, 8.0 in 40–49 years, 7.8 in 50–59 years, 7.9 in 60–69 years and 6.0 in over 70 years. Young adults (18–39 years old) had better olfactory identification ability than older adults (over 50 years), p < 0.001. There was a significant main effect of sex on VSIT score (p = 0.02), suggesting that females outperformed males. Sensitivity to 8 odors were negatively correlated with age: lemon, garlic, banana, coffee, mango, guava, apple and watermelon (p < 0.05 in all cases) whereas four odors were age-independent including orange, fish sauce, soy sauce, and fish. ConclusionNormative data provide guidance for assessing individual olfactory function. However, there were significant sex and age effects on olfactory identification scores on the VSIT. Therefore, future studies should be conducted to better adjust for those confounders mentioned above.

Impaired odor identification ability and olfactory hedonic capacity in children with elevated autistic traits

AbstractAtypical olfactory function in autism spectrum disorder has been documented in numerous studies, but little is known about its occurrence in individuals with autistic traits. The aim of the current study was to investigate odor identification ability and olfactory hedonic capacity in children with autistic traits. We recruited 415 children and measured their autistic traits by the Short Autism Spectrum Quotient. The Universal Sniff (U‐Sniff) test was used to measure odor identification ability and olfactory hedonic capacity. Olfactory hedonic capacity was also measured using the children's version of the Chemosensory Pleasure Scale (CPS‐C). Odor identification and olfactory hedonic capacity measured by CPS‐C were negatively correlated with autistic traits. Children with higher autistic traits exhibited poorer odor identification ability and olfactory trait hedonic capacity measured by CPS‐C but intact olfactory state hedonic capacity measured by odor pleasantness. These results pertaining to odor identification and olfactory hedonic capacity may be the endophenotypic markers for autism spectrum disorder.Practical ApplicationsOur study extends the knowledge on children with high autistic traits and provides a new perspective on olfactory identification ability and olfactory hedonic capacity in children with high autistic traits. In addition, our findings suggest olfactory testing may provide a new approach for detecting and understanding autism.

Association between cognitive function and olfactory identification ability in community-dwelling older individuals.

[Purpose] We investigated whether olfactory identification ability may be useful for early detection of cognitive decline. [Participants and Methods] The study included 55 community-dwelling older individuals without a history of mild cognitive impairment or dementia, who were capable of living independently. Cognitive function was evaluated using the Japanese versions of the Mini-Mental State Examination and the Montreal Cognitive Assessment tools. The olfactory identification ability was evaluated using the Odor Stick Identification Test for the Japanese. We also investigated the association between olfactory identification ability and cognitive function. [Results] Based on the Japanese version of the Mini-Mental State Examination, all participants were categorized into the noncognitive decline group, and based on the Japanese version of the Montreal Cognitive Assessment tool, 21 participants were categorized into the cognitive decline group. With regard to olfactory discrimination ability, we observed a significant difference between participants with and without cognitive decline based on the Japanese version of the Montreal Cognitive Assessment scores. Furthermore, we observed a significant positive correlation between the Japanese version of the the Montreal Cognitive Assessment scores and the Odor Stick Identification Test for the Japanese scores, although no significant correlation was observed between the Japanese version of the Mini-Mental State Examination and the Odor Stick Identification Test for the Japanese scores. [Conclusion] Olfactory identification ability may be useful to detect early-stage cognitive decline in community-dwelling older individuals.

Olfactory identification ability in patients with mild cognitive impairment and Alzheimer’s disease

[Purpose] To examine the olfactory identification abilities and specify the difficult-to-identify odors in community-dwelling individuals with mild cognitive impairment (MCI) and Alzheimer's disease (AD). [Participants and Methods] We included, 12 and 17 patients with MCI (MCI group) and AD (AD group), respectively, and 30 community-dwelling older adults with no history of MCI or a dementia diagnosis (control group). Scores on the Japanese odor stick identification test (OSIT-J), an olfactory identification ability test, were compared among the three groups with intergroup differences examined accordingly. Next, we performed intergroup comparisons of the ratios of correct responses for each odor, and the difficult-to-identify odors were examined. [Results] OSIT-J scores of the MCI and AD groups were significantly lower than those of the control group. There were no intergroup differences in the correct identification of pungent odors. No patients in the AD group could identify the odor of cooking gas. The ability to identify food-related odors was reduced in the MCI and AD groups. [Conclusion] Patients with MCI and AD had reduced olfactory identification abilities in comparison to community-dwelling older adults without cognitive decline. These findings suggest the importance of olfactory evaluation before providing patients with dementia with therapeutic interventions associated with olfactory stimuli.

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

BackgroundThere 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.MethodsThe 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.ResultsThere 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.ConclusionsCross-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.

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. The survey was performed in 2017 on 697 Japanese children (366 girls and 331 boys) aged 6â€"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. 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. 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.

Brain response to food odors is not associated with body mass index and obesity-related metabolic health measures

Smell perception plays a role in eating behavior and might be involved in the development of obesity. In fact, olfactory function is impaired in obesity and might depend on metabolic health factors. To date, the underlying neural mechanisms remain unclear. Here, we investigate neural processing of food-related odors in normal-weight, overweight and obese individuals. Fifty-three young and healthy participants (28.8 ± 4.4 years, 27 female; 24 normal-weight, 10 overweight, and 19 obese) were presented with high- (chocolate, potato chips) and low-caloric (orange, cucumber) food odors during a functional magnetic resonance imaging (fMRI). We also assessed olfactory identification ability, body mass index (BMI), body fat percentage, insulin resistance, and leptin levels. In brief, olfactory perception of food odors was linked to brain activity in the entorhinal and piriform cortex, and the insula, hippocampus, and amygdala. Insulin resistance was negatively related to olfactory identification. Additionally, perception of sweet versus savory odors was related to a higher brain activity in the right middle/superior frontal gyrus. Finally, we found no effect of obesity status, BMI, metabolic factors, or body fat percentage on neural responses to food odors. Overall, this suggests that food odor processing might depend on factors other than body weight status or associated markers of metabolic health.

Olfactory identification impairment in early-and late-onset obsessive-compulsive disorder.

Early-onset obsessive-compulsive disorder (EOCD) is a comparatively severe subtype of obsessive-compulsive disorder (OCD). Olfactory dysfunction is a common symptom of OCD, but all previous studies have focused on late-onset OCD (LOCD). The current study compared olfactory identification ability in EOCD patients and age-matched and sex-matched LOCD patients and healthy controls. Thirty patients with EOCD, 30 patients with LOCD and 30 healthy controls were included in the study. Olfactory function was measured using the University of Pennsylvania Smell Identification Test. The Logical Memory and Visual Reproduction components of the Revised Wechsler Memory Scale were used to evaluate verbal and visual memory. There were significant differences in olfactory identification ability between the three groups. EOCD patients were comparable to LOCD patients, while both patients' group showing worse olfactory identification ability than controls. Olfactory identification ability was not significantly correlated with verbal and visual memory or clinical symptoms in the EOCD group or the LOCD group. The results of the present study suggest that olfactory identification ability may be a relatively stable indicator of OCD, independent of age, duration of illness, verbal and visual memory, and severity of clinical symptoms.

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

ImportanceOlfactory 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.ObjectiveTo investigate the association between serum concentrations of C-reactive protein (CRP) and olfactory identification level as well as rate of change in aging.MethodsWe 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.ResultsResults 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).ConclusionsOur findings suggest a negative association between serum CRP levels and olfactory identification ability in aging that may be dependent on age and sex.

Olfactory impairment in Wilson’s disease

IntroductionOlfactory dysfunction is a common and early sign of many neurodegenerative disorders, but little is known about olfactory dysfunction in Wilson’s disease (WD). We aimed to evaluate olfactory function in patients with WD and identify selective WD screening odors.MethodsWe measured olfactory identification ability in 25 patients with WD and 25 healthy controls using the University of Pennsylvania Smell Identification Test (UPSIT). Patients with WD were evaluated using the Global Assessment Scale for WD (GAS). Cognitive function was measured using the Mini–Mental State Examination.ResultsPatients with WD were worse at identifying smells in the simplified Chinese version of the UPSIT compared with healthy controls (t = 2.198, p = .033), but there was no difference in olfactory dysfunction severity between the groups (V = 136, p = .094). UPSIT scores negatively correlated with the GAS neurological scores in patients with WD (r = −0.571, p = .003). Using logistic regression with least absolute shrinkage and selection operator analysis, two models were screened. Receiver‐operating characteristic (ROC) curve analysis revealed that, to discriminate WD patients from healthy controls, the area under the ROC curve (AUC) for a combination of seven odors (motor oil, onion, licorice, strawberry, tire, jasmine, and natural gas) was 0.926, while the AUC for three odors (onion, licorice, and jasmine) was 0.852.ConclusionsPatients with WD may have stable, selective olfactory impairments. This selective pattern may be a useful tool for disease diagnosis and prediction.

Olfactory Identification in Subjective Cognitive Decline: A Meta-Analysis.

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. The aim of this meta-analysis was to verify whether the presence of SCD is associated with a decrease in olfactory identification ability. 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. 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]). 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.

Associations of olfaction with mild cognitive impairment and cognitive function in older adults: A population‐based study

AbstractBackgroundOlfactory function might be impaired in the early stage of the dementing process, and thus, olfactory test may be useful for identifying elderly persons at an increased risk. However, previous studies that investigate the relationship between olfactory function and cognitive phenotypes have been scarcely conducted among older people living in the rural communities and the associations of olfaction with specific cognitive remains unclear. We sought to examine the relationship of olfactory function with global cognitive ability and various domains of cognitive function among rural‐dwelling Chinese older adults.MethodThis population‐based cross‐sectional study included 3003 dementia‐free participants (age ≥65 years; 57.3% women; 37.7% illiterate) in the baseline examination (March‐September 2018) of the Multidomain Interventions to Delay Dementia and Disability in Rural China (MIND‐CHINA) study. The 16‐item Sniffin’ Sticks identification test (SSIT) was performed to assess olfactory function. Global cognitive function was evaluated with the Chinese version of the Mini‐Mental State Examination (MMSE) and a neuropsychological battery was used to assess memory, language, attention, and executive function. We followed the Petersen’s criteria to define mild cognitive impairment (MCI). Data were analysed with multiple logistic regression and the general linear regression models.ResultOf the 3003 participants, MCI was defined in 335 persons (11.2%). Multiple logistic regression analysis suggested that SSIT score (range 0‐16) was associated with an odds ratio of 0.90 (95% CI 0.87‐0.93) for MCI. Multiple general linear regression analysis showed that SSIT score was significantly associated with the scores of MMSE test (β coefficient=0.07, 95% CI 0.03‐0.11), z‐score of memory (β coefficient=0.28, 95% CI 0.12‐0.45), language (β coefficient=0.35, 95% CI 0.17‐0.52), and attention (β coefficient=0.59, 95% CI 0.38‐0.78), but not with the z‐score of executive function (β coefficient=0.05, 95% CI ‐0.11‐0.22).ConclusionA greater olfactory identification ability is associated with a lower likelihood of MCI and better performances in global cognitive function, attention, memory, and language function, but not in executive function, among Chinese older adults who are living in the rural communities with limited education.

Early-Onset Schizophrenia Showed Similar but More Severe Olfactory Identification Impairment Than Adult-Onset Schizophrenia.

Background“Early-onset schizophrenia” (EOS) is defined as disease with onset before the age of 18 years. This subset of schizophrenia exhibits worse cognitive function and carries a worse prognosis than adult-onset schizophrenia (AOS). Olfactory impairment has been found in patients with schizophrenia-spectrum disorders. However, most research has focused on olfactory impairment in patients with AOS: olfactory function in EOS is not known. The aim of this study was to investigate the olfactory identification ability in EOS, and its relationship with negative symptoms.MethodsWe compared olfactory function between two independent samples: 40 patients with EOS and 40 age- and sex-matched healthy controls (HCs); as well as 40 patients with AOS and 40 age- and sex-matched HCs. The University of Pennsylvania Smell Identification Test was administered.ResultsThe EOS group and AOS group exhibited worse olfactory identification ability than HCs; impairment correlated significantly with negative symptoms. Olfactory identification was worse in patients suffering EOS compared with those suffering AOS.ConclusionOlfactory identification impairment may be a trait marker of schizophrenia.