Odor Identification Research Articles

Identifying the potential role of serum miR-20a as a biomarker for olfactory dysfunction in patients with Parkinson's disease.

Olfactory dysfunction (OD), one of the most common non-motor symptoms in Parkinson's disease (PD), is a cardinal prodromal symptom that can appear years before the onset of motor symptoms. Ongoing studies have demonstrated that microRNAs (miRNAs) are suitable biomarkers for PD, while there is a lack of robust miRNAs that can serve as markers for OD in PD. The concordantly differentially expressed miRNAs (DE miRNAs) in the damaged olfactory system were first identified in 2 OD-related Gene Expression Omnibus (GEO) datasets. Then, they were verified in another PD-related GEO dataset and only one miRNA (miR-20a) was found to be significantly altered. Serum levels of miR-20a were further measured by qPCR in 79 PD patients with OD (PD-OD), 52 PD patients without OD (PD-NOD), and 52 healthy controls (HC). Objective measure of OD was defined by 16-item Sniffin' Sticks odor identification test. All the participants underwent a demographic and comprehensive PD-related clinical assessment. Our results proved that miR-20a was significantly downregulated in PD-OD compared with PD-NOD and the area under curve (AUC) for OD detection by miR-20a was 0.803 (95% confidence interval, 0.724-0.883). In addition, PD-OD had higher scores of Movement Disorder Society-Unified Parkinson's Disease Rating Scale (UPDRS) II, Hoehn and Yahr stage (H-Y), Non-Motor Symptoms Scale (NMSS) 3, NMSS 5, NMSS 9, Hamilton Rating Scale for Depression (HAMD), Hamilton Anxiety Scale (HAMA), Activity of Daily Living (ADL), and lower scores of Mini-Mental State Examination (MMSE) and 39-item PD Quality of Life Questionnaire (PDQ-39) than PD-NOD. Binary regression model further presented that lower expressions of miR-20a and poorer cognitive function acted as promoting factors in the development of OD. Our results suggest that miR-20a could be a novel biomarker for OD in PD and PD-OD patients tend to have higher disease stage, poorer motor aspects of experiences of daily living, worse cognitive scores, and inferior quality of life, and were more likely to have mental disorders. Cognitive function, in particular, is strongly associated with OD in PD patients.

Brief Test of Olfactory Dysfunction Based on Diagnostic Features of Specific Odors in Early-Stage Alzheimer Disease.

BACKGROUND Olfactory impairment is an early symptom of Alzheimer disease (AD). However, it is rarely assessed in clinical practice. This study aimed to assess the identification and discrimination of specific odors in patients with early-stage AD using the Sniffin' Sticks test and determine the items that would be most valuable in the diagnosis of early-stage AD in order to create a brief test of olfactory dysfunction. MATERIAL AND METHODS Three groups of participants were enrolled, including 30 patients with mild cognitive impairment due to AD (MCI-AD group), 30 with mild dementia due to AD (MD-AD group), and 30 older participants with normal cognition (NC group). All participants underwent cognitive (Clinical Dementia Rating, Mini-Mental State Examination, Alzheimer's Disease Assessment Scale-Cognitive Subscale, and verbal fluency tests) and olfactory (Burghart Sniffin' Sticks odor identification and odor discrimination tests) assessments. RESULTS The MD-AD group scored significantly lower than the MCI-AD group and the MCI-AD group scored significantly lower than the NC group in both the odor identification (P<0.001) and discrimination (P<0.05) tasks. The shortened versions of the odor identification and discrimination tasks showed good diagnostic properties in differentiating patients with AD from the NC participants (receiver operating characteristic [ROC] area under the curve [AUC]=0.912 and 0.954, respectively) and differentiating patients with MCI-AD from the NC participants (ROC AUC=0.871 and 0.959, respectively). CONCLUSIONS The brief versions of olfactory tests, containing selected items that were found to differ the most between cognitively normal participants and early-stage AD patients, have good diagnostic qualities and can aid clinicians in screening for early-stage AD.

Odor-evoked memories: The importance of choosing the right odor

Odors are known to entertain a special link with memory. However, the scientific literature investigating odors as powerful reminders of past experiences shows mixed results. This can be partly due to poor consistency in methodological approaches, especially concerning stimuli choice. Here, we presented 64 odorants to 130 young adults and asked them to freely report what each odor evoked to them. Responses were sorted in 1) mere odors' identification attempts and 2) any other memory-based verbal content, whose phenomenological properties were analyzed quantitatively and qualitatively. As expected, only a limited number of odors managed to spontaneously trigger high-quality autobiographical memories. In most cases, people engage in an odor identification task or evoke unspecific memory contents. We finally selected a pool of 20 odors as a function of the memory contents they're more likely to trigger. This enabled us to formulate recommendations for professionals (researchers or practitioners) performing olfactory-based memory stimulation.

The Effect of Methylphenidate Treatment on Olfactory Function in Children and Adolescents With ADHD

Objective: This study aimed to research whether there is an olfactory disorder in ADHD, and if so, what is the effect of methylphenidate on this condition. Method: This is a cross-sectional study aiming to evaluate olfactory threshold, identification, discrimination and threshold, discrimination, and identification (TDI) scores in 109 children and adolescents, 33 of whom have ADHD without medication, 29 with ADHD with medication and 47 control groups. Result: In the post hoc tests, the mean odor discrimination test, the mean odor identification test, and the mean TDI scores of the unmedicated ADHD group were significantly lower than those of the other two groups, and that the mean odor threshold test scores of the medicated ADHD group were significantly lower than those of the control and unmedicated groups. Conclusion: Olfactory function could be a useful tool to monitor treatment effects and may be a promising candidate as a biomarker in ADHD.

Correction to Leonhardt et al. (2019).

A sample of 124 nondemented PD patients and 154 elderly controls was assessed with the Sniffin' Sticks Odor Identification Test (OIT) and the Subjective Olfactory Capability (SOC) domain of the Assessment of Self-Reported Olfactory Functioning and Olfaction-Related Quality of Life, additional to measures of depressive symptoms, verbal memory and executive functioning. Olfactory awareness groups were formed by means of the cut-offs of the OIT and the SOC. Significant correlations between the OIT and the SOC were moderate in participants with PD and small in controls. Of all PD patients, 52% overrated their sense of smell while 27% correctly identified themselves as being hyposmic, as opposed to corresponding 6% and 1% of healthy elderly. Overrating and aware of being hyposmic participants with PD showed worse executive functions than PD patients who were objectively and subjectively normosmic. The findings imply that, although people with PD are aware of hyposmia to some extent, the majority is affected by overestimation of the ability to smell, making self-reported functioning an unreliable source of information. Moreover, reduced odor identification and impaired executive functioning might underlie the same pathological changes within the brain and could serve as a marker for cognitive impairment in PD. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Olfactory dysfunction in patients with Wilson's Disease.

Many neurodegenerative disorders are associated with olfactory dysfunction (OD), but little is known about OD in Wilson's Disease (WD). We evaluated olfactory function in patients with WD. OD was examined in 68 patients with WD and 70 sex- and age-matched healthy controls using subjective testing with 'Sniffin Sticks'. Threshold discrimination identification (TDI) score and its three components (odour detection threshold, discrimination, and identification) were assessed. Compared to controls, patients with WD had a significantly weaker sense of smell in terms of TDI (p < 0.01), odour discrimination (p < 0.01), and identification (p < 0.01), but not in terms of odour detection threshold (p = 0.27). Patients with predominantly neurological symptoms were characterised by greater OD by TDI (p < 0.01), odour detection threshold (p = 0.01), and discrimination (p = 0.03). The presence of pathological lesions (p = 0.04) in brain magnetic resonance imaging and generalised brain atrophy (p = 0.02) predisposed to worse TDI. In the WD group, weak inverse correlations between age and TDI score (r = -0.27), odour detection threshold (r = -0.3), and discrimination (r = -0.3) were found. Male gender was a risk factor for abnormal TDI in both WD and controls (both p = 0.02). Patients with WD, particularly older individuals, more frequently had OD than healthy volunteers. Predominantly neurological symptoms, and the presence of typical brain MRI changes, predisposed patients with WD to smell disorders.

The Use of Field Olfactometry in the Odor Assessment of a Selected Mechanical–Biological Municipal Waste Treatment Plant within the Boundaries of the Selected Facility—A Case Study

Odor management plans indicate the need to identify odor sources in waste management facilities. Finding the right tool for this type of task is a key element. This article covers a new approach for odor quantification and source identification at a selected waste management facility by coupling field olfactometry and the spatial interpolation method, such as inverse weighted distance. As the results show, this approach works only partially. Field olfactometry seems to be a suitable tool for odor identification that could be an instrument incorporated into odor management plans as it allowed for recognition of most odor-generating places at the selected facility, i.e., waste stabilization area, green waste storage area, and bioreactors. However, spatial distributions obtained by the selected interpolation method are characterized by high errors during cross-validation, and they tend to overestimate odor concentrations. The substantial weakness of the selected interpolation method is that it cannot handle points where the odor concentration is below the detection threshold. Therefore, the usefulness of such a method is questionable when it comes to odor management plans. Since field olfactometry is a reliable tool for odor measurements, further research into computational methods is needed, including advanced interpolation methods or dispersion modeling based on field olfactometry data.

The effects of cognition, quality of life, and fatigue on olfactory function in patients with multiple sclerosis

AimThe frequency of olfactory dysfunction in patients with Multiple Sclerosis (MS) has revealed very different results in studies. Some studies have shown that olfactory dysfunction may be associated with cognitive impairment and poor quality of life. In these studies, different odor tests and cognitive tests were used and different results were obtained. Materials and methodsForty literate patients over the age of 18 and 24 healthy volunteers of similar age and education were included in the study. Sniffin' Sticks Odor Test, California Verbal Learning Test II, Symbol Digit Modalities Test, Revised Brief Visuospatial Memory Test, Trail-Making Test, Quality of Life Short Form-36, Fatigue Impact Scale, Beck Depression Inventory, and Beck Anxiety Inventory were applied to the individuals. ResultsOlfactory dysfunction was detected in 50 % of the patients. High disability rate, low cognitive functions, low quality of life, and fatigue were identified as the factors affecting olfactory function negatively. Odor discrimination and identification abilities were associated with disability level and cognitive functions, whereas quality of life was linked to odor threshold scores. The olfactory function and cognitive abilities of patients with progressive MS (n = 5) were worse than those of patients with relapsing remitting MS (n = 35). ConclusionOlfactory dysfunction is common in patients with MS and is associated with disability and quality of life. Olfactory function can be used in the follow-up of patients and olfactory dysfunction deserves further study as a metric that might emerge as a biomarker.

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.

E-Nose design and structures from statistical analysis to application in robotic: a compressive review

Since 1982, the olfactory system of creatures has piqued the interest of academics who seek to create a comparable system. Despite its mysterious nature, the first stage has been successfully completed with the development of the E-nose. Its extended applications have opened new doors for researchers, ranging from food quality testing to bomb detection and even, more recently, identifying those infected with the coronavirus. In this talk, we will review the structure and sensor behavior of the E-nose, as well as its applications, such as odour source localization and various applications in agriculture. The challenge of odour identification has prompted researchers to employ robots with sensors to investigate and locate odour sources. The present study aims to synthesize documented research and provide a fresh perspective on odour localization research efforts and tests conducted. The study highlights previous attempts to equip robots with sensors to explore the real indoor or outdoor environment. Initially, a review was conducted to investigate various aspects of the sector and the obstacles involved.

Olfactory and gustatory outcomes following endoscopic transsphenoidal hypophysectomy

ObjectiveThe aim of this study was to evaluate olfactory, gustatory, and quality-of-life outcomes in patients who underwent endonasal transsphenoidal hypophysectomy.MethodsIn this prospective study, the patients were assessed subjectively using the Malay version of sQOD-NS (short questionnaire of olfactory disorders in a negative statement) and objectively using the culturally adapted Sniffin’ Sticks smell test and taste test preoperatively and 3 months postoperatively. The Sniffin’ Sticks smell test consists of odor identification, odor discrimination, and odor threshold tests. The taste test consists of different sweet, salt, sour, and bitter concentrations.ResultsTwenty patients were enrolled in the study. The study comprises 45% female and 55% male. On average patients’ ages were 49.5 years. In this study we found a significantly reduced in odor identification score (p = 0.049) post-surgery; however, there was no statistically significant difference in odor threshold, odor discrimination, and taste. The olfactory quality of life outcome based on the Malay version of sQOD-NS (p = 0.001) was significantly reduced after surgery. There was no significant difference in the Sniffin’ Sticks smell test (p < 0.178) and taste test (p < 0.425) pre-surgery and post-surgery. The tumor’s location, either sellar or suprasellar, did not influence the smell outcome of patients postoperatively (p = 0.056).ConclusionThe study showed that the endoscopic transsphenoidal technique for pituitary surgery does not pose permanent olfactory disability.

Properties of odor identification testing in screening for early-stage Alzheimer’s disease

Odor identification (OI) is impaired in the early stages of Alzheimer’s disease (AD). However, data regarding the diagnostic properties of OI tests are lacking, preventing their clinical use. We aimed to explore OI and determine the accuracy of OI testing in screening for patients with early AD. In total, 30 participants with mild cognitive impairment due to AD (MCI-AD), 30 with mild dementia due to AD (MD-AD), and 30 cognitively normal elderly participants (CN) were enrolled, and cognitive examination (CDR, MMSE, ADAS-Cog 13, and verbal fluency tests) and assessment of OI (Burghart Sniffin’ Sticks odor identification test) were performed. MCI-AD patients scored significantly worse in OI than CN participants, and MD-AD patients had worse OI scores than MCI-AD patients. The ratio of OI to ADAS-Cog 13 score had good diagnostic accuracy in differentiating AD patients from CN participants and in differentiating MCI-AD patients from CN participants. Substitution of ADAS-Cog 13 score with the ratio of OI to ADAS-Cog 13 score in a multinomial regression model improved the classification accuracy, especially of MCI-AD cases. Our results confirmed that OI is impaired during the prodromal stage of AD. OI testing has a good diagnostic quality and can improve the accuracy of screening for early-stage AD.

Gender-Related Differences in the Correlation between Odor Threshold, Discrimination, Identification, and Cognitive Reserve Index in Healthy Subjects.

Many studies suggested that olfactory function could be associated with semantic memory, executive function, and verbal fluency. However, the gender-related association between olfactory function and the cognitive domain is not well investigated. The aim of this study was to estimate gender-related differences in the relationship between olfactory function and each specific cognitive domain of the Cognitive Reserve Index (CRI) questionnaire, such as education, working activity, and leisure time in healthy subjects. Two hundred and sixty-nine participants were recruited (158 women and 111 men), with a mean age of 48.1 ± 18.6 years. The CRI questionnaire and Sniffin' Sticks test were used to evaluate the cognitive reserve and the olfactory function, respectively. In all subjects, significant associations between the odor threshold versus CRI-Education, between the odor discrimina-tion and identification versus CRI-Working activity and CRI-Leisure Time, were found. In women, odor threshold, discrimination, and identification were associated with CRI-Leisure Time, while in men, only a significant association between odor threshold and CRI-Education was observed. Our data, showing significant gender-related associations between olfactory function and CRI scores, suggested the use of olfactory evaluation and cognitive reserve as an important screening tool for the early detection of mild cognitive impairment.

Odor identification errors reveal cognitive aspects of age-associated smell loss

Human olfaction can be extraordinarily sensitive, and its most common assessment method is odor identification (OID), where everyday odors are matched to word labels in a multiple-choice format. However, many older persons are unable to identify familiar odors, a deficit that is associated with the risk of future dementia and mortality. The underlying processes subserving OID in older adults are poorly understood. Here, we analyzed error patterns in OID to test whether errors could be explained by perceptual and/or semantic similarities among the response alternatives. We investigated the OID response patterns in a large, population-based sample of older adults in Sweden (n = 2479; age 60–100 years). Olfaction was assessed by a ‘Sniffin ́ TOM OID test with 16 odors; each trial involved matching a target odor to a correct label among three distractors. We analyzed the pattern of misidentifications, and the results showed that some distractors were more frequently selected than others, suggesting cognitive or perceptual factors may be present. Relatedly, we conducted a large online survey of older adults (n = 959, age 60–90 years) who were asked to imagine and rate the perceptual similarity of the target odors and the three corresponding distractors (e.g. “How similar are these smells: apple and mint?”). We then used data from the Swedish web corpus and the Word2Vec neural network algorithm to quantify the semantic association strength between the labels of each target odor and its three distractors. These data sources were used to predict odor identification errors. We found that the error patterns were partly explained by both the semantic similarity between target-distractor pairs, and the imagined perceptual similarity of the target-distractor pair. Both factors had, however, a diminished prediction in older ages, as responses became gradually less systematic. In sum, our results suggest that OID tests not only reflect olfactory perception, but also likely involve the mental processing of odor-semantic associations. This may be the reason why these tests are useful in predicting dementia onset. Our insights into olfactory-language interactions could be harnessed to develop new olfactory tests that are tailored for specific clinical purposes.

The effect of nasal surgeries on olfactory functional outcome

Abstract Background: Nasal pathologies can alter the olfactory function there by the quality of life. In this study, we did an olfactory assessment in patients undergoing nasal surgeries, and the preoperative values were compared with the postoperative values. Objective: The objective of the study is to assess the role of nasal surgeries on olfactory functions in patients with nasal pathologies. Materials and Methods: In total, 70 participants undergoing nasal surgeries were subjected to olfactory function assessment using the Modified I smell test, which comprises olfactory threshold testing and odor identification, and the Numerical Rating Scale. Olfactory assessment was done preoperatively, 4th week and 12th week after the surgery. Results: Among 70 cases, 18 were sinonasal polyposis (25.75%), 16 (22.85%) were chronic rhinosinusitis cases, 35 (50%) deviated nasal septum cases and only one (1.4%) bilateral inferior turbinate hypertrophy case. The overall mean preoperative combined olfactory score (COS) value was 16.03 ± 2.55, 18.06 ± 1.68 in the 4th week of the postoperative period, and in the 12th week, it was 17.99 ± 1.83. There was a significant improvement in olfactory function when preoperative COS was compared with postoperative COS in different nasal surgeries. The olfactory impairment in nasal polyposis and chronic rhinosinusitis was more when compared to other nasal pathologies like nasal obstructions due to deviated nasal septum and turbinate hypertrophy. Overall, 91.7% of participants who underwent functional endoscopic sinus surgery (FESS) and 90% of FESS + septoplasty cases showed improvement in olfactory function. Only 50% of septoplasty cases showed improvement. Conclusion: Nasal pathologies are more common among men of the age group 21–30 years. Olfactory impairment in nasal polyposis and chronic rhinosinusitis was more compared to other nasal pathologies like nasal obstructions due to deviated nasal septum. FESS significantly improves the olfactory function in chronic rhinosinusitis and sino-nasal polyposis patients.

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.

Ortho‐ and Retronasal stimulations with specific food odours: Hedonic and familiarity ratings are related to chemosensory pleasure scale (CPS) scores

AbstractVolatile compounds can reach olfactory epithelium though the nose (orthonasal olfaction) or the mouth (retronasal olfaction). Although differences have been found between these two pathways in terms of odour sensitivity and identification, few studies have examined ortho‐ and retronasal differences taking into consideration the three main dimensions of olfactory perception (i.e. hedonicity, intensity and familiarity). Olfactory perception, and particularly odour hedonic perception, is influenced by several factors such as sex or age. Another variability factor worth considering, especially regarding food‐related odours, is the ability to experience pleasure simulated by smell or taste, which can be measured with the Chemosensory Pleasure Scale (CPS). Thus, the aims of this study were (1) to compare odour sensory ratings in response to ortho‐ and retronasal presentation and (2) to examine the relationship between CPS scores and odour sensory ratings in ortho‐ and retronasal pathways. Participants rated ten food odours in ortho‐ and retronasal conditions using visual analogue scales and were divided into two subgroups based on the median CPS score (CPS+ and CPS− groups). Results revealed similar sensory responses to food odours between ortho‐ and retronasal pathways for the three main dimensions of olfactory perception. Interestingly, when CPS scores were considered, clear differences in odour familiarity and hedonicity were shown, particularly for the retronasal pathway (i.e. odours were perceived as more pleasant and more familiar in CPS+ group than in CPS− group). Overall, these findings suggest that differences in odour perception between ortho‐and retronasal pathways may be related to specific individual characteristics such as chemosensory hedonic capacity.

The effect of post-COVID-19 on gustatory and olfactory function: A preliminary case-controlled study.

The aim of the study was to analyze objective and subjective olfactory/gustatory function in post-COVID-19 infection (PCI). Patients with past PCR-confirmed COVID-19 infection and persistent olfactory/gustatory complaints were investigated. Olfactory threshold and identification, gustatory detection, identification, and magnitude scaling were tested. A total of 42 PCI subjects were compared to 41 age- and gender-matched controls with no COVID-19 history. All PCI tested had mild COVID-19 disease. Mean interval between COVID-19 confirmations to testing was 7.4 ± 3.1 months. PCI subjects complained of combined dysfunction in 85.7%, isolated olfactory or gustatory dysfunction in 7.1% each. Combined complaints were significantly higher in PCI (p < 0.001). Objective testing showed significantly higher prevalence of dysfunction in PCI versus controls for hyposmia (73.8%, 12.2%), anosmia (11.9%, 0%), odor identification (68.5%, 83.0%), hypogeusia (23% and 2.4%, respectively), and impaired magnitude scaling, (p < 0.05). All PCI subjects with hypogeusia had abnormal gustatory magnitude scaling. While most PCI subjects complained of combined gustatory and olfactory dysfunction, objective testing showed in the majority an isolated single sense dysfunction, with a low level of agreement between subjective and objective findings. Abnormal objective results for all olfactory and gustatory functions tested may suggest a central rather than peripheral mechanism, although concomitant mechanisms cannot be excluded.

Deficits in odor discrimination versus odor identification in patients with schizophrenia and negative correlations with GABAergic and DNA methyltransferase mRNAs in lymphocytes.

People with schizophrenia have been reported to show deficits in tests of olfactory function. DNA methylation and GABAergic input have been implicated in biochemical processes controlling odor in animal studies, but this has not been investigated in human studies. In a study of measures of DNA methylation and GABAergic mRNAs in lymphocytes, we also measured odor identification and discrimination with the Sniffin' Sticks battery in 58 patients with chronic schizophrenia (CSZ) and 48 controls. mRNAs in lymphocytes were assessed by qPCR using TaqManTM probes. Cognition was assessed by the MATRICS battery (Measurement and Treatment Research to Improve Cognition in Schizophrenia) in CSZ and controls, and symptoms in CSZ were assessed by PANSS scale (Positive and Negative Symptom Scale). The relationships of odor deficits with mRNA, cognition, and symptoms were explored by correlation analysis. Variables which significantly differentiated CSZ from controls were explored by logistic regression. Overall, CSZ showed significantly (P≤.001) lower scores on odor discrimination compared to controls, with a moderate effect size, but no difference in odor identification. Deficits in odor discrimination, which has not been standardly assessed in many prior studies, strongly differentiated CSZ from controls. In logistic regression analysis, odor discrimination, but not odor identification, was a significant variable predicting schizophrenia versus control class membership. This is the first study to report relationship between odor deficits and DNA methylation and GABAergic mRNAs in blood cells of human subjects. There were negative correlations of odor identification with DNA methylation enzymes mRNAs and significant negative correlations with odor discrimination and GABAergic mRNAs. Lower odor scores were significantly associated with lower cognitive scores on the MATRICS battery in CSZ but not control subjects. In CSZ, lower odor scores were significantly associated with negative symptom scores, while higher odor identification scores were associated with PANNS Excitement factor. Odor discrimination was a more powerful variable than odor identification in discriminating CSZ from controls and should be used more regularly as an odor measure in studies of schizophrenia. The substantive meaning of the negative correlations of odor discrimination and GABAergic mRNA variables in peripheral lymphocytes of CSZ needs more investigation and comparison with results in neural tissue.

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.