Associations Between Cognitive Function, Depression, and Olfactory Function in Elderly People With Dementia in Korea

Early detection is important for delaying or preventing cognitive impairment. Since olfactory dysfunction and depression are common symptoms of cognitive dysfunction, they may serve as measurable risk indicators. This study was designed to identify the relationship between olfaction, depression, and each domain of cognitive function in elderly dementia patients in South Korea. Study participants were 108 patients who visited the outpatient clinic between March and September 2019. More significant impairment of olfactory function was found in those with mild (7.48 ± 1.28) or moderate (7.37 ± 2.22) test scores of the Expanded Clinical Dementia Rating (CDR) scale than in those with questionable scores (20.58 ± 6.18). The language domain of cognitive function, age, and education level showed 39.2% explanatory power for olfactory function (F = 5.591, p < 0.001). It is expected that assessment of olfactory function in elderly people can lead to the early detection, diagnosis, and treatment of dementia. Furthermore, it is important for future studies to confirm the relationship between each domain of cognitive function and olfactory function according to the type of dementia and to establish criteria for screening dementia in order to utilize olfactory function as a clinical marker.

Validation of the local applicability of the ‘TIB’ Olfactory Test Device in the era of COVID-19

Objective To evaluate the validity and test–retest reliability of the novel ‘TIB’ Olfactory Test Device (TIB) and to determine its normative values. Methods The study stratified the study subjects into normosmic, hyposmic and anosmic groups according to their olfactory function. The olfactory function of the subjects was evaluated using both the traditional Chinese version of the University of Pennsylvania of Smell Identification Test (UPSIT-TC) and the TIB. The normosmic group was used to retest with the UPSIT-TC and TIB at an inter-test interval of at least 7 days. The cut-off scores of TIB among the three different groups were determined by receiver operating characteristic curve analysis. Results This study enrolled 180 subjects: 60 in each group. The mean scores of TIB were 44.1 for the normosmic group, 27.5 for the hyposmic group and 10.9 for the anosmic group. The TIB scores were significantly different across the three groups. There was a significant correlation between the first and second TIB tests ( r = 0.506). The cut-off scores were 41 for normosmic subjects and 24 for hyposmic subjects. Conclusion The validity and test–retest reliability results suggest that the TIB is an appropriate olfactory test for the Taiwanese population.

High prevalence of long-term olfactory dysfunction confirmed by olfactory testing after a community COVID-19 outbreak

Purpose The prevalence of long-term olfactory and gustatory dysfunction in participants suffering from sudden chemosensory loss due to coronavirus disease 2019 (COVID-19) is unknown. Furthermore, evaluations of the reliability of participants’ self-reporting of olfactory function (SOF) and gustatory function (SGF) using extended objective psychophysical testing are missing. Methods In this population-based cohort study in a PCR-tested community in Thuringia, Germany, olfactory function was extensively examined 4 months after a COVID-19 outbreak using the “Sniffin Sticks” test battery to determine the TDIa score, i.e., the sum of results obtained for threshold, discrimination, and identification scores averaged for both nasal sides. Gustatory function was assessed using the three-drop test resulting in the gustatory composite score (CSg). The data were compared with SOF and SGF. Results Of 43 adult convalescents (median age: 68 years; 58% female) after SARS-CoV‑2 infection, 18 participants (42%) had olfactory complaints due to SOF, one participant (2%) complained of taste disturbance due to SGF. The TDIa was 22.0 ± 5.9. Normosmia, hyposmia, and anosmia were seen in 17, 18, and eight participants, respectively. TDIa correlated with SOF (rs = −0.434, p = 0.004); CSg was 23.5 ± 2.7. Normogeusia and hypogeusia were objectified in 39 and four participants, respectively. The prevalence of long-term olfactory dysfunction and gustatory dysfunction in the study group was 60.5 and 9.3%, respectively. Conclusion The SOF was reliable, especially for participants who felt a sudden chemosensory dysfunction during the outbreak. At 4 months after SARS-CoV‑2 infection, a high proportion of participants were dysosmic, whereas nearly all of them had normal taste function.

Olfactory Function, Genetic Predisposition, and Cognitive Performance in Chinese adults

Objective: The objective of this study is to examine the association of olfactory function and genetic predisposition of Alzheimer’s disease (AD) with cognitive performance in adults. Methods: A total of 2049 Chinese adults from Rugao Longevity and Ageing Study (RuLAS, n=1460, mean age 78 years) and Central China Cohort (CCC, n=589, mean age 48 years) were included in this study. A standard interview-based survey, clinical information, and blood samples were collected in both cohorts. Olfactory function in terms of olfactory identification was measured by the brief version of the Chinese Smell Identification Test consisted of 18 full points. Cognitive performance was measured by the Chinese version of the Mini-mental State Examination. A genetic risk score (GRS) was calculated from 5 single nucleotide polymorphisms, which were robustly related to Alzheimer’s disease in Caucasians and cognitive performance in our Chinese population. Results: In the pooled analyses, participants at the lowest quartile of olfactory function had significantly higher odds of cognitive impairment (adjusted odds ratio [95% CI] =1.45 [1.00 to 2.09], Ptrend =0.005), and such association was stronger among participants with a stronger genetic predisposition of Alzheimer’s disease (β coefficient±SE, -0.06±0.03 in participants with a lower GRS vs. -0.19±0.05 in those with a higher GRS, respectively, Pinteraction=0.01). Similar associations were observed in RuLAS (P-trend=0.06) and in CCC (P-trend<0.001). Conclusion: In this study, a decreased olfactory function was associated with worse cognitive performance in adults, especially among participants with a higher genetic risk of Alzheimer’s disease. Further studies are warranted to evaluate the causal relationship between olfaction and cognitive performance.

Reliability and validity of a brief version of the Questionnaire of Olfactory Disorders (brief QOD) in patients with olfactory dysfunction

Background: The aim of this study was to determine the reliability and validity of the brief version of Questionnaire of Olfactory Disorders (brief QOD). Methods: A total of 372 patients participated in this study. Olfactory function was examined using the Sniffin’ Sticks test. The brief version of QOD, including 4 items concerning parosmia (QOD-P), 7 items concerning quality of life (QOD-QOL), and 3 visual analog scales to rate disease burden, awareness of the disorder and issues related to professional life (QOD-VAS), was used to assess subjective information on olfactory dysfunction. We evaluated the split-half reliability, internal consistency and validity of the brief QOD. Results: The split-half reliability was 0.60 (QOD-P), 0.87 (QOD-QOL), and 0.66 (QOD-VAS), respectively. The Cronbach’s α coefficient was 0.63 (QOD-P), 0.87 (QOD-QOL), and 0.71 (QOD-VAS), respectively. Olfactory function was found to be associated with QOD-P, QOD-QOL and QOD-VAS. Conclusions: The brief QOD is a suitable scale for the assessment of subjective severity of olfactory dysfunction for purposes such as treatment counseling, disability assessment, treatment control, and research in patients with olfactory disorder.

Olfactory function testing before and after anesthesia

This study aimed to determine whether anesthesia would affect olfactory function. Patients who were admitted for surgical intervention that did not include the nasal cavity and paranasal sinuses were included in this prospective cohort study. Structured medical history was taken from the patients, including the following: age, sex, smoking history, alcohol intake, current medications, and sleep deficits prior to surgery. Before surgery, patients were asked for a self-rating of their olfactory function. Olfactory function was also measured using Sniffin’ Sticks comprising measures of odor threshold, discrimination, and identification. The mean interval between olfactory tests was 6 days (range 3–12 days). Seventy-three patients were included in the study, 34 men and 39 women. Olfactory scores were consistent before and after surgery as indicated by correlative analyses (p < 0.05). Odor thresholds, discrimination, identification, and composite TDI scores did not change significantly, whereas odor identification scores increased (p = 0.011) after surgery. In conclusion, post-operative olfactory scores remained stable. However, identification scores exhibited a slight increase which can be attributed to a retest effect. Overall, the present results indicate that surgery outside of the nasal and paranasal sinus region performed in general anesthesia has no major effect on the sense of smell.