The effect of smell training on COVID-19 induced smell loss.

OBJECTIVE: while smell training appears to be effective for post viral smell loss, its effectiveness in COVID-19 induced smell loss is currently not well known. Therefore, we aim to investigate the potential effect of smell training on patients with COVID-19 induced smell loss. METHODS: we conducted a case-control study with two comparable cohorts. One of which (n=111) was instructed to perform smell training twice daily for 12 weeks, therapeutical adherence was monitored on a daily schedule, while the other cohort (n=50) did not perform smell training. The Sniffin' Sticks Test (SST) was used to objectify participants' sense of smell at baseline and after 12 weeks, reported as a Threshold, Discrimination, and Identification (TDI) score. We also determined the association between therapeutical adherence and the TDI scores. RESULTS: we found a significant difference in psychophysical smell function between patients with COVID-19 induced smell disorders who performed 12 weeks of smell training and those who did not. Median TDI difference between groups was 2.00 However, there was no association between the therapeutical adherence and olfactory function. CONCLUSION: we discovered a significant moderate difference in psychophysical smell function between patients with COVID-19-induced smell disorders who performed smell training and those who did not, implying a possible advantage of training. However, no relationship was found between therapeutical adherence of smell training and olfactory function.

A follow-up on quantitative and qualitative olfactory dysfunction and other symptoms in patients recovering from COVID-19 smell loss.

BACKGROUND: Sudden smell loss is a specific early symptom of COVID-19, which, prior to the emergence of Omicron, had estimated prevalence of ~40% to 75%. Chemosensory impairments affect physical and mental health, and dietary behavior. Thus, it is critical to understand the rate and time course of smell recovery. The aim of this cohort study was to characterize smell function and recovery up to 11 months post COVID-19 infection. METHODS: This longitudinal survey of individuals suffering COVID-19-related smell loss assessed disease symptoms and gustatory and olfactory function. Participants (n=12,313) who completed an initial survey (S1) about respiratory symptoms, chemosensory function and COVID-19 diagnosis between April and September 2020, were invited to complete a follow-up survey (S2). Between September 2020 and February 2021, 27.5% participants responded (n=3,386), with 1,468 being diagnosed with COVID-19 and suffering co-occurring smell and taste loss at the beginning of their illness. RESULTS: At follow-up (median time since COVID-19 onset ~200 days), ~60% of women and ~48% of men reported less than 80% of their pre-illness smell ability. Taste typically recovered faster than smell, and taste loss rarely persisted if smell recovered. Prevalence of parosmia and phantosmia was ~10% of participants in S1 and increased substantially in S2: ~47% for parosmia and ~25% for phantosmia. Persistent smell impairment was associated with more symptoms overall, suggesting it may be a key marker of long-COVID illness. The ability to smell during COVID-19 was rated slightly lower by those who did not eventually recover their pre-illness ability to smell at S2. CONCLUSIONS: While smell ability improves for many individuals who lost it during acute COVID-19, the prevalence of parosmia and phantosmia increases substantially over time. Olfactory dysfunction is associated with broader persistent symptoms of COVID-19, and may last for many months following acute COVID-19. Taste loss in the absence of smell loss is rare. Persistent qualitative smell symptoms are emerging as common long-term sequelae; more research into treatment options is strongly warranted given that even conservative estimates suggest millions of individuals may experience parosmia following COVID-19. Healthcare providers worldwide need to be prepared to treat post COVID-19 secondary effects on physical and mental health.

The Effect of Food Odor Exposure on Appetite and Nutritional Intake of Older Adults with Dementia.

OBJECTIVES: Dementia can lead to decreased appetite and nutritional intake. Food odor exposure has been shown to increase appetite and nutritional intake in young healthy adults. This study investigates the effect of food odor exposure on appetite, nutritional intake and body weight of Dutch nursing home residents with dementia. DESIGN: This was a one-armed, non-randomized, non-blinded intervention study consisting of a four-week control period followed by a twelve-week intervention period. SETTING: Four nursing homes in the Netherlands. PARTICIPANTS: Forty-five nursing home residents with dementia. INTERVENTION: During the intervention period, odors were dispersed prior to the main meals. MEASUREMENTS: General and specific appetite for sweet and savory foods was measured weekly. Nutritional intake was measured once during the control period and three times during the intervention period through a 3-day food record. Body weight was assessed at the start and end of the control period and at the start, end and halfway the intervention period. Data were analyzed with linear mixed models. RESULTS: Small changes in general and specific appetite were observed after odor exposure. Overall energy intake did not change during the first four intervention weeks, but increased during the second and third (+118kcal/d, p=0.003 and +122kcal/d, p=0.004). Protein intake and body weight did not significantly change during the study. CONCLUSION: In this study, no clinically relevant changes in appetite, nutritional intake and body weight were observed after food odor exposure. Future studies should assess the effect of natural food odors and/or meal-tailored odors on nutritional intake of older adults with dementia.

Investigating morphological changes in the brain in relation to etiology and duration of olfactory dysfunction with voxel-based morphometry.

Olfactory loss (OL) affects up to 20% of the general population and is related to changes in olfaction-related brain regions. This study investigated the effect of etiology and duration of OL on gray matter volume (GMV) of these regions in 257 patients. Voxel-based morphometry was applied to measure GMV in brain regions of interest to test the effects of etiology and duration on regional GMV and the relation between olfactory function and regional GMV. Etiology of OL had a significant effect on GMV in clusters representing the gyrus rectus and orbitofrontal cortex (OFC), bilaterally. Patients with congenital anosmia had reduced GMV in the gyrus rectus and an increased OFC volume compared to patients with acquired OL. There was a significant association between volume of the left OFC and olfactory function. This implies that changes in GMV in patients with acquired OL are mainly reflected in the OFC and depend on olfactory function. Morphology of olfactory areas in the brain therefore seems to relate to olfactory function and the subsequent degree of exposure to olfactory input in patients with acquired OL. Differences in GMV in congenital anosmia are most likely due to the fact that patients were never able to smell.

Chemosensory perception and food preferences in colorectal cancer patients undergoing adjuvant chemotherapy.

BACKGROUND AND AIM: Cancer is one of the major public health problems, with colorectal cancer being one of the most occurring types of cancer. During treatment, patients may experience changes in their dietary intake due to side-effects of treatment, like changes in chemosensory perception, i.e. smell and taste function. This study investigated alterations in chemosensory perception and food preferences in colorectal cancer patients during and after adjuvant chemotherapy. METHODS: Objective olfactory and gustatory function were measured by the Sniffin' Sticks and the Taste Strips test. Subjective smell and taste perception were determined with a questionnaire, while food preferences were assessed with a computer-based ranking task. To investigate changes during chemotherapy, patients undergoing adjuvant chemotherapy were measured before the start, halfway through (approximately 3 months after the start of adjuvant chemotherapy), and within one month after finishing chemotherapy (longitudinal measurements, n = 15 patients). As a comparison group, colorectal cancer patients not undergoing chemotherapy (n = 20), underwent the same measurements at similar time points. To measure changes after treatment, chemosensory perception and food preferences of patients who had undergone chemotherapy treatment were measured once, either at 6, 12 or 24 months after diagnosis (cross-sectional measurements; n = 20 for all time points). Changes during treatment were assessed using linear mixed model analyses, and changes after treatment were assessed with a one-way ANOVA or a Kruskal Wallis test. RESULTS: Objective olfactory and gustatory function did not differ statistically significantly between any of the groups and at any time point during or after treatment (all p > 0.05). In contrast, subjective smell (F(1,84) = 8.17, p = 0.005) and taste (F(1,99) = 4.08, p = 0.046) perception were rated statistically significantly lower by patients undergoing chemotherapy than the comparison group during treatment. At 6 months after diagnosis, patients who underwent chemotherapy rated their subjective taste perception significantly lower than patients at 12 and 24 months after treatment (F(2,57) = 12.05, p = 0.002). Food preferences did not change during treatment, or thereafter (all p > 0.05). Preference for protein-rich foods was positively correlated with objective gustatory function (r = 0.36, p < 0.001), while the preference for low-energy foods showed a negative correlation with objective gustatory function (r = -0.28, p = 0.004). CONCLUSIONS: Similar to other cancer patient populations, mainly subjective smell and taste perception are affected in colorectal cancer patients undergoing adjuvant chemotherapy. Changes in objective olfactory and gustatory function in relation to chemotherapy were not detected by the tests used in our study nor did food preferences change. However, it should be noted that subjective changes in smell and taste perception can affect subsequent flavor perception and food enjoyment, which might negatively impact eating behavior and nutritional intake.

"U-Sniff" - the international odor identification test for children: an extension of its normative database and study of global reliability.

BACKGROUND: To extend the previous study by Schriever and colleagues from 2018 providing normative data and re-investigating the reliability for U-Sniff test in children in additional countries. METHODOLOGY: A total of 388 children (196 boys, 192 girls) from eight countries (China, Germany, Iran, Netherlands, Norway, Oman, Paraguay, and Russia) participated in this study. The children were recruited from public local schools in those particular countries. The odor identification ability was evaluated using the U-Sniff test, a 12-item odor identification test developed for children. In addition, reliability was examined using test-retest design in the children for each country. RESULTS: The mean U-Sniff test score across all children was 10.3 +- 1.7 points. Normative data were established. A high test-retest reliability of the U-Sniff test was demonstrated across the eight participating countries. CONCLUSIONS: The U-Sniff test for children exhibits a high test-retest reliability on a global scale.

Olfactory and gustatory functioning and food preferences of patients with Alzheimer's disease and mild cognitive impairment compared to controls: the NUDAD project.

Our aim is to compare olfactory and gustatory function and food preferences of patients with Mild Cognitive Impairment (MCI) and Alzheimer's disease (AD) with controls. We included 22 patients with MCI, 30 patients with AD and 40 controls and assessed olfactory threshold, odor discrimination and odor identification (Sniffin' Sticks), gustatory functioning (Taste Strips), and food preferences (Macronutrient and Taste Preference Ranking Task). Linear regression analyses were used to study associations of five cognitive domains or AD biomarkers with olfactory functioning. Groups did not differ in olfactory threshold, gustatory function and food preferences. Patients with MCI and AD scored lower on odor discrimination and identification than controls. Poorer memory, but no other cognitive domain, was associated with poorer odor discrimination and odor identification, but not with odor threshold. No associations with AD biomarkers were found. In conclusion, patients with MCI and AD have poorer odor discrimination and identification ability than controls, but similar detection thresholds. This is likely a consequence of poorer memory rather than directly caused by AD pathology.

Low reported taste function is associated with low preference for high protein products in advanced oesophagogastric cancer patients undergoing palliative chemotherapy.

BACKGROUND & AIMS: Cancer patients undergoing palliative chemotherapy can experience a variety of chemosensory and food preference changes which may impact their nutritional status and quality of life. However, evidence of these changes in oesophagogastric cancer (OGC) patients is currently mostly qualitative and not supported by quantitative data. The aim of this study was to assess how self-reported and objective taste and smell function and food preferences change over time during chemotherapy in OGC patients. METHODS: This observational study included 15 advanced OGC patients planned for first line treatment with capecitabine and oxaliplatin. Participants completed two test sessions scheduled before start of cytotoxic treatment and after two cycles. Self-reported and objective taste and smell function and the macronutrient and taste preference ranking task were conducted at each test session. RESULTS: Self-reported taste and smell did not change upon chemotherapy. Objective taste function decreased during chemotherapy, although this was not statistically significant (p = 0.06), objective smell function did not change. Before and during chemotherapy, high protein foods were preferred over high carbohydrate and over low energy products, but food preferences did not change over time. A lower self-reported taste function correlated with a lower preference for high-protein products (ρ = 0.526, p = 0.003). CONCLUSION: This study suggests that objective taste function decreases during chemotherapy in OGC patients, but not smell function. A low reported taste function was related to a lower preference for high-protein products.

Altered neural inhibition responses to food cues after Roux-en-Y Gastric Bypass.

BACKGROUND: Roux-en-Y gastric bypass (RYGB) surgery is a highly effective weight-loss intervention that often reduces preference and intake of high-energy foods. Research into the neural mechanisms behind this shift has mainly focused on reward processing of food cues. However, the ability to successfully control food intake and thereby weight-loss also depends on inhibitory control capacity. We investigated whether RYGB leads to alterations in neural inhibitory control in response to food cues. METHODS: A food-specific go/no-go task with pictures of high-energy (desserts) and low-energy foods (vegetables), was used to assess neural inhibition responses before and after RYGB with functional magnetic resonance imaging. Data from 18 morbidly obese patients (15 females; age 41 ±â€¯11 years; BMI 42 ±â€¯4 kg/m2 before; BMI 36 ±â€¯4 kg/m2 after) were analysed. Pre- and post-RYGB BOLD fMRI responses were compared for response inhibition towards high- and low-energy foods. Participants were tested in a satiated state. RESULTS: Response inhibition to high-energy foods was associated with increased activation of the right lateral prefrontal cortex (PFC), right medial PFC, dorsolateral PFC, right middle cingulate cortex and the right inferior frontal operculum (involved in inhibitory control), after compared to before surgery. Response inhibition to low-energy foods elicited diminished post- compared to pre-surgery responses in the left superior temporal pole, right parahippocampal gyrus and right hypothalamus (involved in metabolic control). CONCLUSION: Neural changes indicate improved response inhibition towards high-energy food cues, altered influence of metabolic control during response inhibition towards low-energy food cues and a more positive attitude to both high-energy and low-energy food after RYGB. Alterations in neural circuits involved in inhibitory control, satiety signalling and reward processing may contribute to effective weight-loss after RYGB.

Taste and smell perception and quality of life during and after systemic therapy for breast cancer.

PURPOSE: The purpose of the study was to assess self-reported taste and smell perception after chemotherapy in breast cancer patients compared with women without cancer, and to assess whether taste and smell perception is associated with quality of life after the end of chemotherapy. METHODS: We included 135 newly diagnosed breast cancer patients who completed chemotherapy and 114 women without cancer. Questionnaires on taste, smell, and quality of life were completed shortly after and 6 months after chemotherapy (patients) or at two moments with 6 months' time window in between (comparisons). RESULTS: Self-reported taste and smell perception were significantly lower in patients shortly after chemotherapy compared to the comparison group. Most patients recovered 6 months after chemotherapy, although patients who were still receiving trastuzumab then reported a lower taste and smell perception compared to patients who were not. A lower self-reported taste and smell were statistically significantly associated with a worse quality of life, social, emotional, and role functioning shortly after chemotherapy. Six months after chemotherapy, taste and smell were statistically significantly associated with quality of life, social and role functioning, but only in patients receiving trastuzumab. CONCLUSIONS: Most taste and smell alterations recovered within 6 months after the end of chemotherapy for breast cancer, but not for patients receiving trastuzumab. These results highlight the importance of monitoring taste and smell alterations during and after treatment with chemotherapy and trastuzumab, as they may impact quality of life.

How to quench your thirst. The effect of water-based products varying in temperature and texture, flavour, and sugar content on thirst.

The sensation of thirst plays an important role in the consumption of water or other fluids to rehydrate the body in order to keep bodily functions working properly. An increase in saliva secretion, wetting the mouth by ingestion of liquids, and cooling and sour components in products can alleviate this sensation already before absorption of fluids by the body. This study aimed to investigate the thirst-quenching ability of water-based products differing in temperature and texture (cold solids and cool liquids), flavour (flavoured and non-flavoured) and sugar content in two consecutive experiments. The first experiment tested four products of 10ml each (flavoured popsicles, flavoured beverages, ice cubes, and water). 45 healthy, thirsty participants (8 men and 37 women, mean age 25.7years SD±6.6) were randomly assigned to a flavour group representing the flavour of the popsicles and beverages: mint, lemon, raspberry. Each flavour group tasted all four products (popsicles, beverages, water, ice cubes) in four sessions on consecutive days. Participants rated their thirst and four attributes (flavour intensity, thirst-quenching, refreshing, saliva stimulating) during 3min of consumption on a 100mm VAS scale and ranked all four products on thirst-quenching ability at the end of the last session. The second experiment was performed similarly (n=61, 6 men and 55 women, mean age 23.5years SD±2.87), but used sugar-reduced popsicles to compare to the regular popsicles from the first experiment. In addition, saliva was collected before and after consumption. In the first experiment, cold solid (55.8±0.99) and flavoured (55.9±0.95) products were found to be more thirst-quenching than cool liquid (52.8±0.96) and non-flavoured products (52.8±0.96). The second experiment confirmed that saliva production increased upon consumption of these popsicles, with an increase of saliva weight from 1.7g SD ±0.15 before consumption to 2.0 SD ±0.22 after consumption. Sugar-reduced popsicles were similar in thirst-quenching ability compared to regular popsicles. Overall, cold, solid, flavoured products (such as popsicles) performed best in quenching thirst, and it appeared that sugar-reduction in these products to create healthier alternatives can be achieved without compromising on thirst-quenching abilities. These results can be useful for optimisation of products to alleviate thirst in daily life, as well as in clinical settings for patients where fluid restriction is needed.

Differences in dietary intake during chemotherapy in breast cancer patients compared to women without cancer.

PURPOSE: Breast cancer patients receiving chemotherapy often experience symptoms such as nausea, vomiting and loss of appetite that potentially affect dietary habits. This study assessed the intake of energy, macronutrients and food groups before and during chemotherapy in breast cancer patients compared with women without cancer, and determined the association between symptoms and energy and macronutrient intake. METHODS: This study included 117 newly diagnosed breast cancer patients scheduled for chemotherapy and 88 women without cancer. Habitual intake before chemotherapy was assessed with a food frequency questionnaire. Two 24-h dietary recalls were completed on random days for each participant during the whole chemotherapy treatment for patients and within 6 months after recruitment for women without cancer. Shortly, after the dietary recall, participants filled out questionnaires on symptoms. RESULTS: Before chemotherapy, habitual energy and macronutrient intake was similar for breast cancer patients and women without cancer. During chemotherapy, breast cancer patients reported a significantly lower total energy, fat, protein and alcohol intake than women without cancer, as shown by a lower intake of pastry and biscuits, cheese, legumes and meat products. A decline in subjective taste perception, appetite and hunger and experiencing a dry mouth, difficulty chewing, lack of energy and nausea were associated with a lower energy intake. CONCLUSIONS: Symptoms induced by chemotherapy are associated with lower dietary intake and manifested by a lower intake of specific food groups. To ensure an optimal dietary intake during chemotherapy, it is important to monitor nutritional status and symptom burden during chemotherapy in breast cancer patients.

[Tasty food for cancer patients: the impact of smell and taste alterations on eating behaviour]. / Smakelijk eten voor patiënten met kanker.

- This article provides an overview of smell and taste changes in cancer patients and the influence of these changes on eating behaviour and food preferences.- Taste changes seem to be more common than alterations in the sense of smell.- The changes in taste and smell are often temporary; smell and taste functions mostly return to their previous level after treatment cessation.- The type of cancer and its treatment influence changes in the sense of smell and taste, making it challenging to give general advice.- Changes in taste and smell - which can lead to modified food preferences and decreased appetite - should be taken into consideration during the treatment of cancer patients to improve the nutritional status and the effectiveness of the treatment.- This requires a personal approach, a multidisciplinary team and validated methods. Moreover, it is important to involve the environment of the patient.

Learning to (dis)like: The effect of evaluative conditioning with tastes and faces on odor valence assessed by implicit and explicit measurements.

Evaluative conditioning may be an important mechanism for learning food preferences and aversions; however, in both real life and experimental settings it has not been consistently successful. The current study aimed to gain more insight into which underlying factors may contribute to a successful outcome of olfactory evaluative conditioning. Two groups of 18 participants came in on three consecutive days, and were repeatedly exposed to four novel, neutral odors (CS) coupled to varying disliked, neutral, liked, or no stimuli (taste and/or pictures, US), following a 50% reinforcement schedule, leading to 40 odor presentations per session. Liking ratings, as well as changes in the autonomic nervous system were assessed before, during and after conditioning. We were able to induce negative, but not positive, affective changes by pairing neutral odors with tastes and pictures differing in valence. Negative as well as multimodal stimuli appear to be more potent US, since they may be considered more salient. Lastly, results of the current study imply that heart rate is responsive to changes in valence of olfactory stimuli, and perhaps even more sensitive than explicit ratings of liking.

To like or not to like: neural substrates of subjective flavor preferences.

Flavor preferences vary; what one enjoys may be disgusting to another. Previous research has indicated several brain regions associated with flavor preferences. However, by using different stimuli or different internal states to obtain differences in liking, results of these studies may be confounded. Therefore, we used one target stimulus (grapefruit juice) and fMRI to compare brain activation patterns between participants that either liked (n=16) or disliked (n=18) this stimulus. Our first aim was to investigate whether differential neural activation exists that accounts for the difference in subjective flavor preference for the target stimulus. Secondly, multivariate analysis was used to investigate whether differences in subjective liking for the target revealed similar activation patterns as differences in general liking for a sweet and bitter solution. A direct comparison of likers and dislikers of the target stimulus revealed only small differences in activations in orbitofrontal cortex (OFC) and dorsal anterior cingulate cortex (dACC). However, when using multivariate analysis, a broader activation pattern (including OFC, dACC, pregenual anterior cingulate, anterior insula and ventral striatum) was identified that discriminated likers from dislikers with an 88% success rate. Interestingly though, little overlap was found between this pattern and the pattern that discriminates liking for the sweet and bitter solutions and lesser voxels contributed to the former compared with the latter. These differences between patterns discerning innate versus learned preferences may suggest that different mechanisms are at work and highlight the importance of elucidating the neural processes of how subjective preferences are learned and acquired.

Odors: appetizing or satiating? Development of appetite during odor exposure over time.

BACKGROUND: Exposure to palatable food odors influences appetite responses, either promoting or inhibiting food intake. Possibly, food odors are appetizing after a short exposure (of circa 1-3 min), but become satiating over time (circa 10-20 min). OBJECTIVE: To investigate the effect of odor exposure on general appetite and sensory-specific appetite (SSA) over time. DESIGN: In a cross-over study, 21 unrestrained women (age: 18-45 years; BMI: 18.5-25 kg m(-2)) were exposed for 20 min to eight different odor types: five food odors, two nonfood odors and no-odor. All odors were distributed in a test room at suprathreshold levels. General appetite, SSA and salivation were measured over time. RESULTS: All food odors significantly increased general appetite and SSA, compared with the no-odor condition. The nonfood odors decreased general appetite. All effects did not change over time during odor exposure. Savory odors increased the appetite for savory foods, but decreased appetite for sweet foods, and vice versa after exposure to sweet odors. Neither food odors nor nonfood odors affected salivation. CONCLUSIONS: Palatable food odors were appetizing during and after odor exposure and did not become satiating over a 20-min period. Food odors had a large impact on SSA and a small impact on general appetite. Moreover, exposure to food odors increased the appetite for congruent foods, but decreased the appetite for incongruent foods. It may be hypothesized that, once the body is prepared for intake of a certain food with a particular macronutrient composition, it is unfavorable to consume foods that are very different from the cued food.

Gustatory and olfactory dysfunction in older adults: a national probability study.

BACKGROUND: Olfactory and gustatory functions have not been well characterized in older adults in the US. Consequently, their relationships to sociodemographic characteristics, as well as physical and mental health, were studied in a large national probability sample using brief validated tests of chemosensory function. METHODS: A five-odour identification test and taste-impregnated strips of filter paper (sweet, sour, bitter, and salty) assessed the ability to identify chemosensory stimuli. RESULTS: Severe gustatory dysfunction was more prevalent than severe olfactory dysfunction. Age, education and sex were independently associated with performance on both the olfactory and gustatory identification tasks. Higher scores were associated with female sex, higher level of education, and lower age. Odour identification scores exhibited a positive, albeit weak, correlation with BMI, and food-related odours were better identified than non-food odours. In addition, odour identification performance was also negatively associated with depressive symptoms. CONCLUSIONS: These data demonstrate a high prevalence of severe gustatory and, to a somewhat lesser extent, olfactory dysfunction in a population-based sample and demonstrate that even brief tests are capable of detecting correlations between both chemical senses and relevant health measures outside a clinical setting.

The fish is bad: Negative food odors elicit faster and more accurate reactions than other odors.

Dissociating between 'good' or 'bad' odors is arguable of crucial value for human survival, since unpleasant odors often signal danger. Therefore, negative odors demand a faster response in order to quickly avoid or move away from negative situations. We know from other sensory systems that this effect is most evident for stimuli from ecologically-relevant categories. In the olfactory system the classification of odors into the food or non-food category is of eminent importance. We therefore aimed to explore the link between odor processing speed and accuracy and odor edibility and valence by assessing response time and detection accuracy. We observed that reaction time and detection accuracy are influenced by both pleasantness and edibility. Specifically, we showed that an unpleasant food odor is detected faster and more accurately than odors of other categories. These results suggest that the olfactory system reacts faster and more accurately to ecologically-relevant stimuli that signal a potential danger.

Prevalence of smell loss in Parkinson's disease--a multicenter study.

Previous data on the prevalence of olfactory dysfunction in Parkinson's disease (PD) range from 45% to 90%. The present multicenter study aimed to provide data on the prevalence of smell loss in a large sample of PD patients from three independent populations. Olfactory sensitivity was tested in 400 patients from Australia, Germany, and The Netherlands by means of a psychophysical olfactory test, the "Sniffin' Sticks", which is comprised of 3 subtests of olfactory function. Out of the total number of patients 45.0% presented as functionally anosmic, 51.7% were hyposmic, whereas only 3.3% were normosmic. This indicates that 96.7% of PD patients present with significant olfactory loss when compared to young normosmic subjects. This figure falls to 74.5%, however, when adjusted to age-related norms. Thus, olfactory dysfunction should be considered as a reliable marker of the disease.

Is olfactory impairment in Parkinson disease related to phenotypic or genotypic characteristics?

OBJECTIVE: To evaluate the relation between olfactory impairment (OI) and other impairment domains in Parkinson disease (PD) and the characteristics of OI in patients with certain genotypic characteristics. METHODS: In 295 nondemented patients with PD and 150 controls with a similar overall age and sex distribution, olfactory function was evaluated with the identification (ID) and discrimination (DIS) tests of the Sniffin' Sticks. In patients, demographic and clinical characteristics were evaluated, and genetic analyses were performed. RESULTS: Of all patients, 61% had an impaired ID and 43% had an impaired DIS. No significant correlations >0.4 were found between olfactory scores and other demographic or clinical variables. Age and sex accounted for the 22% explained variance of the ID score regression model, whereas age, sex, and disease duration accounted for the 15% explained variance of the DIS score regression model. Parkin and DJ-1 mutation carriers (homozygous or heterozygous compound, n = 6) had normal ID scores. APOE epsilon2 or APOE epsilon4 carriers had no significantly different olfactory scores than noncarriers. The allele distribution of the alpha-synuclein (SNCA)-REP1 polymorphism in groups with an impaired or normal ID or DIS was comparable. CONCLUSIONS: Olfactory impairment (OI) in Parkinson disease (PD) may be unrelated to other impairment domains of the disease, which may indicate that olfaction is an independent feature of PD. Parkin and DJ-1 mutation carriers had normal identification scores but the number of mutation carriers is too small to draw conclusions. The APOE genotype (APOE epsilon2 or APOE epsilon4 alleles) and SNCA-REP1 polymorphism do not seem to influence olfaction in PD.