The effects of aging on the human sense of smell and its relationship to food choice

Presbyphagia: Dysphagia in the elderly

Dysphagia has been classified as a “geriatric syndrome” and can lead to serious complications that result in a tremendous burden on population health and healthcare resources worldwide. A characteristic age-related change in swallowing is defined as “presbyphagia.” Medical imaging has shown some changes that seriously affect the safety and efficacy of swallowing. However, there is a general lack of awareness of the effects of aging on swallowing function and a belief that these changes are part of normal aging. Our review provides an overview of presbyphagia, which has been a neglected health problem for a long time. Attention and awareness of dysphagia in the elderly population should be strengthened, and targeted intervention measures should be actively implemented.

LIFEHOUSE’s Functional Nutrition Examination (Physical Exam, Anthropometrics, and Selected Biomarkers) Informs Personalized Wellness Interventions

Each individual has a unique and interacting set of genetic, lifestyle, and environmental factors that are reflected in their physical exam and laboratory biomarkers and significantly impact their experience of health. Patterns of nutrient deficiency signs and biomarker levels below health-promoting thresholds have been identified in national nutrition surveys. However, identifying these patterns remains a challenge in clinical medicine for many reasons, including clinician training and education, clinical time restraints, and the belief that these signs are both rare and recognizable only in cases of severe nutritional deficiencies. With an increased interest in prevention and limited resources for comprehensive diagnostic evaluations, a functional nutrition evaluation may augment patient-centered screening evaluations and personalized wellness programs. During LIFEHOUSE, we have documented physical exam, anthropometric, and biomarker findings that may increase the recognition of these wellness-challenging patterns in a population of 369 adult employees working in two occupational areas: administrative/sales and manufacturing/warehouse. Distinct and significant physical exam differences and constellations of biomarker abnormalities were identified. We present these patterns of physical exam findings, anthropometrics, and advanced biomarkers to assist clinicians in diagnostic and therapeutic interventions that may stem the loss of function that precedes the development of the non-communicable chronic diseases of aging.

Changes in smell and taste perception related to COVID-19 infection: a case-control study

The main aim of the present study was to psychophysically evaluate smell and taste functions in hospitalized COVID-19 patients and to compare those results with a group of healthy subjects. Another aim of the study was to assess the relationship of changes in patients’ smell and taste functions with a number of clinical parameters, symptoms, and other physiological signs as well as with severity of disease. Olfactory and gustatory functions were tested in 61 hospitalized patients positive for SARS-CoV-2 infection and in a control group of 54 healthy individuals. Overall, we found a significant impairment of olfactory and gustatory functions in COVID-19 patients compared with the control group. Indeed, about 45% of patients self-reported complaints about or loss of either olfactory or gustatory functions. These results were confirmed by psychophysical testing, which showed a significantly reduced performance in terms of intensity perception and identification ability for both taste and smell functions in COVID-19 patients. Furthermore, gustatory and olfactory impairments tended to be more evident in male patients suffering from more severe respiratory failure (i.e., pneumonia with need of respiratory support need during hospitalization).

Olfactory Sensations During Proton and Photon Radiotherapy: A Multicenter Prospective Observational Study

Purpose: Patients often report a sense of smell during radiation therapy (RT), but the details of these events are not well understood. The purpose of the study was to evaluate events of smell during photon RT and proton beam therapy (PBT).

Methods and materials: The subjects were all adult patients (≥20 years old) treated with photon RT or PBT at two centers from January 2019 to August 2020, with the exclusion of those with communication difficulties or olfactory abnormality. The presence of smell, odor type, intensity (five levels), and time period was examined prospectively using a weekly checklist.

Results: A total of 649 courses were examined in 620 patients who received photon RT (n=415) or PBT (n=205). A smell during the procedure was sensed by 51 patients (8.2%). In multivariate logistic regression analysis, nasal cavity dose (p=0.002), age (p<0.001), and photon RT (p=0.018) were identified as significant factors associated with a sense of smell. Smell occurred in only 23/515 patients (4.5%) in whom the nasal cavity was not irradiated, but in 4/19 (21.1%) and 24/86 (27.9%) with nasal cavity maximum isodose lines of 10%-50% and 60%-100%, respectively. Patients who received photon RT sensed a smell (43/415; 10.4%) more frequently than those treated with PBT (8/205; 3.9%). Of the 51 patients who sensed a smell, 32 (63%) reported a burnt smell, eight (16%) a chemical smell, two (4%) a sour smell, and nine another smell (copier machine, sweet, garbage, etc.).

Conclusions: The sense of a smell appears to be common during RT and this sensation is significantly associated with the nasal cavity dose, younger age, and photon RT.

Olfaction and Aging: A Review of the Current State of Research and Future Directions

Olfaction, the sense of smell, is characterized by a notable age-dependency such that aging individuals are more likely to have poor olfactory abilities. These impairments are considered to be mostly irreversible and as having potentially profound effects on quality of life and food behavior, as well as constituting warning signs of mortality, cognitive dysfunction, and dementia. Here, we review the current state of research on aging and olfaction, focusing on five topics which we regard to be of particular relevance for the field: nutrition and health, cognition and dementia, mortality, environment and genetics, and training-based enhancement. Under each of these headlines, we provide a state-of-the-art overview and discuss gaps in our knowledge which might be filled by further research. Understanding how olfactory abilities are diminished in aging, and how they may be alleviated or recovered, involves a set of challenging tasks for researchers in the years to come.

Gross Olfaction Before and After Laparoscopic Gastric Bypass

BACKGROUND

Obesity leads to olfaction alterations, and this can further impact food choices, appetite, and nutritional status. Bariatric procedures induce weight loss and change in taste and smell perception, but more information is needed, especially using objective olfaction tests.

METHODS

A prospective study was conducted during 6 months, with candidates to laparoscopic gastric bypass at a single institution. A preoperative nasofibroscopy and gross smell identification test (The Pocket Smell Test ®) were performed in those meeting the inclusion criteria. After 6 months, a new test was performed, and the primary objective was to determine if there was an improvement in the olfaction score. Weight loss and comorbidities improvement were also analyzed.

RESULTS

From the 30 patients with morbid obesity enrolled, 21 met the inclusion criteria and ENT evaluation. At baseline, 42.8% of patients scored 3 points, 53.3% scored 2 points, and 4.7% scored 1 point. After 6 months, there was a -81.1% of change. Seventeen patients scored 3 points (p = 0.002 vs initial) and two scored 2 points (p = 0.006 vs initial). There were no patients with less than 2 points. Weight and comorbidities had a significant improvement as well.

CONCLUSION

Laparoscopic gastric bypass improves the olfaction scores of the Pocket Smell Test in morbidly obese patients 6 months after their procedure. More complex tests can be used in candidates to bariatric surgery if low scores are detected initially. Other causes of olfaction dysfunctions should be determined if there is no improvement after weight loss.

Flavour preferences in youth versus adults: a review

OBJECTIVE

To understand the available evidence of how children and adults differ in their preferences for flavours that may be used in tobacco products.

DATA SOURCES

A total of 474 articles published between 1931 and August 2015 were retrieved through searches conducted in PubMed, EMBASE, Web of Science and PsycINFO.

STUDY SELECTION AND EXTRACTION

A 2-phase relevancy review process resulted in the identification of 59 articles and information was extracted by 2 independent reviewers.

DATA SYNTHESIS

Findings were grouped by taste and smell preferences, which are important components of overall flavour. For taste, evidence is summarised in the following categories: sweet, salty, sour, bitter, umami and fat; within each of them, findings are organised by age categories. For smell, evidence is summarised as follows: fruit/herbal/spices, tobacco and coffee and other odours. Major findings from this search indicated that sweet preference in children and adolescents was higher than in adults. Examples of preferred food-related tastes and odours for young people included cherry, candy, strawberry, orange, apple and cinnamon. Currently, all these are used to flavour cigars, cartridges for electronic cigarettes, hookah (waterpipe) and smokeless tobacco products.

CONCLUSIONS

Infants and children exhibited elevated sweet and salty preference relative to adults. Age-related changes in bitter, sour, umami and fat taste were not clear and more research would be useful. 'Sweet' food odours were highly preferred by children. Tobacco products in flavours preferred by young people may impact tobacco use and initiation, while flavours preferred by adults may impact product switching or dual use.

Olfactory disorders and quality of life--an updated review

Olfactory disorders are common and affect about one-fifth of the general population. The main causes of olfactory loss are post viral upper respiratory infection, nasal/sinus disease, and head trauma and are therefore very frequent among patients in ear, nose, and throat clinics. We have systematically reviewed the impact of quantitative, qualitative, and congenital olfactory disorders on daily life domains as well as on general quality of life and depression. From the extensive body of literature, it can be concluded that loss of the sense of smell leads to disturbances in important areas, mainly in food enjoyment, detecting harmful food and smoke, and to some extent in social situations and working life. Most patients seem to deal well and manage those restrictions. However, a smaller proportion has considerable problems and expresses a noticeable reduction in general quality of life and enhanced depression. The impact of coping strategies is discussed.

Clinical features of olfactory disorders in patients seeking medical consultation

Background

Olfactory disorders are common complaints in ENT clinics. We investigated causes and relevant features of olfactory disorders and the need for gustatory testing in patients with olfactory dysfunction.

Material/Methods

A total of 140 patients seeking medical consultations were enrolled. All patients were asked about their olfactory disorders in a structured interview of medical history and underwent thorough otolaryngologic examinations and imaging of the head.

Results

Causes of olfactory disorders were classified as: upper respiratory tract infection (URTI), sinonasal diseases (NSD), head trauma, idiopathic, endoscopic sinus surgery, congenital anosmia, and other causes. Each of the various causes of olfactory dysfunction had its own distinct clinical features. Nineteen of 54 patients whose gustation was assessed had gustatory disorders.

Conclusions

The leading causes of olfactory dysfunction were URTI, NSD, head trauma, and idiopathic causes. Gustatory disorders were fairly common in patients with olfactory dysfunction. High priority should be given to complaints of olfactory disorders.

Racial disparities in olfactory loss among older adults in the United States

BACKGROUND

Age-related olfactory loss (presbyosmia) substantially decreases quality of life, presages neurodegenerative disease, impairs nutrition, and predicts mortality. We sought to determine how race is associated with olfactory loss in older American adults in order to inform both health care and policy.

METHODS

The National Social Life, Health and Aging Project interviewed a cross-sectional nationally representative probability sample of older adults in the United States. African Americans and Hispanics were oversampled, providing power to detect disparities for these subgroups. As part of an omnibus survey of demographic, social, psychological, and biological measures, National Social Life, Health and Aging Project assessed the ability to verbally identify odors by presenting five odor pens. Multivariate ordinal logistic regression quantified racial differences in odor identification, and then tested potential confounders.

RESULTS

African Americans and Hispanics had markedly worse olfactory function (controlling for gender and age) compared with whites (p < .001), twice the magnitude of gender differences, and comparable to aging 9 years. Cognition, household assets, and education accounted for the disparity found among Hispanics but not among African Americans. Moreover, other potential confounders, such as physical or mental health, including tobacco and alcohol use, did not account for the African American health disparity, which remained significant (p = .001) after including these factors.

CONCLUSIONS

African Americans are more likely to suffer from presbyosmia, a health disparity not explained by gender, education, cognition, physical or mental health, and health behaviors. This novel health disparity may result from lifetime environmental exposures, diet, or genetic susceptibility. Dissecting the interactions among these putative mechanisms will provide insight into ameliorating this decline in critical human sensory function.

Telomere shortening impairs regeneration of the olfactory epithelium in response to injury but not under homeostatic conditions

Atrophy of the olfactory epithelium (OE) associated with impaired olfaction and dry nose represents one of the most common phenotypes of human aging. Impairment in regeneration of a functional olfactory epithelium can also occur in response to injury due to infection or nasal surgery. These complications occur more frequently in aged patients. Although age is the most unifying risk factor for atrophic changes and functional decline of the olfactory epithelium, little is known about molecular mechanisms that could influence maintenance and repair of the olfactory epithelium. Here, we analyzed the influence of telomere shortening (a basic mechanism of cellular aging) on homeostasis and regenerative reserve in response to chemical induced injury of the OE in late generation telomere knockout mice (G3 mTerc(-/-)) with short telomeres compared to wild type mice (mTerc(+/+)) with long telomeres. The study revealed no significant influence of telomere shortening on homeostatic maintenance of the OE during mouse aging. In contrast, the regenerative response to chemical induced injury of the OE was significantly impaired in G3 mTerc(-/-) mice compared to mTerc(+/+) mice. Seven days after chemical induced damage, G3 mTerc(-/-) mice exhibited significantly enlarged areas of persisting atrophy compared to mTerc(+/+) mice (p = 0.031). Telomere dysfunction was associated with impairments in cell proliferation in the regenerating epithelium. Deletion of the cell cycle inhibitor, Cdkn1a (p21) rescued defects in OE regeneration in telomere dysfunctional mice. Together, these data indicate that telomere shortening impairs the regenerative capacity of the OE by impairing cell cycle progression in a p21-dependent manner. These findings could be relevant for the impairment in OE function in elderly people.

Investigating age-related changes in taste and affects on sensory perceptions of oral nutritional supplements

BACKGROUND

sip feeds are oral nutritional supplements (ONSs) that are commonly prescribed to malnourished patients to improve their nutritional and clinical status. However, ONSs are poorly consumed and frequently wasted, with sweetness being identified as one of the factors leading to patients' dislike of ONSs.

OBJECTIVES

to investigate if age affects sweetness thresholds and if this impacts upon perceived sweetness intensity, hedonic (sweetness and overall) and ranked preference of ONS products.

DESIGN

prospective, observational.

SUBJECTS

thirty-six young adults (18-33 years) and 48 healthy older adults (63-85 years).

SETTING

Department of Food and Nutritional Sciences and the Clinical Health Sciences at the University of Reading.

METHODS

detection and recognition threshold levels, basic taste identification and 'just about right' level of sweetness were examined. Three ONSs (chocolate, vanilla, strawberry) and sucrose solutions were evaluated for hedonic sweetness, overall hedonic liking, sweetness intensity and rank preference.

RESULTS

significant differences were found in both sweetness detection and recognition thresholds (P = 0.0001) between young and older adults, with older adults more likely to incorrectly identify the taste (P = 0.0001). Despite the deterioration in sweetness sensitivity among the older adults, there were no significant differences found in sweetness intensity perceived for the ONS products presented (P > 0.05) when compared with the young adults. However, across both groups sweetness intensity was found to be correlated with overall product dislike across all flavour variants tested (R = 0.398, P = 0.0001).

CONCLUSIONS

sweetness appears to be one of many factors contributing to the dislike of ONSs. Manufacturers are encouraged to reconsider the formulations of these products so that beneficial effects of ONSs can be delivered in a more palatable and acceptable form and wastage reduced.

Designing new meals for an ageing population

Today's ageing population is an ever-increasing, highly diverse group of people wanting to live a healthy and enjoyable life. Seniors increasingly see the importance of eating healthy and delicious food in a pleasant environment in achieving happiness and well-being. Up until now, the food industry has been rather slow in transforming the wealth of available knowledge regarding the nutritional needs and sensory perception of the ageing into new food products. Based on our own and the published research of others, we discuss here how the design of new meals for an ageing population can be tackled by a consumer-led approach to food product development. After a brief overview of the underlying concepts and practices, a detailed description is given of how this approach could be used in the design of Home Meal Replacements for senior households. This description includes also a comprehensive review of the major determinants of food preference and meal choice behavior in a later age. Finally, relevant implications are derived from the work presented and future trends in the technological development of foods for the ageing highlighted.

Odour perception in relation to age, general health, anthropometry and dental state

Considering the possible role of age-related phenomena such as general health, dental health and nutrition in odour perception, their joint effect on variability in odour perception was evaluated in the present study. A total of 171 apparently healthy adults with a mean age of 66.0 years (S.D. 7.3), ranging between 53 and 86 years, living in the community took part in this study. The SENIEUR protocol was used to assess the general health status and anthropometric measures were obtained to assess the nutritional status of the persons. The sensory detection threshold for isoamyl acetate was determined to measure odour perception. Oral examinations were used to assess dental status. Those in poor general health had lower mean values for odour perception than those in good or reasonably general health. Complete denture wearers and those with partial dentures had significantly lower values for odour perception than those with only natural teeth. Odour perception correlated significantly with measures of body fat and muscle mass, indicating that a poor sense of smell is associated with low body fat and muscle area. Our results indicate that general health and dental state are important age-associated factors in odour perception. Since odour perception is an important determinant of food consumption, early detection of diminished odour perception might be an indication of physical deterioration.

Substance and tongue-region specific loss in basic taste-quality identification in elderly adults

Physiological anorexia, decreased dietary variation, and weight loss associated with poor health are common conditions in the elderly population, with changes in chemosensory perception as important contributing causes. The present study of age-related taste loss aimed to investigate the question whether this loss is generalised and unspecific, or whether it exhibits differences in relation to certain tastants and/or differences in the topographical distribution of age-related loss. Impregnated "taste strips" with four concentrations of each of the tastants sucrose, NaCl, quinine-hydrochloride, and citric acid were applied on the tip, midlateral and posteromedial tongue regions to be identified as either sweet, salty, bitter, or sour by 30 young and 26 elderly adults. The results showed more pronounced age-related loss in identification for citric acid and quinine-hydrochloride than for sucrose and NaCl at both the tip and midlateral regions, but not at the posteromedial region where both age groups performed close to chance level. These findings may have implications for food preferences, and thus, the diets of elderly people.

A speculative essay on retinoic acid regulation of neural stem cells in the developing and aging olfactory system

Circulating signals like the acidic derivative of vitamin A: retinoic acid (RA) may regulate resident stem cells in the adult nervous system, particularly in the olfactory pathway. RA is an essential factor for inducing neural stem or precursor cells that give rise to olfactory receptor neurons (ORNs) and olfactory bulb (OB) interneurons (OBINs) during embryonic development. Similar precursors in the adult brain constantly generate new ORNs and OBINs, and embryonic signaling pathways, like that via RA, may be retained or reactivated for this purpose. We have shown that RA regulates neural precursors in the embryonic and adult olfactory pathway. Moreover, RA administration after olfactory system damage stimulates an immune response and yields a more rapid recovery of olfactory-guided behavior. We suggest that olfactory integrity may be maintained by RA-mediated regulation of neurogenesis as well as local immune responses, and that aging compromises these mechanisms. The chemical senses, particularly olfaction, decline in aged individuals, and RA (via vitamin A) levels may also decline, perhaps due to changes in appetite and food intake. This synergy may result in a high prevalence of olfactory pathology in aged individuals.

Olfactory loss in aging

Olfactory loss is a common age-related complaint that may be caused by changes in the anatomy of the structures required for olfaction (for example, loss of olfactory receptor cells) or in the environment surrounding the receptor cell (for example, altered nasal mucus composition). However, aging, as well as age-related diseases and medications, may also alter the distribution, density, or function of specific receptor proteins, ion channels, or signaling molecules that affect the ability of neural elements throughout the olfactory pathway to signal and process odorant information. Although a great deal has been learned about the prevalence and nature of age-related olfactory loss, we are just beginning to explore avenues to prevent or alleviate this sensory deficit. Some studies suggest that, rather than being a necessary outcome of aging, age-associated factors such as chronic diseases, medications, and dental and sinus problems are the primary culprits in causing olfactory impairment. This idea suggests optimism in that, as we address these other age-related health issues, the prevalence of olfactory loss will lessen as well.

Odour and taste sensitivity is associated with body weight and extent of misreporting of body weight

BACKGROUND

Sensory factors are important determinants of appetite and food choices but little is known about the relationship between body weight and sensory capabilities.

OBJECTIVE

To investigate the relationship between measured body weights, misreporting of body weight and sensory capabilities.

DESIGN

In a cross-sectional sensory study, body weight was assessed by measured and self-reported body weight in healthy men (n=130) and women (n=181). Sensory capabilities were assessed as odour detection and identification, and detection for salty, sweet, sour and bitter taste.

RESULTS

Odour detection, odour identification and taste perception scores were lower in subjects with a BMI >or=28 kg/m(2) than in subjects with a BMI <28 kg/m(2) in the age group <65 years whereas in subjects >or=65 years scores were higher in subjects with a BMI >or=28 kg/m(2) than in subjects with a BMI <28 kg/m(2) (BMI*age group: P=0.015, 0.053 and 0.015, respectively). Independent of age, scores were highest in under reporters of body weight (P=0.008, 0.001 and 0.017). Differences in taste perception could be attributed to sour (P=0.015) and bitter (P=0.026) perception, but not to salty or sweet perception.

CONCLUSION

Relationship between sensory capabilities and body mass is age dependent. Compared to overweight subjects, the sensory capabilities of normal weight individuals appear to be higher (<65 years) and lower (>or=65 years). At any age, however, subjects who under reported their body weight show higher sensory capabilities.

Olfactory disorders and their consequences for quality of life

Olfactory disorders are common in the general population, but research into the consequences of these disorders has been lacking. Not until recently, when specific tools for assessing changes in quality of life due to olfactory disorders have become available, have systematic investigations been conducted. In this article we present the most important roles that olfaction plays in humans and review the scientific literature on the consequences of olfactory disorders. This review suggests that quality of life, regarding safety issues and interpersonal relations, as well as eating habits and nutritional intake are severely altered in a large proportion of patients with olfactory disorders.

Flavor enhancement as a tool for increasing pleasantness and intake of a snack product among the elderly

A yogurt-like fermented oat bran product, flavored with regular and heightened concentrations of red currant aroma, was tested in two tasting sessions (side-by-side) and, between these, in a six-day home-use (monadic testing daily, 3+3 packages of the snack) by the elderly (n=50, mean age 73.7, range 63-85 years) and the young (n=58, mean age 23.1, range 18-34 years). The subjects rated the odor and flavor intensity and pleasantness and also conducted an odor detection and identification test. In home-use, the subjects reported the quantity consumed, willingness to eat, buy or recommend the snack. The young outperformed the elderly in the olfactory test. The heightened aroma samples were initially rated as less pleasant by both age groups, but among the elderly, the ratings given to the two samples merged during exposure. For the young, the large difference in perceived odor and flavor intensities reflected marked differences in pleasantness, while the elderly were less responsive to intensity differences in their pleasantness ratings. Overall, both age groups ate less of the heightened aroma sample. Despite the impaired olfactory capabilities of the elderly, no clear indication of benefit of the enhanced flavor was found for either pleasantness or intake.

You can teach an old dog new tricks: olfaction and responses to novel foods by the elderly

It can be difficult to document effects of age-related olfactory loss on eating behavior. However, we have reported that elders, especially those with poor olfaction, were more willing to accept novel foods than were younger adults. It was also found that elderly subjects were more willing to accept foods with unpleasant odors than were young subjects. Because there is often confounding between a food's odor pleasantness and its familiarity, the purpose of this study was to separate the effects of familiarity and odor pleasantness on food acceptance by the elderly. There was no evidence for effects of age or olfactory sensitivity on food neophobia. However, elderly subjects with poor olfaction showed less reluctance to try the unpleasantly smelling foods than did other subjects. These results suggest that increased willingness to try novel foods among elderly subjects with poor olfaction in earlier work was due to decreased rejection of foods with unpleasant odors and not due to decreased food neophobia per se.

Human olfactory bulb: aging of glomeruli and mitral cells and a search for the accessory olfactory bulb

The aims of this study on the human olfactory bulb were two. First morphometry of the bulbs revealed marked declines during aging in the numbers of mitral cells and glomeruli, the bulb's principal integrative and relay elements. Numbers of glomeruli and mitral cells in each bulb of the young adult human were found to be approximately 8,000 and 40,000, respectively; these numbers declined steadily with age at an approximate rate of 10% per decade, so that in the ninth and tenth decades less than 30% of these elements remain in place. Such a marked decline with aging is suggested to underlie in part the decline in olfactory abilities (odor detection and identification) of humans with aging. In a separate study a systematic search for presence of an accessory olfactory bulb in the adult and aging bulbs was undertaken. No positive evidence for such an organized formation was found in the various regions of the adult bulbs of different age groups. The implications of these negative findings for the recent theories on human vomeronasal function and pheromonal perception are discussed.

Age-related changes in monoamines within the olfactory bulbs of the Fischer 344 male rat

In this report the olfactory bulbs (OB) were removed from 5-6 month, 15-16 month and 25-26 month male Fischer 344 rats and assayed for concentrations of monoamines and their metabolites using HPLC-EC. Concentrations of norepinephrine were significantly greater in 25-26 and 15-16 compared to the 5-6 month old rats. By contrast, the norepinephrine metabolite, 3-methoxy-4-hydroxyphenyl glycol (MHPG), was significantly lower in the 25-26 vs. the 15-16 and 5-6 month old animals. While OB concentrations of dopamine and serotonin did not differ among the three age groups, their respective metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindole-3-acetic acid (5-HIAA), were significantly reduced in the 15-16 and 25-26 month old animals compared to the 5-6 month old animals. These data show some of the age related changes which occur in the monoamines of the OB of the Fischer 344 rat. The salient bi-directional changes which are observed between norepinephrine and its metabolite, MHPG, are particularly intriguing since they reveal some of the mechanistic alterations that occur in the OB noradrenergic system, which may underlie the age related changes in olfactory related memory/recognition processes.

Sensory detection of food odour in relation to dental status, gender and age

The aim of this study was to investigate to what extent declining odour perception can be ascribed to dental status and oral hygiene habits, taking into account gender and age. Apparently healthy adults (n = 182), ranging from 53 to 93 years (mean age = 68.4) were tested. Information about oral hygiene habits (brushing teeth and cleaning dentures) and dental status was obtained by questionnaires. A validated objective procedure was used to measure sensory detection thresholds for isoamylacetate by an ascending method of limits. A significant negative correlation of odour perception with age was shown by the edentulous subjects which might reflect their wider age spread with many subjects over age 75. The evaluation of odour perception as a function of dental status shows no significant difference in odour perception between persons partial denture wearers, with natural teeth only or complete dentures. However, a tendency for lower odour perception was observed among male partial denture wearers, especially those reporting less frequent oral hygiene, which justifies further more detailed study.