Effects of aging on the human taste system

Association of Olfactory and Gustatory Function with Memory among Community-Dwelling Independent Older Adults

BACKGROUND

This study examined the association between memory function and reduced olfactory and gustatory function among independent community-dwelling older adults.

METHODS

This cross-sectional study included 127 older adults (65.4% women). We assessed their memory, odor, and taste identification skills. Open essence (OE) test and taste strips (TS) were used to identify hyposmia (OE test ≤6) and hypogeusia (TS test ≤8), respectively.

RESULTS

Participants with severe hyposmia had significantly poorer memory functions compared to participants without severe hyposmia. After adjusting for covariates, multivariate logistic regression models revealed a significant association between immediate recognition performance and a decreased likelihood of severe hyposmia (odds ratio=0.65; 95% confidence interval 0.47-0.90). We observed no significant association between taste function and memory.

CONCLUSION

Memory function may be associated with olfactory impairment in older adults.

Recent advances in dosage form design for the elderly: a review

INTRODUCTION

With the increase in the elderly population and the prevalence of multiple medical conditions, medication adherence, and efficacy have become crucial for the effective management of their health. The aging population faces unique challenges that need to be addressed through advancements in drug delivery systems and formulation technologies.

AREAS COVERED

The current review highlights the recent advances in dosage form design for older individuals, with consideration of their specific physiological and cognitive changes. Various dosage forms, such as modified-release tablets/capsules, chewable tablets, and transdermal patches, can be tailored to meet the specific needs of elderly patients. Advancements in drug delivery systems, such as nanotherapeutics, additive manufacturing (three-dimensional printing), and drug-food combinations, improve drug delivery and efficacy and overcome challenges, such as dysphagia and medication adherence.

EXPERT OPINION

Regulatory guidelines and considerations are crucial in ensuring the safe utilization of medications among older adults. Important factors to consider include geriatric-specific guidelines, safety considerations, labeling requirements, clinical trial considerations, and adherence and accessibility considerations.

Drug-induced olfactory and gustatory dysfunction: Analysis of FDA adverse events reporting system

OBJECTIVES

With the COVID-19 pandemic, there is growing interest and research in olfactory and gustatory dysfunction (OGD). Drug-induced dysfunction is an often overlooked etiology. While several medications include smell or taste disturbance as a side effect, there are no publications describing which medications are most frequently implicated. We aim to describe the patterns of these adverse drug reactions (ADRs) using the FDA Adverse Events Reporting System (FAERS).

METHODS

The FAERS database was queried from 2011 to 2021 for terms describing ADRs related to OGD. Terms included anosmia, hyposmia, olfactory test abnormal, olfactory nerve disorder, hallucination olfactory, parosmia, ageusia, hypogeusia, dysgeusia, and taste disorder. We identified the top reported medications associated with general smell dysfunction, general taste dysfunction, reduced smell, and altered smell.

RESULTS

From 2011 to 2021, 16,091 ADRs were reported with OGD, of which13,641 (84.8%) and 2,450 (15.2%) were associated with gustatory and olfactory reactions, respectively. Zinc products (370 reports) and fluticasone propionate (214) were most commonly associated with olfactory dysfunction, specifically reduced olfaction. Varenicline (24) and fluticasone propionate (23) were most commonly associated with altered smell. Lenalidomide (490) and sunitinib (468) were most commonly associated with gustatory dysfunction. Antineoplastic and immunomodulating medications accounted for 21.6% and 36.3% of olfactory and gustatory ADRs, respectively. Among this category, immunoglobulin drugs were the most commonly associated with OGD ADRs.

CONCLUSION

Gustatory dysfunction is more commonly reported ADR compared with olfactory dysfunction. Immunologic/rheumatologic medications are the leading culprit of reported OGD. With increasing numbers of patients presenting to otolaryngologists for OGD, it is important to consider drug-induced etiology.

LEVEL OF EVIDENCE

III.

The Influence of Nutritional Status and Sleep Quality on Gustatory Function in Older Adults

Background and Objectives: Age-related declines in taste function are common. Taste acuity can be affected by nutritional status and sleep quality. This research aims to examine the effect of nutritional status and sleep quality on gustatory function in community-dwelling older adults. Materials and Methods: This cross-sectional study included 119 community-dwelling older adults (50.4% of whom were female). The gustatory function was evaluated using four liquid taste solutions (sweet, bitter, sour, and salty) each at four different concentrations and the Mini Nutritional Assessment (MNA) and Pittsburgh Sleep Quality Index (PSQI) was applied. Additionally, anthropometric measurements were taken. Results: The mean scores on the gustatory test for the sweet, bitter, sour, and salty tastes were 2.11 ± 1.27, 2.12 ± 1.03, 2.28 ± 1.03, and 1.98 ± 1.41, respectively. There were significant differences according to gender, polypharmacy, nutritional status, and sleep quality in identifying sweet tastes (all p < 0.05). It was also found that females and participants without polypharmacy had better scores for bitter tastes. When the gustatory functions were evaluated according to BMI classification, it was determined that underweight participants had a higher sour taste score than the obese ones. Multiple regression analysis revealed that age, MNA score, PSQI score, and gender accounted for a total of 20.4% of the variance in the sweet taste score. Conclusions: Determining the relationship between taste function, nutritional status, and sleep quality in older adults is important in terms of developing new strategies for older adults who have these problems.

Sensory Capacities and Eating Behavior: Intriguing Results from a Large Cohort of Italian Individuals

Eating behavior (EB) is a complex system influenced by many factors, but an undisputed role is played by the senses. In this work, we examined the effect of the sensory capacities on EB in 1152 Italian adult individuals. After administering a questionnaire on EB and assessing sensory performance through standard audiometric, olfactory, and taste tests, the prevalence of reduced sensory capacities (RSCs) and the correlation with selected risk factors were calculated. Regression models, structural equation modelling, and conditional recursive partitioning were used to investigate the relationship between variables. Around 70% of the subjects show reduced capacities in at least one sense, with taste being the most prevalent (55.21%). Male sex, aging, and low educational level are risk factors for RSCs. The increased number of senses with reduced capacities is a predictor of diminished food adventurousness and lower liking for vegetables, fish, and alcoholic beverages, while reduced capacities (RCs) in taste is a predictor of lower liking for alcoholic beverages and sweets. Overall, in addition to providing an overall picture of RSCs in Italian samples, our study reveals the association of RSCs with EB variables. This finding could have a relevant role in influencing individuals’ dietary habits and, therefore, health status.

Taste Sensitivity of Elderly People Is Associated with Quality of Life and Inadequate Dietary Intake

Aging has been implicated in the alteration of taste acuity. Diet can affect taste sensitivity. We aimed to investigate the types of tastes altered in elderly Korean people and factors associated with taste alteration in relation to dietary intake and other factors. Elderly participants (≥65 years) and young adults were assessed to determine their recognition thresholds (RT) for sweet, salty, bitter, sour, and umami tastes. Elderly participants were further surveyed for dietary intake and non-nutritional factors. Five taste RTs were correlated with age, but only four taste RTs, except sweetness, differed between the elderly participants and young adults. Inadequate intake of iron, thiamin, folic acid, zinc, and phosphorus among the elderly participants was related to elevated taste RT levels, except for bitter taste. In both correlation and regression analyses, only salty and sour RTs were associated with energy, iron, thiamin, fiber, vitamin C, and riboflavin levels in the elderly participants. The elderly participants’ taste RTs exhibited strong associations with quality of life (QOL) but showed partial relationships with physical activity, number of medicine intakes, social gatherings, and education. Taste sensitivity may decrease with age, which is further influenced by insufficient dietary intake, especially iron and thiamin, and QOL.

The Proust Machine: What a Public Science Event Tells Us About Autobiographical Memory and the Five Senses

Our senses are constantly stimulated in our daily lives but we have only a limited understanding of how they affect our cognitive processes and, especially, our autobiographical memory. Capitalizing on a public science event, we conducted the first empirical study that aimed to compare the relative influence of the five senses on the access, temporal distribution, and phenomenological characteristics of autobiographical memories in a sample of about 400 participants. We found that the access and the phenomenological features of memories varied as a function of the type of sensory cues, but not their temporal distribution. With regard to their influence on autobiographical memory, an overlap between some senses was found, with on one hand, olfaction and taste and, on the other, vision, audition, and touch. We discuss these findings in the light of theories of perception, memory, and the self, and consider methodological implications of the sensory cuing technique in memory research, as well as clinical implications for research in psychopathological and neuropsychological populations.

Impact of the severity of dementia due to Alzheimer's disease on the gustatory sensitivity of older persons

OBJECTIVE

To evaluate the association between the severity of dementia and taste recognition abilities in older persons with Alzheimer's disease (AD).

METHODS

Anthropometric measurements were performed and body mass index was used to determine the nutritional status. The taste strips were used to test gustatory functions of the five basic tastes (sweet, salty, sour, bitter and umami).

RESULTS

A total of 30 healthy younger subjects, 30 healthy older subjects, 37 with mild stage AD and 23 with moderate stage AD were recruited. The older subjects with moderate AD showed a significant reduction of taste, less recognition of bitter and salty taste (score: 10.6 ± 2.6; 2.6 ± 0.9; 1.7 ± 1.5) when compared to older people without cognitive impairment (score: 13.3 ± 1.8; 3.4 ± 0.9; 3.2 ± 0.9), and less recognition of sweet taste (score: 2.9 ± 1.2) when compared to subjects with mild stage AD (score: 3.6 ± 0.8). Impaired recognition of salty taste was detected since the early stages of AD. Among the factors that possibly influence gustatory function, a significant correlation was detected between taste ability and age, medication intake, mini-mental state examination and the nutritional status.

CONCLUSION

The severity of dementia is directly associated with greater impairment of taste sensitivity, especially among older subjects with moderate stage disease.

Sodium and Potassium Intake in Residents of Retirement Homes

Excessive salt intake and its impact on health is a public health problem in many regions of the world. The currently estimated dietary intake of salt among free-living adults is well above the WHO recommendations. Over the years, the number of residents in retirement homes has increased. Besides this, the nutrition of elderly people may be affected by physiological changes that occur with aging. The question is whether residents of retirement homes receive a more balanced diet, or whether the trend of excessive salt consumption continues even among institutionalised elderly people. Salt and potassium intake were assessed by measuring sodium and potassium excretion over 24 h in urine collected from a sample of residents of three retirement homes in the Goriška region, Slovenia. The average salt intake was 8.3 (2.9) g/day, which was significantly higher (p < 0.001) in men than in women (10.1 (3.1) vs. 7.3 (2.2) g/day, respectively). The estimated total daily potassium intake was 2.6 (0.6) g/day in men and 2.0 (0.8) g/day in women (mean 2.2 (0.8) g/day). The ratio of sodium to potassium was 1.53 (0.48). The salt intake among residents of retirement homes in the Goriška region, especially in men, exceeds the WHO recommended daily intake of <5 g. The mean daily potassium intake was below the WHO recommendations of 3.5 g/day.

[Aging and disorders of taste and smell]

Compared with other sensory modalities, age-related alterations in taste and smell are less known and less investigated in clinical practice. In fact, the elderly with a loss of smell or taste may not always report it or be aware of it. In addition, the clinical evaluation of taste and smell by specific tests is rarely performed.

Evaluating All Potential Oral Complications of Diabetes Mellitus

Diabetes mellitus (DM) is associated with several microvascular and macrovascular complications, such as retinopathy, nephropathy, neuropathy, and cardiovascular diseases. The pathogenesis of these complications is complex, and involves metabolic and hemodynamic disturbances, including hyperglycemia, insulin resistance, dyslipidemia, hypertension, and immune dysfunction. These disturbances initiate several damaging processes, such as increased reactive oxygen species (ROS) production, inflammation, and ischemia. These processes mainly exert their damaging effect on endothelial and nerve cells, hence the susceptibility of densely vascularized and innervated sites, such as the eyes, kidneys, and nerves. Since the oral cavity is also highly vascularized and innervated, oral complications can be expected as well. The relationship between DM and oral diseases has received considerable attention in the past few decades. However, most studies only focus on periodontitis, and still approach DM from the limited perspective of elevated blood glucose levels only. In this review, we will assess other potential oral complications as well, including: dental caries, dry mouth, oral mucosal lesions, oral cancer, taste disturbances, temporomandibular disorders, burning mouth syndrome, apical periodontitis, and peri-implant diseases. Each oral complication will be briefly introduced, followed by an assessment of the literature studying epidemiological associations with DM. We will also elaborate on pathogenic mechanisms that might explain associations between DM and oral complications. To do so, we aim to expand our perspective of DM by not only considering elevated blood glucose levels, but also including literature about the other important pathogenic mechanisms, such as insulin resistance, dyslipidemia, hypertension, and immune dysfunction.

Sensory-specific impairment among older people. An investigation using both sensory thresholds and subjective measures across the five senses

Age-related sensory impairment is a slow and gradual progress, which affects multiple modalities. Two contradictory hypotheses exist about the age-related decline of sensory thresholds. The common factor theory assumes one underlying factor-which accounts for the loss of several sensory modalities simultaneously-and the specific factor theory predicts that the sensory decline is uncorrelated between different modalities. In this study, we aimed to explore whether (i) there is a common factor of sensory thresholds in older people, (ii) older people assume that sensory decline in one modality also affects other modalities, (iii) there is a relation between sensory threshold and the subjective assessment of sensory function. This was accomplished by collecting both threshold measures and self-reported ratings for smell, hearing, taste, vision, and touch function in a group of 104 older people (mean age: 67.2 years; SD: 9.85; range: 50-100 years). Results indicated that there was no common factor of sensory thresholds, hence an impairment in one modality did not necessarily imply a shortfall in other modalities. In contrast, our results suggested one or two common factor(s) for the participants' ratings. Participants who reported a diminished function in one sense tended to generalize this rating to the other senses as well. The correspondence between subjective ratings and sensory thresholds was relatively good for vision and audition, although no correlations were observed for the other domains. These findings have implications for clinicians, suggesting that subjective measures should be combined with sensory threshold measurements when evaluating sensory dysfunction. Also, these data convey a positive message for older people and their physicians by showing that loss in one sensory modality does not necessarily generalize to losses across all sensory modalities.

Influence of medications on taste and smell

Medications frequently have chemosensory side effects that can adversely affect compliance with medical treatment regimens. Hundreds of drugs have been reported to induce unpleasant tastes and/or odors as well as altered chemosensations when administered alone or in combination with other medications. Some chemosensory complaints are due to the sensory properties of the drug itself such as aversive bitter and metallic tastes. However, most chemosensory side effects of drugs are due to alterations in the transduction pathways, biochemical targets, enzymes, and transporters by the offending medications. Studies of chemosensory perception in medicated older individuals have found that taste and smell loss is greatest for those consuming the largest number of prescription drugs. There are no standard treatments for drug-induced chemosensory disorders because each drug has unique biological effects. However, there are a few treatment options to ameliorate chemosensory alterations including addition of simulated flavors to food to compensate for losses and to override offending tastes and smells.

Taste loss in the elderly: Possible implications for dietary habits

Aging may coincide with a declining gustatory function that can affect dietary intake and ultimately have negative health consequences. Taste loss is caused by physiological changes and worsened by events often associated with aging, such as polypharmacy and chronic disease. The most pronounced increase in elderly people's detection threshold has been observed for sour and bitter tastes, but their perception of salty, sweet, and umami tastes also seems to decline with age. It has often been suggested that elderly people who lose their sense of taste may eat less food or choose stronger flavors, but the literature has revealed a more complicated picture: taste loss does not appear to make elderly people prefer stronger flavors, but nutrition surveys have pointed to a greater consumption of sweet and salty foods. Real-life eating habits thus seem to be more influenced by other, social and psychological factors. Elderly gustatory function is worth investigating to identify dietary strategies that can prevent the consequences of unhealthy eating habits in the elderly. This paper discusses age-related changes in taste perception, focusing on their consequences on food preferences, and pointing to some strategies for preserving appropriate dietary habits in elderly people.

Sensory Functioning in Older Adults: Relevance for Food Preference

The world's population is aging and older adults represent the fastest growing segment of the consumer market. Changes in sensory, perceptual and cognitive function in this segment of the population have been described psychophysically, however, more is known about the young-old than the old-old or oldest-old. Only now are we exploring the potential for neuroimaging tools to probe the changes in central nervous system function related to taste and smell that are relevant to sensory perception, reward value, anticipation of and consumption of food stimuli. There is real potential for brain imaging to provide a greater understanding of older adults' consumer behavior.

Somatosensory function in old age

Sensory decline is viewed as an inevitable consequence of the ageing process. However, reports of declines have not been a consistent finding across the sensory systems. Reports from psychophysical studies indicate that the most common declines with ageing are in vision and audition and, to a lesser degree, olfaction and gustation. Findings for the somatosensory system (mechanoreception, warming and cooling thermoreception and pain) are less conclusive. Factors that contribute to individual differences in sensory ratings beyond chronological ageing include stimulus factors including stimulus type and body location, response measures and instructions, systemic disease that may affect the peripheral or central nervous system and environmental factors that may affect the skin integrity.

Age-Related Changes in Gustatory, Homeostatic, Reward, and Memory Processing of Sweet Taste in the Metabolic Syndrome: An fMRI Study

Age affects the human taste system at peripheral and central levels. Metabolic syndrome is a constellation of risk factors (e.g., abdominal obesity and hypertension) that co-occur, increase with age, and heighten risk for cardiovascular disease, diabetes, and cognitive decline. Little is known about how age, metabolic syndrome, and hunger state interact to influence how the brain processes information about taste. We investigated brain activation during the hedonic evaluation of a pleasant, nutritive stimulus (sucrose) within regions critical for taste, homeostatic energy regulation, and reward, as a function of the interactions among age, metabolic syndrome, and hunger condition. We scanned young and elderly adults, half with risk factors associated with metabolic syndrome twice: Once fasted overnight and once after a preload. Functional magnetic resonance imaging data indicated significant effects of age as well as interactive effects with metabolic syndrome and hunger condition. Age-related differences in activation were dependent on the hunger state in regions critical for homoeostatic energy regulation and basic as well as higher order sensory processing and integration. The effects of age and metabolic syndrome on activation in the insula, orbital frontal cortex, caudate, and the hypothalamus may have particularly important implications for taste processing, energy regulation, and dietary choices.

Nutrition impact symptoms, handgrip strength and nutritional risk in hospitalized patients with gastroenterological and liver diseases

OBJECTIVE

Malnutrition is common among patients with diseases of the liver and gastrointestinal tract. Nutritional intake may be negatively affected by nutrition impact symptoms (NIS). Therefore, the aims were to assess: 1) the prevalence of NIS in this group of patients and 2) the relationship between NIS and nutritional status as well as nutritional risk.

MATERIAL AND METHODS

We performed a cross-sectional study among patients with liver disease, inflammatory bowel disease, cancer or pancreatitis. Nutritional risk was assessed by the NRS-2002. Nutritional status was assessed by body mass index (BMI) and handgrip strength (HGS), which were both measured within 5 days after admission. NIS were assessed by the Eating Symptoms Questionnaire (ESQ) and the Disease-Related Appetite Questionnaire (DRAQ).

RESULTS

In total, 126 patients were included (women 39%) with a mean BMI of 24 ± 5 kg/m(2). The prevalence of low HGS was 38%, and the prevalence of those at nutritional risk was 58%. The number of NIS reported by 50% of the patients were 4 or more in the ESQ and 5 or more in the DRAQ. Patients who were both at nutritional risk and had a low HGS more frequently reported difficulties swallowing, poor appetite, feeling full after having one-fourth of the meal and food tasting bad.

CONCLUSIONS

NIS that preclude food intake are very frequent among patients with diseases of the liver and gastrointestinal tract. Specific NIS are associated with low HGS, weight loss and being at nutritional risk.

Arecoline Alters Taste Bud Cell Morphology, Reduces Body Weight, and Induces Behavioral Preference Changes in Gustatory Discrimination in C57BL/6 Mice

Arecoline, a major alkaloid in areca nuts, is involved in the pathogenesis of oral diseases. Mammalian taste buds are the structural unit for detecting taste stimuli in the oral cavity. The effects of arecoline on taste bud morphology are poorly understood. Arecoline was injected intraperitoneally (IP) into C57BL/6 mice twice daily for 1-4 weeks. After arecoline treatment, the vallate papillae were processed for electron microscopy and immunohistochemistry analysis of taste receptor proteins (T1R2, T1R3, T1R1, and T2R) and taste associated proteins (α-gustducin, PLCβ2, and SNAP25). Body weight, food intake and water consumption were recorded. A 2-bottle preference test was also performed. The results demonstrated that 1) arecoline treatment didn't change the number and size of the taste buds or taste bud cells, 2) electron microscopy revealed the change of organelles and the accumulation of autophagosomes in type II cells, 3) immunohistochemistry demonstrated a decrease of taste receptor T1R2- and T1R3-expressing cells, 4) the body weight and food intake were markedly reduced, and 5) the sweet preference behavior was reduced. We concluded that the long-term injection of arecoline alters the morphology of type II taste bud cells, retards the growth of mice, and affects discrimination competencies for sweet tastants.

The perception of materials through oral sensation

This paper presents the results of a multimodal study of oral perception conducted with a set of material samples made from metals, polymers and woods, in which both the somatosensory and taste factors were examined. A multidimensional scaling analysis coupled with subjective attribute ratings was performed to assess these factors both qualitatively and quantitatively. The perceptual somatosensory factors of warmth, hardness and roughness dominated over the basic taste factors, and roughness was observed to be a less significant sensation compared to touch-only experiments. The perceptual somatosensory ratings were compared directly with physical property data in order to assess the correlation between the perceived properties and measured physical properties. In each case, a strong correlation was observed, suggesting that physical properties may be useful in industrial design for predicting oral perception.

Taste intensity in the Beaver Dam Offspring Study

OBJECTIVES/HYPOTHESIS

To determine the distribution of the perceived intensity of salt, sweet, sour, and bitter in a large population and to investigate factors associated with perceived taste intensity.

STUDY DESIGN

Cross-sectional population.

METHODS

Subjects (n = 2,374; mean age, 48.8 years) were participants in the Beaver Dam Offspring Study examined during 2005 to 2008. Perceived taste intensity was measured using paper disks and a general labeled magnitude scale. Multiple linear regression was performed.

RESULTS

Mean intensity ratings were: salt = 27.2 (standard deviation [SD] = 18.5), sweet = 20.4 (SD = 15.0), sour = 35.7 (SD = 21.4), and bitter = 49.6 (SD = 23.3). Females and those with less than a college degree education rated tastes stronger. With adjustment for age, sex, and education, stronger perceived sour and bitter intensities were related to current smoking (sour: B = 2.8, 95% confidence interval [CI], 0.4 to 5.2; bitter: B = 2.8, 95% CI, 0.3 to 5.4) and lipid-lowering medications (sour: B = 5.1, 95% CI, 2.5 to 7.6; bitter: B = 3.2, 95% CI, 0.6 to 5.8). Alcohol consumption in the past year was related to weaker salt (B = -2.8, 95% CI, -5.3 to -0.3) and sweet intensity ratings (B = -2.3, 95% CI, -4.3 to -0.3), whereas olfactory impairment was associated with higher sweet ratings (B = 4.7, 95% CI, 1.4 to 7.9).

CONCLUSIONS

Perceived intensities were strongest for bitter and weakest for sweet. Sex and education were associated with each taste, whereas age did not demonstrate a consistent relationship. Associations with other factors differed by tastants, with current smoking and alcohol consumption being related to some tastes.

Taste loss in hospitalized multimorbid elderly subjects

BACKGROUND

Loss of the sense of taste is common among older people. Morbidities and polypharmacy may contribute to the age-related decline in gustatory function. The aims of the present study were to investigate taste perception in elderly hospitalized patients by comparing their taste recognition thresholds with those of healthy, free-living elderly individuals and to identify potential determinants of taste loss.

METHODS

The participants in this observational study were 55 elderly patients hospitalized in the acute geriatric section of the Department of Medical and Surgical Sciences at Padova University and 41 free-living individuals aged older than 65 years, randomly recruited from elderly people attending mild fitness programs at public gymnasiums in Padova. Data were collected on nutrition, health, cognitive, and functional status for all participants. Gustatory capabilities were assessed using aqueous solutions of sucrose, sodium chloride, citric acid, and quinine hydrochloride (representing sweet, salty, sour, and bitter stimuli, respectively), and taste recognition thresholds were measured in both groups.

RESULTS

In comparison with the free-living elderly subjects, those in hospital were significantly less able to recognize the taste of citric acid (P < 0.05). Low citric acid sensitivity was independently associated with advanced age (≥75 years; odds ratio [OR] 3.01, 95% confidence interval [CI] 1.01-9.82), polypharmacy (number of prescribed drugs ≥ 4; OR 2.74, 95% CI 1.01-7.72), and poor nutritional status (as assessed by Mini Nutritional Assessment score < 23.5; OR 5.08, 95% CI 1.76-14.6).

CONCLUSION

Because gustatory impairment may reduce a person's appetite and lead to inadequate dietary intake, compensatory nutritional measures, such as the use of flavor-enhanced foods, should be strongly encouraged, particularly in the hospital setting.

Pathophysiology of the anorexia of aging

PURPOSE OF REVIEW

Anorexia represents a major problem for older persons leading to weight loss, sarcopenia, functional decline, and mortality. There is increasing information on the pathophysiological mechanisms that lead to anorexia.

RECENT FINDINGS

Increasing evidence has shown the importance of gastrointestinal hormones (ghrelin, cholecystokinin, and glucagon-like peptide) and adipokines in producing the anorexia of aging. Numerous neurotransmitters have been shown to be involved in this aging anorexia, but evidence in humans is lacking.

SUMMARY

The early recognition of anorexia of aging is important to allow intervention and prevent functional deterioration in older persons. Screening tests for anorexia have been developed. New approaches to managing anorexia are being tested.

Can age-related CNS taste differences be detected as early as middle age? Evidence from fMRI

Middle-aged Americans have higher obesity rates than any other age group, yet little is known about age-related changes in central taste function during this critical time. Research on taste and aging has primarily focused on psychophysical responses, and on older adults. Central taste processing in middle-age has not been investigated. In the current study, we compared functional magnetic resonance imaging (fMRI) activation of young and middle-aged adults during hedonic evaluation of a sweet and a bitter taste. A 2 (age group) by 2 (tastant) analysis of variance (ANOVA) on fMRI activation revealed: (1) a main effect of age (young adults>middle-aged adults) in the bilateral anterior cingulate, lentiform nucleus, putamen, caudate, and right precentral gyrus; (2) a main effect of taste (sweet>bitter) in the bilateral pre- and postcentral gyri, anterior cingulate and right middle frontal gyrus; qualified by (3) an age-by-taste interaction. Further inspection of the age-by-taste interaction revealed that there was a significant effect of age (greater activation in young adults) in sensory (insula) and reward (lentiform nucleus) regions during hedonic evaluation of the sweet taste; however, there was no age effect in the bitter taste condition. Further, young adults had greater responses during hedonic evaluation of sucrose than of caffeine in several sensory and motor processing regions (pre- and postcentral gyri, insula), but there were no taste-related differences in activation in the middle-aged adults. We speculate that these results might reflect early age-related differences in central taste processing that occur prior to deficits in gustatory function observed in old age, and this might have important implications for weight changes that occur during middle-age.

Clinical pharmacology in old persons

The epidemiological transition, with a rapid increase in the proportion in the global population aged over 65 years from 11% in 2010 to 22% in 2050 and 32% in 2100, represents a challenge for public health. More and more old persons have multimorbidities and are treated with a large number of medicines. In advanced age, the pharmacokinetics and pharmacodynamics of many drugs are altered. In addition, pharmacotherapy may be complicated by difficulties with obtaining drugs or adherence and persistence with drug regimens. Safe and effective pharmacotherapy remains one of the greatest challenges in geriatric medicine. In this paper, the main principles of geriatric pharmacology are presented.

Is "processed" a four-letter word? The role of processed foods in achieving dietary guidelines and nutrient recommendations

This paper, based on the symposium "Is 'Processed' a Four-Letter Word? The Role of Processed Foods in Achieving Dietary Guidelines and Nutrient Recommendations in the U.S." describes ongoing efforts and challenges at the nutrition-food science interface and public health; addresses misinformation about processed foods by showing that processed fruits and vegetables made important dietary contributions (e.g., fiber, folate, potassium, vitamins A and C) to nutrient intake among NHANES 2003-2006 participants, that major sources of vitamins (except vitamin K) were provided by enrichment and fortification and that enrichment and fortification helped decrease the percentage of the population below the Estimated Average Requirement for vitamin A, thiamin, folate, and iron; describes how negative consumer perceptions and consumer confusion about processed foods led to the development of science-based information on food processing and technology that aligns with health objectives; and examines challenges and opportunities faced by food scientists who must balance consumer preferences, federal regulations, and issues surrounding food safety, cost, unintended consequences, and sustainability when developing healthful foods that align with dietary guidelines.

Aging profoundly delays functional recovery from gustatory nerve injury

The peripheral taste system remains plastic during adulthood. Sectioning the chorda tympani (CT) nerve, which sends sensory information from the anterior tongue to the central nervous system, causes degeneration of distal fibers and target taste buds. However, taste function is restored after about 40 days in young adult rodents. We tested whether aging impacts the reappearance of neural responses after unilateral CT nerve injury. Taste bud regeneration was minimal at day 50-65 after denervation, and most aged animals died before functional recovery could be assessed. A subset (n=3/5) of old rats exhibited normal CT responses at day 85 postsectioning, suggesting the potential for efficient recovery. The aged taste system is fairly resilient to sensory receptor loss and major functional changes in normal aging. However, injury to the taste system reveals a surprising vulnerability in old rodents. The gustatory system provides an excellent model to study mechanisms underlying delayed recovery from peripheral nerve injury. Strategies to accelerate recovery and restore normal function will be of interest, as the elderly population continues to grow.

Age-related changes in mouse taste bud morphology, hormone expression, and taste responsivity

Normal aging is a complex process that affects every organ system in the body, including the taste system. Thus, we investigated the effects of the normal aging process on taste bud morphology, function, and taste responsivity in male mice at 2, 10, and 18 months of age. The 18-month-old animals demonstrated a significant reduction in taste bud size and number of taste cells per bud compared with the 2- and 10-month-old animals. The 18-month-old animals exhibited a significant reduction of protein gene product 9.5 and sonic hedgehog immunoreactivity (taste cell markers). The number of taste cells expressing the sweet taste receptor subunit, T1R3, and the sweet taste modulating hormone, glucagon-like peptide-1, were reduced in the 18-month-old mice. Concordant with taste cell alterations, the 18-month-old animals demonstrated reduced sweet taste responsivity compared with the younger animals and the other major taste modalities (salty, sour, and bitter) remained intact.