Age-Related Olfactory Decline Is Associated With Levels of Exercise and Non-exercise Physical Activities

Effect of physical activity on olfaction acuity: A systematic review

Olfaction acuity, which includes detection thresholds, discrimination and identification, appears to decline with age, obesity, and various neurological disorders. Knowing that smell influences energy intake, there is a growing interest in protecting this sense. Physical activity could be a key intervention to counteract the loss of olfaction. This systematic review aims to explore the literature on the effect of physical activity on olfaction acuity. The search strategy consisted of using index terms and keywords in MEDLINE, EMBASE, EBM Reviews - Cochrane Central Register of Controlled Trials, CINAHL, SPORTDiscus, and Web of Science search engine. Data from 17 trials involving 10,861 participants showed that physical activity improved olfaction thresholds, discrimination, identification and perceived intensity. Regular practice of physical activity seemed to have better effects on olfaction components than acute exercise. Although this review has clarified the evidence on the effects of physical activity on olfaction, better methodological consistency is needed.

Association of exercise with better olfactory performance and higher functional connectivity between the olfactory cortex and the prefrontal cortex: a resting-state fNIRS study

BACKGROUND

Olfactory deterioration is suggested to be a predictor of some neurodegenerative diseases. Recent studies indicate that physical exercise has a positive relationship with olfactory performance, and a subregion in the prefrontal cortex (PFC) may play an important role in olfactory processing. The PFC is not only related to olfactory function, but also engages in complex functions such as cognition and emotional processing.

METHODOLOGY

Our study compared the functional connectivity between the olfactory cortex and the prefrontal cortex in healthy individuals who exercised regularly and healthy persons who did not. Those who exercised more than 3 times/week for at least 30 min each time were considered the exercise group, and those who did not meet this exercise criteria were considered the non-exercise group. We also assessed their odor threshold. Participants were aged 55 years or older, and the two groups were balanced for age, sex, body mass index, and educational level.

RESULTS

We found that compared with individuals who did not exercise, exercisers had a significantly lower threshold for detecting odors. In addition, the olfactory cortex had stronger connectivity with the PFC in exercisers than in non-exercisers. More specifically, when the PFC was grouped into three subregions, namely, the ventrolateral prefrontal cortex (VLPFC), dorsolateral prefrontal cortex (DLPFC), and frontopolar cortex (FPA), Pearson correlation analysis revealed stronger connectivity between the VLPFC and the OFC, between the OFC and the FPA, and between the left and right OFC hemispheres in the exercisers. In addition, Granger causality indicated higher directional connectivity from the DLPFC to the OFC in exercisers than in non-exercisers.

CONCLUSION

Our findings indicated that the exercise group not only had better olfactory performance but also had stronger functional connectivity between the olfactory cortex and the PFC than non-exercise group.

The association between parameters of physical activity and olfactory function-the importance of frequency and moderate intensity

Introduction

Overall physical activity (PA) has been linked to decreased olfactory dysfunction and could improve olfactory function. Additionally, decreased olfactory function can contribute to reduced overall PA levels, given its association with neurodegenerative disorders. This study aims to examine the relationship between specific PA parameters (duration, frequency, intensity) and olfactory function in adults.

Methods

A total of 3,527 participants from the National Health and Nutrition Examination Survey (NHANES) 2013-2014 underwent assessments for weekly PA duration, frequency, and intensity, alongside a smell test (including odors such as chocolate, strawberry, grape, onion, smoke, natural gas, leather, and soap). Correlation analyses and binary logistic regressions using SPSS were used to evaluate associations.

Results

The total smell score exhibited small yet significant positive correlations with the duration, frequency, and volume of moderate PA (correlation coefficients ranging between 0.05 and 0.08; all p ≤ 0.05) and frequency of vigorous PA (correlation coefficient of 0.05; p < 0.05). For moderate PA, the duration, frequency, and volume were significantly and positively associated with the ability to correctly detect the smell of grapes while the frequency was significantly and positively associated with the ability to identify smoke and leather odors (odds ratios ranging from 1.01 to 1.07; p < 0.05). For vigorous PA, the frequency of PA was positively associated with the detection of grape smell (odds ratio of 1.05; p < 0.05).

Conclusion

Some parameters of an active lifestyle are associated with improved odds of accurately identifying odors by up to 7.4%. Moderate PA duration, frequency, and volume were linked to better olfactory scores, while high-intensity PA had limited associations.

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.

Effect of the rs2821557 Polymorphism of the Human Kv1.3 Gene on Olfactory Function and BMI in Different Age Groups

The sense of smell plays an important role in influencing the eating habits of individuals and consequently, their body weight, and its impairment has been associated with modified eating behaviors and malnutrition problems. The inter-individual variability of olfactory function depends on several factors, including genetic and physiological ones. In this study, we evaluated the role of the Kv1.3 channel genotype and age, as well as their mutual relationships, on the olfactory function and BMI of individuals divided into young, adult and elderly groups. We assessed olfactory performance in 112 healthy individuals (young n = 39, adult n = 36, elderly n = 37) based on their TDI olfactory score obtained through the Sniffin' Sticks test and their BMI. Participants were genotyped for the rs2821557 polymorphism of the human gene encoding Kv1.3 channels, the minor C allele of which was associated with a decreased sense of smell and higher BMIs compared to the major T allele. The results show that TT homozygous subjects obtained higher TDI olfactory scores and showed lower BMIs than CC homozygous subjects, in all age groups considered. Furthermore, the positive effect of the T allele on olfactory function and BMI decreased with increasing age. The contribution of the genetic factor is less evident with advancing age, while the importance of the age factor is compensated for by genetics. These results show that genetic and physiological factors such as age act to balance each other.

The Implications of Taste and Olfaction in Nutrition and Health

Taste and olfaction are sensory modalities that act synergistically to orchestrate the behaviors essential for survival, such as interactions with the environment, nutrient-rich food identification, and the avoidance of noxious substances [...].

Application of Artificial Neural Networks (ANN) to Elucidate the Connections among Smell, Obesity with Related Metabolic Alterations, and Eating Habit in Patients with Weight Excess

Obesity is a severe health problem linked to an increased risk of comorbidity and mortality and its etiopathogenesis includes genetic, epigenetic, microbiota composition, and environmental factors, such as dietary habits. The olfactory system plays an important role in controlling food intake and meal size, influencing body weight and energy balance. This study aims to identify the connection between olfactory function and clinical and nutritional aspects related to weight excess in a group of 68 patients with overweight or obesity. All participants underwent the evaluation of olfactory function, anthropometric data (weight, height, BMI, waist circumference), clinical data (hypertension, disglycemia, dyslipidemia, metabolic syndrome), and adherence to the Mediterranean diet (Mediterranean Diet Score). A fourth-generation artificial neural network data mining approach was used to uncover trends and subtle associations between variables. Olfactory tests showed that 65% of patients presented hyposmia. A negative correlation was found between olfactory scores and systolic blood pressure, fasting plasma glucose, and triglycerides levels, but a positive correlation was found between olfactory scores and the Mediterranean diet score. The methodology of artificial neural networks and the semantic connectivity map "Auto-Contractive Map" highlighted the underlying scheme of the connections between the variables considered. In particular, hyposmia was linked to obesity and related metabolic alterations and the male sex. The female sex was connected with normosmia, higher adherence to the Mediterranean diet, and normal values of blood pressure, lipids, and glucose levels. These results highlight an inverse correlation between olfactory skills and BMI and show that a normosmic condition, probably because of greater adherence to the Mediterranean diet, seems to protect not only from an excessive increase in body weight but also from associated pathological conditions such as hypertension and metabolic syndrome.

Olfactory training: effects of multisensory integration, attention towards odors and physical activity

Olfactory training (OT) has been shown to be of value in the treatment of olfactory dysfunction. The present study aimed to investigate whether the efficacy of OT could be modulated with multisensory integration, attention towards odors, odor complexity, or physical activity assessed with a questionnaire. One hundred healthy participants were recruited and divided into 4 groups. Except for controls (n = 26, mean age ± SD = 36 ± 15 years) all participants performed OT 4 times a day. In the "video" group (n = 26, age 39 ± 19 years) OT was performed while watching specific and congruent video sequences. In the "counter" group (n = 24, 38 ± 17 years) participants additionally counted the number of odors 1 day per week, and in the "training only" group no additional measures were taken in addition to OT (n = 24, 38 ± 20 years). "Single-molecule" odorants or "complex mixtures" were distributed randomly for training stimulation. Sniffin' sticks tests (odor identification, odor discrimination, and odor threshold), cognitive tests, and a series of scales were measured at both baseline and after 3 months of OT. The degree of physical activity was recorded with a questionnaire. Olfactory function improved in the video and counter groups after OT, especially for odor threshold and discrimination. Yet, odor complexity and the degree of physical activity had limited effects on olfactory improvement after OT. Both multisensory interaction and attention towards odors plus OT appeared to facilitate improvement of olfactory function in healthy individuals compared with OT alone and controls, which could provide new promising treatments for clinical applications.

Olfaction in (Social) Context: The Role of Social Complexity in Trajectories of Older Adults' Olfactory Abilities

Objectives: Olfaction is an important correlate of later-life health, including cognition and mortality risk. Environmental enrichment protects against olfactory decline, yet little research considers the social context as a source of sensory enrichment or stimulation. This study examines how exposure to social complexity (i.e., diversity or novelty in social networks and activities) shapes later-life olfaction. Methods: Cross-sectional and longitudinal ordered logit models analyze data from 1,447 older adults interviewed at Rounds 1 and 2 of the National Social Life, Health, and Aging Project. Results: Exposure to greater social complexity (larger social networks, greater network diversity) is associated with significantly better olfaction at baseline. Increases in network diversity and fewer network losses significantly protect against olfactory decline over time. Discussion: Findings highlight the social context as an important, yet relatively overlooked source of sensory enrichment, and underscore the need for biological applications to integrate social life dynamics into studies of health trajectories.

Machine learning approaches to predict age from accelerometer records of physical activity at biobank scale

Physical activity improves quality of life and protects against age-related diseases. With age, physical activity tends to decrease, increasing vulnerability to disease in the elderly. In the following, we trained a neural network to predict age from 115,456 one week-long 100Hz wrist accelerometer recordings from the UK Biobank (mean absolute error = 3.7±0.2 years), using a variety of data structures to capture the complexity of real-world activity. We achieved this performance by preprocessing the raw frequency data as 2,271 scalar features, 113 time series, and four images. We defined accelerated aging for a participant as being predicted older than one's actual age and identified both genetic and environmental exposure factors associated with the new phenotype. We performed a genome wide association on the accelerated aging phenotypes to estimate its heritability (h_g2 = 12.3±0.9%) and identified ten single nucleotide polymorphisms in close proximity to genes in a histone and olfactory cluster on chromosome six (e.g HIST1H1C, OR5V1). Similarly, we identified biomarkers (e.g blood pressure), clinical phenotypes (e.g chest pain), diseases (e.g hypertension), environmental (e.g smoking), and socioeconomic (e.g income and education) variables associated with accelerated aging. Physical activity-derived biological age is a complex phenotype associated with both genetic and non-genetic factors.

Olfactory Sensitivity Is Associated with Body Mass Index and Polymorphism in the Voltage-Gated Potassium Channels Kv1.3

Smell strongly contributes to food choice and its hedonistic evaluation. A reduction or loss of smell has been related to malnutrition problems, resulting in excessive weight loss or gain. Voltage-gated potassium channels Kv1.3 are widely expressed in the olfactory bulb, and contribute mainly to the value of the resting membrane potential and to the frequency of action potentials. Mutations in the Kv1.3 gene are associated with alterations in glycemic homeostasis and olfactory sensitivity. We evaluated the olfactory performance in 102 healthy subjects and its association with BMI and polymorphism in the human Kv1.3 gene. Olfactory performance, based on the olfactory threshold, discrimination and identification scores and their summed score (TDI), was measured using the “Sniffin’ Sticks” test. Subjects were genotyped for the rs2821557 polymorphism of the Kv1.3 gene, whose major allele T was associated with a super-smeller phenotype, lower plasma glucose levels and resistance to diet-induced obesity as compared with the minor allele C. Based on the Kv1.3 genotype, the TDI and I olfactory scores obtained by the subjects were the following: TT > TC > CC. Subjects who were TT homozygous or heterozygous exhibited lower BMIs and reached higher olfactory scores than those with the CC genotype. The results were sex-dependent: heterozygous females performed better than heterozygous males. These findings show an inverse relationship between olfactory function and BMI, and a significant effect of the Kv1.3 genotypes on the olfactory functions and on the BMIs of the subjects. Finally, they suggest that the sex-related differences in the olfactory function can be partially ascribed to the Kv1.3 gene’s polymorphism.

Riech- und Schmeckstörungen

Ziel der vorliegenden Übersicht ist es, einen Überblick über die Ätiologie und Diagnostik von Riech- und Schmeckstörungen zu geben. Da etwa 5 % der Allgemeinbevölkerung betroffen sind, ist es ein häufiges Krankheitsbild. Riechen und Schmecken erhielten v. a. zuletzt Aufmerksamkeit während des Aufkommens der SARS-CoV-2-Pandemie, wobei eine plötzlich aufgetretene Riech- und/oder Schmeckstörung zu den typischen Symptomen zählt. Daneben sind Riechstörungen in der Frühdiagnostik neurodegenerativer Erkrankungen von Bedeutung. Häufig zeigen Patienten mit Riechstörungen Zeichen einer Depression. Die Auswirkungen von Riech‑/Schmeckstörungen sind also umfangreich, die Therapiemöglichkeiten aktuell begrenzt. Nach einem Einblick in die Ätiologie werden Diagnostik und Therapiemöglichkeiten auf dem aktuellen Stand der Literatur erörtert. Auch zukunftsweisende Behandlungsvorstellungen, wie z. B. autologe Schleimhauttransplantationen oder olfaktorische Implantate, werden angesprochen.

A polymorphism in the human gene encoding OBPIIa affects the perceived intensity of smelled odors

Among the factors that contribute to the physiological variability of the olfactory function of individuals, an important role seems to be played by the OBPs present in the mucus that bathes the ciliated terminals of the olfactory sensory neurons, facilitating the access of odorants to the olfactory receptors. It was recently highlighted that the rs2590498 polymorphism in the odor binding-protein (OBPIIa) gene it is associated with the olfactory threshold in healthy individuals. Aim of this study was to evaluate: 1) the presence of a relationship between the threshold olfactory performance of healthy subjects and the intensity with which they perceive the smelled odorants, and 2) the effect of the rs2590498 polymorphism of the OBPIIa gene on perceived intensity. We found a positive correlation between threshold olfactory and perceived intensity, and that AA homozygous subjects reported a perceived intensity higher than heterozygous and GG homozygous subjects. By showing a positive effect of the rs2590498 polymorphism of the hOBPIIa gene on the intensity perceived, these results suggest that it allows a larger number of molecules in an odorous mixture to reach the olfactory receptors.

Relationship between Olfactory Function and BMI in Normal Weight Healthy Subjects and Patients with Overweight or Obesity

Smell plays a critical role in food choice and intake by influencing energy balance and body weight. Malnutrition problems or modified eating behaviors have been associated with olfactory impairment or loss. The obesity epidemic is a serious health problem associated with an increased risk of mortality and major physical comorbidities. The etiopathogenesis of obesity is complex and multifactorial, and one of the main factors contributing to the rapid increase in its incidence is the environment in which we live, which encourages the overconsumption of foods rich in energy, such as saturated fats and sugars. By means of the “Sniffin’ Sticks” test, we measured the olfactory threshold, discrimination and identification score (TDI score) in patients of the Obesity Center of the University Hospital (OC; n = 70) and we compared them with that of healthy normal weight controls (HC; n = 65). OC patients demonstrated a significantly lower olfactory function than HC subjects both general and specific for the ability to discriminate and identify odors, even when they were considered separately as females and males. For OC patients, a negative correlation was found between body mass index (BMI) and olfactory scores obtained by each subject, both when they were divided according to gender and when they were considered all together. Besides, normosmic OC patients showed a significantly lower BMI than hyposmic ones. A reduced sense of smell may contribute to obesity involving the responses of the cephalic phase, with a delay in the achievement of satiety and an excessive intake of high-energy foods and drinks.

[Olfactory and gustatory disorders]

Ziel der vorliegenden Übersicht ist es, einen Überblick über die Ätiologie und Diagnostik von Riech- und Schmeckstörungen zu geben. Da etwa 5 % der Allgemeinbevölkerung betroffen sind, ist es ein häufiges Krankheitsbild. Riechen und Schmecken erhielten v. a. zuletzt Aufmerksamkeit während des Aufkommens der SARS-CoV-2-Pandemie, wobei eine plötzlich aufgetretene Riech- und/oder Schmeckstörung zu den typischen Symptomen zählt. Daneben sind Riechstörungen in der Frühdiagnostik neurodegenerativer Erkrankungen von Bedeutung. Häufig zeigen Patienten mit Riechstörungen Zeichen einer Depression. Die Auswirkungen von Riech‑/Schmeckstörungen sind also umfangreich, die Therapiemöglichkeiten aktuell begrenzt. Nach einem Einblick in die Ätiologie werden Diagnostik und Therapiemöglichkeiten auf dem aktuellen Stand der Literatur erörtert. Auch zukunftsweisende Behandlungsvorstellungen, wie z. B. autologe Schleimhauttransplantationen oder olfaktorische Implantate, werden angesprochen.

G protein-coupled receptors that influence lifespan of human and animal models

Humanity has always sought to live longer and for this, multiple strategies have been tried with varying results. In this sense, G protein-coupled receptors (GPCRs) may be a good option to try to prolong our life while maintaining good health since they have a substantial participation in a wide variety of processes of human pathophysiology and are one of the main therapeutic targets. In this way, we present the analysis of a series of GPCRs whose activity has been shown to affect the lifespan of animal and human models, and in which we put a special interest in describing the molecular mechanisms involved. Our compilation of data revealed that the mechanisms most involved in the role of GPCRs in lifespan are those that mimic dietary restriction, those related to insulin signaling and the AMPK and TOR pathways, and those that alter oxidative homeostasis and severe and/or chronic inflammation. We also discuss the possibility of using agonist or antagonist drugs, depending on the beneficial or harmful effects of each GPCR, in order to prolong people's lifespan and healthspan.

Odor Identification and Regional Gray Matter Atrophy in Patients with Alzheimer's Disease, Parkinson's Disease, and the Healthy Elderly: A Cross-Sectional Structural MRI Study

Multiple associations between impaired olfactory performance and regional cortical and deep gray matter atrophy have been reported in separate studies of patients with Alzheimer’s disease (AD), Parkinson’s disease (PD), and of the healthy elderly. We aimed to evaluate such possible associations among these populations in a unified manner. Twenty AD, twenty PD patients’ and twenty healthy age- and sex-matched controls’ odor identification performance was assessed with the Lithuanian adaptation of the Sniffin’ Sticks 12 odor identification test, followed by morphometric gray matter analysis by MRI using FreeSurfer. AD patients had significantly lower cognitive performance than both PD patients and the healthy elderly, as evaluated with the Mini-Mental State Examination (MMSE). Odor identification performance was significantly worse in AD and PD patients compared with the healthy elderly; AD patients performed slightly worse than PD patients, but the difference was not statistically significant. Among patients with AD, worse odor identification performance was initially correlated with atrophy of multiple cortical and deep gray matter regions known to be involved in olfactory processing, however, only two measures—decreased thicknesses of the right medial and left lateral orbitofrontal cortices—remained significant after adjustment for possible confounders (age, MMSE score, and global cortical thickness). Among patients with PD and the healthy elderly we found no similar statistically significant correlations. Our findings support the key role of the orbitofrontal cortex in odor identification among patients with AD, and suggest that correlations between impaired odor identification performance and regional gray matter atrophy may be relatively more pronounced in AD rather than in PD.