The association between olfactory dysfunction and cardiovascular disease and its risk factors in middle-aged and older adults

Olfactory Impairment and the Risk of Major Adverse Cardiovascular Outcomes in Older Adults

BACKGROUND

Olfactory impairment is common in older adults and may be associated with adverse cardiovascular health; however, empirical evidence is sparse. We examined olfaction in relation to the risk of coronary heart disease (CHD), stroke, and congestive heart failure (CHF).

METHODS AND RESULTS

This study included 2537 older adults (aged 75.6±2.8 years) from the Health ABC (Health, Aging, and Body Composition) study with olfaction assessed by the 12-item Brief Smell Identification Test in 1999 to 2000, defined as poor (score ≤8), moderate (9-10), or good (11-12). The outcomes were incident CHD, stroke, and CHF. During up to a 12-year follow-up, 353 incident CHD, 258 stroke, and 477 CHF events were identified. Olfaction was statistically significantly associated with incident CHF, but not with CHD or stroke. After adjusting for demographics, risk factors, and biomarkers of CHF, the cause-specific hazard ratio (HR) of CHF was 1.32 (95% CI, 1.05-1.66) for moderate and 1.28 (95% CI, 1.01-1.64) for poor olfaction. These associations were robust in preplanned subgroup analyses by age, sex, race, and prevalent CHD/stroke. While the subgroup results were not statistically significantly different, the association of olfaction with CHF appeared to be evident among participants who reported very good to excellent health (HR, 1.47 [95% CI, 1.01-2.14] for moderate; and 1.76 [95% CI, 1.20-2.58] for poor olfaction), but not among those with fair to poor self-reported health (HR, 1.04 [95% CI, 0.64-1.70] for moderate; and 0.92 [95% CI, 0.58-1.47] for poor olfaction).

CONCLUSIONS

In community-dwelling older adults, a single olfaction test was associated with a long-term risk for incident CHF, particularly among those reporting very good to excellent health.

Pheromone-based communication influences the production of somatic extracellular vesicles in C. elegans

Extracellular vesicles (EVs) are integral to numerous biological processes, yet it is unclear how environmental factors or interactions among individuals within a population affect EV-regulated systems. In Caenorhabditis elegans, the evolutionarily conserved large EVs, known as exophers, are part of a maternal somatic tissue resource management system. Consequently, the offspring of individuals exhibiting active exopher biogenesis (exophergenesis) develop faster. Our research focuses on unraveling the complex inter-tissue and social dynamics that govern exophergenesis. We found that ascr#10, the primary male pheromone, enhances exopher production in hermaphrodites, mediated by the G-protein-coupled receptor STR-173 in ASK sensory neurons. In contrast, pheromone produced by other hermaphrodites, ascr#3, diminishes exophergenesis within the population. This process is regulated via the neuropeptides FLP-8 and FLP-21, which originate from the URX and AQR/PQR/URX neurons, respectively. Our results reveal a regulatory network that controls the production of somatic EV by the nervous system in response to social signals.

The structure and function of olfactory receptors

Olfactory receptors (ORs) form the most important chemosensory receptor family responsible for our sense of smell in the nasal olfactory epithelium. This receptor family belongs to the class A G protein-coupled receptors (GPCRs). Recent research has indicated that ORs are involved in many nonolfactory physiological processes in extranasal tissue, such as the brain, pancreas, and testes, and implies the possible role of their dysregulation in various diseases. The recently released structures of OR51E2 and consensus OR52 have also unveiled the uniqueness of ORs from other class A GPCR members. In this review, we discuss these recent developments and computational modeling efforts toward understanding the structural properties of unresolved ORs, which could guide potential future OR-targeted drug discovery.

Factors influencing olfactory function in an adult general population sample: the CHRIS study

The sense of smell allows for the assessment of the chemical composition of volatiles in our environment. Different factors are associated with reduced olfactory function, including age, sex, as well as health and lifestyle conditions. However, most studies that aimed at identifying the variables that drive olfactory function in the population suffered from methodological weaknesses in study designs and participant selection, such as the inclusion of convenience sample or only of certain age groups, or recruitment biases. We aimed to overcome these issues by investigating the Cooperative Health Research in South Tyrol (CHRIS) cohort, a population-based cohort, by using a validated odor identification test. Specifically, we hypothesized that a series of medical, demographic and lifestyle variables is associated with odor identification abilities. In addition, our goal was to provide clinicians and researchers with normative values for the Sniffin' Sticks identification set, after exclusion of individuals with impaired nasal patency. We included 6,944 participants without acute nasal obstruction and assessed several biological, social, and medical parameters. A basic model determined that age, sex, years of education, and smoking status together explained roughly 13% of the total variance in the data. We further observed that variables related to medical (positive screening for cognitive impairment and for Parkinson's disease, history of skull fracture, stage 2 hypertension) and lifestyle (alcohol abstinence) conditions had a negative effect on odor identification scores. Finally, we provide clinicians with normative values for both versions of the Sniffin' Sticks odor identification test, i.e. with 16 items and with 12 items.

Ambient Air Pollutants and Olfaction among Women 50-79 Years of Age from the Sister Study

BACKGROUND

Poor olfaction is common in older adults and may have profound adverse implications on their health. However, little is known about the potential environmental contributors to poor olfaction.

OBJECTIVE

We investigated ambient fine particulate matter [PM ≤ 2.5 μ m in aerodynamic diameter (PM 2.5 )] and nitrogen dioxide (NO 2 ) in relation to poor olfaction in middle-aged to older women.

METHODS

The Sister Study is a nationwide cohort of 50,884 women in the United States with annual average air pollutant exposures estimated based on participants' residences from enrollment (2003-2009) through 2017. This analysis was limited to 3,345 women, 50-79 years of age as of January 2018, who completed the Brief Smell Identification Test (B-SIT) in 2018-2019. Poor olfaction was defined as a B-SIT score of ≤ 9 in the primary analysis. We conducted multivariable logistic regressions, accounting for covariates and study sampling design.

RESULTS

Overall, we found little evidence for associations of air pollutants with poor olfaction. The odds ratio (OR) and 95% confidence interval (CI) of poor olfaction for each interquartile range (IQR) increment of air pollutants in 2006 were 1.03 (95% CI: 0.91, 1.17) for PM 2.5 (per 3.3   μ g / m 3 ) and 1.08 (95% CI: 0.96, 1.22) for NO 2 (per 5.7  ppb ). Results were similar in the analyses using the most recent (2017) or the cumulative average (2006-2017) air pollutant exposure data. Secondary analyses suggested potential association in certain subgroups. The OR per IQR was 1.35 (95% CI: 1.11, 1.65) for PM 2.5 among younger participants (< 54.2 years of age) and 1.87 (95% CI: 1.29, 2.71) for NO 2 among current smokers.

DISCUSSION

This study did not find convincing evidence that air pollutants have lasting detrimental effects on the sense of smell of women 50-79 years of age. The subgroup analyses are exploratory, and the findings need independent confirmation. https://doi.org/10.1289/EHP12066.

Olfactory Dysfunction as a Marker for Essential Hypertension in a Drug-Naive Adult Population: A Hospital-Based Study

BACKGROUND AND OBJECTIVE

 Essential hypertension is a leading cause of cardiovascular morbidity worldwide, but its precise etiology remains unclear. Although its prevalence is high, there is no established predictor for the condition at an early age. Recent research has suggested that olfactory function may be associated with blood pressure regulation. This study sought to explore the association between olfactory function and essential hypertension.

METHODS

 Thirty middle-aged volunteers of both sexes with essential hypertension were recruited for the study along with 30 healthy control subjects matched for age and demographic characteristics. Participants completed a demographic questionnaire and then underwent olfactory function tests to assess odor threshold and identification using the Indian Smell Identification Test (InSIT). The researchers calculated a combined threshold-identification score for both groups and performed the statistical analysis.

RESULTS

 The study group showed significant olfactory scores in comparison to the control group participants. Control group showed a significantly higher mean combined olfactory score than the study population (p = 0.03). Significant negative correlation between systolic blood pressure and olfactory function (Pearson's coefficient = -0.329, p = 0.011) and a similar significant negative correlation between diastolic blood pressure and olfactory function (Pearson's coefficient = -0.252, p = 0.052) were the other observations. Gender differences did not account for any difference in the smell sense.

CONCLUSIONS

 There may be a connection between olfactory function and blood pressure regulation in individuals with essential hypertension. However, further research is needed to better understand this association and to determine whether olfactory function could be used as a predictor or marker for hypertension.

Ct, IL-18 polymorphism, and laboratory biomarkers for predicting chemosensory dysfunctions and mortality in COVID-19

Aim

Patients with COVID-19 often experience chemosensory dysfunction. This research intends to uncover the association of RT-PCR Ct value with chemosensory dysfunctions and SpO2. This study also aims to investigate Ct, SpO2, CRP, D-dimer, and -607 IL-18 T/G polymorphism in order to find out predictors of chemosensory dysfunctions and mortality.

Materials & methods

This study included 120 COVID-19 patients, of which 54 were mild, 40 were severe and 26 were critical. CRP, D-dimer, RT-PCR, and IL-18 polymorphism were evaluated. Results & conclusion: Low Ct was associated with SpO2 dropping and chemosensory dysfunctions. IL-18 T/G polymorphism did not show an association with COVID-19 mortality; conversely, age, BMI, D-dimer and Ct values did.

Increased risk of olfactory and taste dysfunction in the United States psoriasis population

BACKGROUND

It is plausible that immunopathological processes associated with psoriasis might contribute to the occurrence of olfactory or taste dysfunction. However, the actual association was still unknown.

PURPOSE

To determine the relationship between olfactory or taste dysfunction and psoriasis.

METHODS

Two cross-sectional studies were performed by using National Health and Nutrition Examination Survey (NHANES) data. Participants with psoriasis were defined as cases and those without psoriasis were identified as controls. Taste and smell self-reported questionnaires were used to define smell/taste alterations and identification tests were used to assure the smell/taste dysfunctions. Logistic regression models with inverse probability treatment weighting (IPTW) strategies were conducted to investigated the relationship between psoriasis and olfactory or taste dysfunction.

RESULTS

Self-reported questionnaires indicated that psoriasis patients were more likely to have perceived taste alteration (IPTW-aOR = 1.43) and smell alteration (IPTW-aOR = 1.22). Identification tests revealed that psoriasis was associated with taste dysfunction (IPTW-aOR = 1.28) and olfactory dysfunction (IPTW-aOR = 1.22). Relevant findings showed that psoriasis may be significantly associated with taste or olfactory dysfunction regardless of the questionnaire data or identification examination data used.

CONCLUSION

Olfactory and taste dysfunction could be considered comorbidities in patients with psoriasis based on our observational study. Therefore, physicians should be cautious of olfaction and taste alterations among patients with psoriasis.

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 loss is a predisposing factor for depression, while olfactory enrichment is an effective treatment for depression

The loss of olfactory stimulation correlates well with at least 68 widely differing neurological disorders, including depression, and we raise the possibility that this relationship may be causal. That is, it seems possible that olfactory loss makes the brain vulnerable to expressing the symptoms of these neurological disorders, while daily olfactory enrichment may decrease the risk of expressing these symptoms. This situation resembles the cognitive reserve that is thought to protect people with Alzheimer’s neuropathology from expressing the functional deficit in memory through the cumulative effect of intellectual stimulation. These relationships also resemble the functional response of animal models of human neurological disorders to environmental enrichment, wherein the animals continue to have the induced neuropathology, but do not express the symptoms as they do in a standard environment with restricted sensorimotor stimulation.

Impact of Systemic Diseases on Olfactory Function in COVID-19 Infected Patients

Background

COVID-19 (SARS-CoV-2/2019-nCoV) is now a major public health threat to the world. Olfactory dysfunctions (ODs) are considered potential indicating symptoms and early case identification triaging for coronavirus disease 2019 (COVID-19). The most common reported comorbidities are diabetes mellitus, chronic lung disease, and cardiovascular disease. The objective of this study was to evaluate prevalence of different types of smell disorders in patients with laboratory-confirmed COVID-19 infection and impact of involved systemic diseases.

Methodology

A cross-sectional retrospective study has been done for patients with laboratory-confirmed COVID-19 infection (mild-to-moderate). The data collected from patient's files and developed online electronic questionnaire (WhatsApp) based on the patients most common and recurrent reported data including: a) symptoms of olfactory dysfunction and associated covid19 symptoms fever and headache, cough, sore throat, pneumonia, nausea, vomiting and diarrhea, arthralgia and myalgia and taste dysfunction. b) Associated systemic diseases including: diabetes, hypertension, asthma, chronic renal disease, chorionic liver disease and hypothyroidism.

Results

Of 308 patients confirmed with Covid-19 infection, (72.4%) developed OD distributed as follows; complete anosmia (57.8%), troposmia (8.4%), hyposmia (2.9%), partial anosmia (2.6%) and euosmia (0.6%). Significantly increased prevalence of diabetes, hypertension asthma in the group with olfactory dysfunction (p < 0.001), chronic liver disease (p = 0.005), and hypothyroidism (p = 0.03).

Conclusion

The development of ODs after Covid-19 infection was associated with mild disease form and lower hospitalization. In addition, it showed significant relationship with preexisting systemic diseases. Anosmia is the common modality of ODs.

Not Only COVID-19: Involvement of Multiple Chemosensory Systems in Human Diseases

Chemosensory systems are deemed marginal in human pathology. In appraising their role, we aim at suggesting a paradigm shift based on the available clinical and experimental data that will be discussed. Taste and olfaction are polymodal sensory systems, providing inputs to many brain structures that regulate crucial visceral functions, including metabolism but also endocrine, cardiovascular, respiratory, and immune systems. Moreover, other visceral chemosensory systems monitor different essential chemical parameters of “milieu intérieur,” transmitting their data to the brain areas receiving taste and olfactory inputs; hence, they participate in regulating the same vital functions. These chemosensory cells share many molecular features with olfactory or taste receptor cells, thus they may be affected by the same pathological events. In most COVID-19 patients, taste and olfaction are disturbed. This may represent only a small portion of a broadly diffuse chemosensory incapacitation. Indeed, many COVID-19 peculiar symptoms may be explained by the impairment of visceral chemosensory systems, for example, silent hypoxia, diarrhea, and the “cytokine storm”. Dysregulation of chemosensory systems may underlie the much higher mortality rate of COVID-19 Acute Respiratory Distress Syndrome (ARDS) compared to ARDSs of different origins. In chronic non-infectious diseases like hypertension, diabetes, or cancer, the impairment of taste and/or olfaction has been consistently reported. This may signal diffuse chemosensory failure, possibly worsening the prognosis of these patients. Incapacitation of one or few chemosensory systems has negligible effects on survival under ordinary life conditions but, under stress, like metabolic imbalance or COVID-19 pneumonia, the impairment of multiple chemosensory systems may lead to dire consequences during the course of the disease.

Olfactory Dysfunction: A Complication of Diabetes or a Factor That Complicates Glucose Metabolism? A Narrative Review

The present narrative review presents emerging data regarding the association between diabetes mellitus and olfactory dysfunction and discusses the role of olfactory dysfunction in glucose metabolism. We searched relevant published articles in PubMed and Google Scholar until October 2021. Main key words included “olfactory dysfunction”, “diabetes mellitus”, and “glucose metabolism”. Olfactory dysfunction has been associated with diabetes mellitus. Furthermore, it has been proposed to be a diabetic complication, given that it has been linked with microvascular complications, such as diabetic peripheral neuropathy. Interestingly, it has been suggested that olfactory dysfunction is a manifestation of central neuropathy in diabetes, a hypothesis based on the observation that diabetes, olfactory dysfunction, and cognitive decline often coexist. However, evidence is limited and inconsistent. More importantly, olfactory and endocrine systems are closely linked, and olfactory dysfunction plays a significant role in glucose metabolism and obesity. Indeed, food behaviour and energy balance are influenced by olfaction status.

A nationwide population-based study in South Korea on a relationship between height and anosmia

The relationship between anosmia and anthropometric factor has not been investigated sufficiently yet. Thus, the purpose of this study was to evaluate anthropometric risk factors of anosmia in an Asian population. Claims data of subjects over 20 years old who underwent a national health examination conducted by the Korean National Insurance Program between 2005 and 2008 were analyzed. They were followed up through the Korean National Insurance Service database. Individuals newly diagnosed with anosmia were identified after the initial health examination until the last follow-up date (December 31, 2016). The incidence of anosmia was high in females younger than 70 years old. The hazard ratio of anosmia was found to be higher in taller groups. The tallest quintile had higher risk than the shortest quintile (hazard ratio = 1.185, 95% confidence interval: 1.147–1.225) after adjusting for age, sex, BMI, income, smoking status, alcohol consumption, regular physical activity, hypertension, diabetes mellitus, and dyslipidemia. This study showed that the incidence of anosmia had a positive association with height. However, careful interpretation is needed to generalize our result because of the limitation of the study population. Further studies are needed to clarify the genetic or environmental causes of anosmia.