Characterization and Correction of Olfactory Deficits in Kidney Disease

Relationship between altered taste and smell with malnutrition among hemodialysis patients

INTRODUCTION

Alterations in taste and smell are among the most distressing symptoms experienced by haemodialysis patients. There is limited research on the relationship between these two symptoms and malnutrition in haemodialysis patients. This study aimed to investigate alterations in taste and smell in hemodialysis patients and their relationship with malnutrition.

METHODS

This cross-sectional study was carried out with 149 hemodialysis patients at the dialysis centers of three state hospitals. The Taste and Smell Dysfunction Questionnaire was used to assess the changes in patients' taste and smell, and the Prognostic Nutritional Index (PNI), as well as the Controlling Nutritional Status (CONUT) tool, were utilized to evaluate their nutritional status.

FINDINGS

A substantial percentage (45.6%) of patients reported an altered sense of smell, and 40.2% reported an altered sense of taste. The aspect of taste that was most abnormal was bitterness (46.7%); 53.0% of the patients were at moderate risk of malnutrition by PNI score, and 14.8% were categorized as malnourished by CONUT score. Malnutrition was related to dialysis vintage: a 1-year increase in vintage was associated with an increased risk of malnutrition (OR: 1.17, 95% CI 1.02-1.32, p < 0.001). Altered taste was associated with malnutrition: one-unit increase in the standard deviation of the taste subdimension score was associated with a relative risk of malnutrition (OR: 6.89, 95% CI 1.67-28.39, p < 0.001). A one-unit increase in the standard deviation of the smell subdimension was associated with relative risk of malnutrition (OR: 1.35, 95% CI 1.10-1.64, p < 0.001).

DISCUSSION

Malnutrition was found in a significantpercentage of hemodialysis patients. Altered taste and smell and the durationof dialysis treatment were significantly associated with malnutrition scores It isrecommended that healthcare professionals regularly assess alterations in tasteand smell in hemodialysis patients, as these alterations may be associated withmalnutrition, and manage these alterations accordingly.

Olfactory Dysfunctions and Chronic Kidney Disease: A Scoping Review

Chronic kidney disease (CKD) represents a significant global public health challenge. Among the various clinical complications associated with CKD, olfactory dysfunction has been identified as a factor that substantially affects the quality of life of patients. This study aims to systematically explore the prevalence, implications, and therapeutic avenues of anosmia in CKD patients. This scoping review utilized the Arksey and O'Malley framework, incorporating the Joanna Briggs Institute methodology, and followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews guidelines. The research question, formulated using the PIO framework, guided a thorough search of databases PubMed/Medline, Embase, CINAHL (Cumulative Index to Nursing and Allied Health Literature), Cochrane Library and gray literature sources. Eligibility criteria focused on studies involving CKD patients with olfactory dysfunctions. From an initial pool of 832 articles, 17 studies met the criteria, providing insights into olfactory alterations in 4,025 CKD patients. The data that have been reported, define that 55,34% of the sample experienced olfactory changes and the 8.5% experienced anosmia. This review revealed a complex interplay of factors contributing to olfactory alterations, including uremic toxins, dialysis procedures, electrolyte imbalances, and malnutrition. Findings suggested the potential recovery of olfactory function following kidney transplantation. Various assessment tools were utilized, with the University of Pennsylvania Smell Identification Test and Sniffin' Sticks emerging as the primary instruments. The observed variability in findings highlights the need for continued research to understand the mechanisms, enhance therapies, and improve quality of life for CKD patients with olfactory dysfunctions. Future studies should employ standardized methods, explore new assessment tools, and prioritize longitudinal assessments to advance our understanding and management of olfactory dysfunctions in this population.

Olfactory function in diabetes mellitus

Diabetes mellitus (DM) is an increasingly common disease in both children and adults. In addition to neuronal and/or vascular disorders, it can cause chemosensory abnormalities including olfactory deterioration. The purpose of this article is to summarize current knowledge on olfactory function in DM, highlighting the impact of co-morbidities, especially obesity, thyroid dysfunction, chronic kidney disease and COVID-19 on olfactory outcomes. Research to date mostly shows that olfactory impairment is more common in people with diabetes than in the general population. In addition, the presence of concomitant diseases is a factor increasing olfactory impairment. Such a correlation was shown for type 1 diabetes, type 2 diabetes and gestational diabetes. At the same time, not only chronic diseases, but also DM in acute conditions such as COVID-19 leads to a higher prevalence of olfactory disorders during infection. Analyzing the existing literature, it is important to be aware of the limitations of published studies. These include the small number of patients studied, the lack of uniformity in the methods used to assess the sense of smell, frequently relying on rated olfactory function only, and the simultaneous analysis of patients with different types of diabetes, often without a clear indication of diabetes type. In addition, the number of available publications is small. Certainly, further research in this area is needed. From a practical point of view decreased olfactory performance may be an indicator for central neuropathy and an indication for assessing the patient's nutritional status, examining cognitive function, especially in older patients and performing additional diagnostic tests, such as checking thyroid function, because all those changes were correlated with smell deterioration.

The prevalence and clinical significance of loss of appetite in older patients with chronic kidney disease

PURPOSE

To determine predictors of loss of appetite among older adults with chronic kidney disease (CKD).

METHODS

Demographic and clinical data, and scores of comprehensive geriatric assessment parameters of patients who were ≥ 60 years old and have CKD according to an estimated glomerular filtration rate (eGFR) of < 60 mL/min/1.73 m2 were reviewed. Loss of appetite was defined as a score of ≤ 28 in The Council on Nutrition Appetite Questionnaire. Logistic regression analysis was performed to determine the predictors of loss of appetite.

RESULTS

Of the 398 patients included, 288 (72%) were female, and the mean age was 80 ± 7. Loss of appetite was present in 233 (59%) of patients. The frequency appeared to significantly increase with a decline in eGFR to < 45 mL/min/1.73 m2 (p < 0.05). Older age, female sex, the presence of frailty, and higher scores of Insomnia Severity Index and geriatric depression scale-15 were associated with a higher risk of loss of appetite, while longer time on education, higher levels of hemoglobin, eGFR, and serum potassium, and higher scores of handgrip strength, Tinetti gait and balance test, basic and instrumental activities of daily living, and Mini-Nutritional risk Assessment (MNA) were associated with a lower risk (p < 0.05). Associations between insomnia severity and geriatric depression remained significant after adjustment for all parameters including the MNA score.

CONCLUSION

Loss of appetite is quite common in older adults with CKD and may be a sign of poor health status in older people with CKD. There is a close relationship between loss of appetite and insomnia or depressive mood.

Effect of Chronic Kidney Disease on Olfactory Function: A Case-Control Study

BACKGROUND

Olfactory function of patients with chronic kidney disease (CKD) has been found to be defective, and patients are often unaware of it. This predisposes them to malnutrition with consequence on health recovery and quality of life.

AIM

To assess the olfactory function and determine the pattern of olfactory dysfunction in patients with CKD attending the University College Hospital, Ibadan.

MATERIALS AND METHODS

This was a prospective, hospital-based case-control study of adult patients with CKD. The control group were age- and sex-matched individuals without CKD. Olfactory threshold (OT), odor discrimination (OD), and odor identification (OI) tests were carried out in participants using the "Sniffin Sticks."

RESULTS

There were 100 patients with CKD and 100 healthy controls, age ranges between 19 to 86 years (mean ± SD = 46.3 ± 13.9 years) and 20 to 85 years (mean ± SD = 43.4 ± 14.9 years), respectively. There was no statistically significant difference between cases and control gender distribution (P = .57). The mean olfactory scores were significantly lower among the cases than control, OI 11.2 ± 2.3 and 13.1 ± 1.2 (P < .001), OD 8.5 ± 2.4 and 10.9 ± 1.5 (P < .001), OT 6.4 ± 2.5 and 9.6 ± 1.9 (P < .001), and threshold discrimination and identification 26.0 ± 5.7 and 33.6 ± 3.3 (P < .001), respectively. Prevalent olfactory dysfunction among patients with CKD was 77% (hyposmia 72%, anosmia 5%), and the control was 16% (all hyposmia; P < .001).

CONCLUSION

There was high prevalence of olfactory dysfunction among patients with CKD, and the affectation is more at the central olfactory pathway.

Comparison between olfactory training and curcumin therapy in improving olfactory dysfunction in patients with chronic kidney disease

Objective

Olfactory dysfunction can be seen in chronic kidney disease (CKD) patients. We aimed to investigate the effects of olfactory training and curcumin on olfactory dysfunction in CKD patients and compare their impact with a placebo.

Methods

We conducted a double-blind, randomized, placebo-controlled trial in CKD patients, 2021-2022. We enrolled 60 participants in our study into three groups (curcumin, training, and control). Participants were randomized into trials and control groups and assessed using the Iran-smell identification test (Iran-SIT), a questionnaire of olfactory disorders (QOD), and a self-assessment tool. P-value < 0.05 was considered statistically significant.

Results

We gathered 58 participants (mean age of 56.1 ± 2.5, 56.9% men). All the tests showed that curcumin improved olfactory function after the trial, though it was significant in QOD (17.5 ± 11.8 vs. 13.1 ± 9.7, p = 0.045) and self-assessment results (8.5 ± 3.1 vs. 9.5 ± 4.0, p = 0.047). Moreover, compared to baseline, training patients experienced an increase in their olfactory function in Iran-SIT (15.3 ± 4.9 vs. 18.8 ± 2.7, p = 0.001), QOD (19.0 ± 10.4 vs. 12.2 ± 9.9, p = 0.003), and self-assessment tools (6.8 ± 1.8 vs. 8.2 ± 3.1, p = 0.027). In contrast, the olfactory function was unchanged in control in all the tests (p > 0.05). Also, the improved change of Iran-SIT and QOD scores during the trial was more significant in training compared to the curcumin group (p < 0.002).

Conclusion

The findings of this study indicate that olfactory training, even more than curcumin, can improve olfactory function in CKD patients. This information may help manage olfactory dysfunction in the CKD population.

Bloody olfaction? Confounding associations of sex and age on the influence of blood parameters and body weight on odor identification performance in healthy adults

Olfactory function and nutrition are closely related and may influence each other via metabolic parameters. However, the relationship between nutritional blood parameters and olfactory performance is still unclear. Inconclusive findings exist for specific blood parameters. In this extensive analysis, we examined the relationship between olfactory performance, measured with MONEX-40, as well as intensity and pleasantness ratings with 38 metabolic blood parameters, age, sex, and the anthropometric measurements body mass index (BMI) and body fat percentage (BFP). Therefore, we included data of 418 healthy, well-phenotyped Caucasians of the Enable cohort. We replicated age-dependent olfactory identification scores (p < 0.001) and found slight evidence for a body fat dependence measured with BFP (BF₁₀ = 10.466). We further identified a sex difference only in middle-aged adults (p < 0.001) that could be explained by environmental factors. Several blood parameters correlated significantly with the MONEX-40 score (p < 0.05 - p < 0.001). However, these effects diminished after adjusting for sex and age (p > 0.9) that were identified as confounders. The same applies for BFP. In addition, no parameters were identified to correlate significantly with perceived olfactory intensity or pleasantness score if controlled for sex and age (p > 0.08). Our results suggest that metabolic blood parameters are not related to olfactory identification performance in a relevant manner and highlight the importance of controlling for sex and age in chemosensory research.

Validity and Reliability Study of the Turkish Adaptation of Taste and Smell Dysfunction Questionnaire in Hemodialysis Patients

AIM

This study was conducted to assess the validity and reliability of the Turkish adaptation of the Taste and Smell Dysfunction Questionnaire (TSDQ) in hemodialysis patients.

MATERIALS AND METHODS

This study involves 125 hemodialysis patients. Research data were collected using the Descriptive Characteristics Form for Hemodialysis Patients, the TSDQ, and the Questionnaire for the Assessment of Self-Reported Olfactory Functioning and Olfaction-Related Quality of Life. In addition, the questionnaire's language and content validity, construct validity, and reliability were evaluated.

RESULTS

With regard to content validity, a high degree of agreement was determined between expert opinions on the questionnaire items (CGI = 0.96). Exploratory factor analysis revealed that the questionnaire has a two-factor structure explaining 79.33% of the total variance. The confirmatory factor analysis demonstrated that the model is within acceptable fit index limits with factor loads between 0.692 and 0.964. The Cronbach's alpha reliability coefficients of the scale and its two sub-dimensions are 0.928, 0.968, and 0.782, respectively.

CONCLUSION

The TSDQ is a valid and reliable tool for evaluating taste and smell changes in hemodialysis patients.

A Novel Approach for Managing Protein-Energy Wasting in People With Kidney Failure Undergoing Maintenance Hemodialysis: Rationale and Call for Trials

Protein-energy wasting (PEW) is a unique presentation of protein-energy malnutrition in people with kidney disease that is characterized by body protein catabolism exceeding anabolism. PEW is especially common in patients undergoing maintenance hemodialysis (HD) treatment. Dietary guidelines for managing PEW in HD patients primarily focus on protein adequacy and typically promote the intake of animal-based protein foods. Although intake of protein and essential amino acids is important for protein synthesis, the emphasis on protein adequacy largely fails to address-and may actually exacerbate-many of the root causes of PEW. This perspective examines the dietary determinants of PEW in people undergoing HD treatment, with an emphasis on upstream disease-related factors that reduce dietary protein utilization and impair dietary intakes. From this, we present a theoretical diet model for managing PEW that includes etiology-based dietary strategies to address barriers to intake and treat disease-related factors, as well as supportive dietary strategies to promote adequate energy and protein intakes. Given the complexity of diet-disease interactions in the pathogenesis of PEW, and its ongoing burden in HD patients, interventional trials are urgently needed to evaluate alternative diet therapy approaches for PEW in this population.

Efficacy and Safety of Saline Nasal Irrigation Plus Theophylline for Treatment of COVID-19-Related Olfactory Dysfunction: The SCENT2 Phase 2 Randomized Clinical Trial

Importance

Recent studies suggest that theophylline added to saline nasal irrigation (SNI) can be an effective treatment for postviral olfactory dysfunction (OD), a growing public health concern during the COVID-19 pandemic.

Objective

To evaluate the efficacy and safety of theophylline added to SNI compared with placebo for COVID-19-related OD.

Design, Setting, and Participants

This triple-blinded, placebo-controlled, phase 2 randomized clinical trial was conducted virtually between March 15 and August 31, 2021. Adults residing in Missouri or Illinois were recruited during this time period if they had OD persisting for 3 to 12 months following suspected COVID-19 infection. Data analysis was conducted from October to December 2021.

Interventions

Saline sinus rinse kits and bottles of identical-appearing capsules with either 400 mg of theophylline (treatment) or 500 mg of lactose powder (control) were mailed to consenting study participants. Participants were instructed to dissolve the capsule contents into the saline rinse and use the solution to irrigate their nasal cavities in the morning and at night for 6 weeks.

Main Outcomes and Measures

The primary outcome was the difference in the rate of responders between the treatment and the control arms, defined as a response of at least slightly better improvement in the Clinical Global Impression-Improvement scale posttreatment. Secondary outcome measures included changes in the University of Pennsylvania Smell Identification Test (UPSIT), the Questionnaire for Olfactory Disorders, the 36-Item Short Form Health Survey on general health, and COVID-19-related questions.

Results

A total of 51 participants were enrolled in the study; the mean (SD) age was 46.0 (13.1) years, and 36 (71%) participants were women. Participants were randomized to SNI with theophylline (n = 26) or to SNI with placebo (n = 25). Forty-five participants completed the study. At the end of treatment, 13 (59%) participants in the theophylline arm reported at least slight improvement in the Clinical Global Impression-Improvement scale (responders) compared with 10 (43%) in the placebo arm (absolute difference, 15.6%; 95% CI, -13.2% to 44.5%). The median difference for the UPSIT change between baseline and 6 weeks was 3.0 (95% CI, -1.0 to 7.0) for participants in the theophylline arm and 0.0 (95% CI, -2.0 to 6.0) for participants in the placebo arm. Mixed-model analysis revealed that the change in UPSIT scores through study assessments was not statistically significantly different between the 2 study arms. Eleven (50%) participants in the theophylline arm and 6 (26%) in the placebo arm had a change of 4 or more points in UPSIT scores from baseline to 6 weeks. The difference in the rate of responders as measured by the UPSIT was 24% (95% CI, -4% to 52%) in favor of theophylline.

Conclusions and Relevance

This randomized clinical trial suggests that the clinical benefit of theophylline nasal irrigations on olfaction in participants with COVID-19-related OD is inconclusive, though suggested by subjective assessments. Larger studies are warranted to investigate the efficacy of this treatment more fully.

Trial Registration

ClinicalTrials.gov Identifier: NCT04789499.

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.

International consensus statement on allergy and rhinology: Olfaction

BACKGROUND

The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we have gathered experts from around the world to produce this International Consensus on Allergy and Rhinology: Olfaction (ICAR:O).

METHODS

Using previously described methodology, specific topics were developed relating to olfaction. Each topic was assigned a literature review, evidence-based review, or evidence-based review with recommendations format as dictated by available evidence and scope within the ICAR:O document. Following iterative reviews of each topic, the ICAR:O document was integrated and reviewed by all authors for final consensus.

RESULTS

The ICAR:O document reviews nearly 100 separate topics within the realm of olfaction, including diagnosis, epidemiology, disease burden, diagnosis, testing, etiology, treatment, and associated pathologies.

CONCLUSION

This critical review of the existing clinical olfaction literature provides much needed insight and clarity into the evaluation, diagnosis, and treatment of patients with olfactory dysfunction, while also clearly delineating gaps in our knowledge and evidence base that we should investigate further.

Olfaction and kidney function in community-dwelling older adults

Background

In older adults, kidney function declines with age. People with advanced kidney diseases may have poor olfaction. However, it is unclear whether poor olfaction is a marker for declining renal function or future risk of chronic kidney disease (CKD). We therefore investigated olfaction in relation to kidney function and risk of CKD.

Methods

These secondary data analyses were limited to participants of the year 3 clinical visit of the Health Aging and Body Composition Study. The analytic sample size varied between 1427 to 2531, depending on participant eligibility and data availability for each analysis. Olfaction was tested using the Brief Smell Identification Test (B-SIT), defined as anosmia (score≤6), hyposmia (7–8), moderate (9–10), and good function (10–11) at baseline. We estimated glomerular filter rate (eGFR) at baseline and seven years later using the CKD-EPI creatinine-cystatin C equation, and defined incident CKD as eGFR<60 ml/min/1.73m2 and eGFR decline ≥1 ml/min/1.73m2/year. Further, we identified CKD hospitalization events from hospitalization and death records. We used inverse probability weighting and weighted multivariable regressions to account for censoring in the prospective analyses and used absolute risk regression to account for competing risk of death.

Results

At baseline, compared to participants with good olfaction, the multivariable-adjusted mean eGFR was 3.00 ml/min/1.73m2 lower (95% confidence interval (CI): -5.25, -0.75) for those with anosmia and 1.87 lower (95% CI: -3.94, 0.21) for those with hyposmia with a P for linear trend < 0.001. Those with anosmia at baseline was had a significantly lower eGFR seven years later (-5.31, 95% CI: -8.58, -2.04, P for trend = 0.002), but the association was attenuated after further accounting for baseline eGFR (-2.37, 95%CI: -4.91, 0.16, P for linear trend = 0.147). Olfactory function was not associated with incident CKD or CKD hospitalization.

Conclusion

In older adults > age 70 years, poor olfaction is associated with lower kidney function, but not future CKD risk. These associations should be further investigated in relatively younger population.

Neuroimmunoendocrine Link Between Chronic Kidney Disease and Olfactory Deficits

Chronic kidney disease (CKD) is a multifactorial pathology that progressively leads to the deterioration of metabolic functions and results from deficient glomerular filtration and electrolyte imbalance. Its economic impact on public health is challenging. Mexico has a high prevalence of CKD that is strongly associated with some of the most common metabolic disorders like diabetes and hypertension. The gradual loss of kidney functions provokes an inflammatory state and endocrine alterations affecting several systems. High serum levels of prolactin have been associated with CKD progression, inflammation, and olfactory function. Also, the nutritional status is altered due to impaired renal function. The decrease in calorie and protein intake is often accompanied by malnutrition, which can be severe at advanced stages of the disease. Nutrition and olfactory functioning are closely interconnected, and CKD patients often complain of olfactory deficits, which ultimately can lead to deficient food intake. CKD patients present a wide range of deficits in olfaction like odor discrimination, identification, and detection threshold. The chronic inflammatory status in CKD damages the olfactory epithelium leading to deficiencies in the chemical detection of odor molecules. Additionally, the decline in cognitive functioning impairs the capacity of odor differentiation. It is not clear whether peritoneal dialysis and hemodialysis improve the olfactory deficits, but renal transplants have a strong positive effect. In the present review, we discuss whether the olfactory deficiencies caused by CKD are the result of the induced inflammatory state, the hyperprolactinemia, or a combination of both.

Therapies for Olfactory Dysfunction — an Update

Purpose of Review

Olfactory dysfunction is a prevalent condition affecting 5–15% of the general population, with significant impact on quality of life. This review summarizes the most recent and relevant literature in the treatment of olfactory dysfunction.

Recent Findings

Current evidence supports the short-term use of topical corticosteroids and systemic therapy. These treatments may occur in conjunction with olfactory training, which is well supported by the literature. While there are several additional treatments currently under investigation, meaningful conclusions are not yet able to be made regarding their efficacy.

Summary

The treatment of olfactory dysfunction is targeted at the suspected etiology when possible. After normal aging, chronic rhinosinusitis, post-infectious sequelae including as a result SARS-CoV-2 infection (COVID-19), and head trauma are the most common causes. Current evidence supports the short-term use of topical corticosteroids and systemic therapy. Several additional treatments are under investigation but recommendations for their use cannot currently be made.

Graphical abstract

The association between olfactory and gustatory dysfunction and chronic kidney disease

BACKGROUND

Olfactory and gustatory changes may contribute to poor appetite and food aversion in chronic kidney disease (CKD), though the prevalence of olfactory and gustatory dysfunction is not known in the CKD population.

METHODS

We conducted a cross-sectional study among 3527 US adults aged ≥40 years old in the National Health and Nutrition Examination Survey (NHANES) between 2013 and 2014. We measured the prevalence of olfactory and gustatory dysfunction among patients with CKD defined as eGFR < 60 ml/min/1.73m² using the "scratch and sniff" NHANES Pocket Smell Test and quinine whole-mouth test. We also examined the association between CKD and olfactory/gustatory dysfunction, and nutritional markers.

RESULTS

The prevalence of olfactory dysfunction was 30% among CKD and 15% among non-CKD (p < 0.001). The prevalence of gustatory dysfunction was 13% among CKD and 17% among non-CKD (p = 0.10). After adjusting for confounders, CKD was significantly associated with olfactory dysfunction (OR = 1.47, 95% CI [1.07, 2.01]; p = 0.02) but not gustatory dysfunction (OR = 1.76, 95%CI [0.99, 3.11]; p = 0.05). Among the CKD population, the odds of olfactory dysfunction was 72% higher for every 10 kg decrease in grip strength (OR = 1.72, 95% CI [1.39, 2.13]; adjusted p = 0.005).

CONCLUSION

CKD was associated with higher odds of olfactory but not gustatory dysfunction. Olfactory dysfunction was associated with lower grip strength among those with CKD. Screening and early intervening on olfactory dysfunction among CKD may preserve muscle strength and improve nutritional status in this vulnerable population.

Time on previous renal replacement therapy is associated with worse outcomes of COVID-19 in a regional cohort of kidney transplant and dialysis patients

ABSTRACT

Chronic renal replacement therapy by either a kidney transplant (KTX) or hemodialysis (HD) predisposes patients to an increased risk for adverse outcomes of COVID-19. However, details on this interaction remain incomplete. To provide further characterization, we undertook a retrospective observational cohort analysis of the majority of the hemodialysis and renal transplant population affected by the first regional outbreak of severe acute respiratory distress syndrome coronavirus 2 (SARS-CoV-2) in Germany. In a region of 250,000 inhabitants we identified a total of 21 cases with SARS-CoV-2 among 100 KTX and 260 HD patients, that is, 7 KTX with COVID-19, 14 HD with COVID-19, and 3 HD with asymptomatic carrier status. As a first observation, KTX recipients exhibited trends for a higher mortality (43 vs 18%) and a higher proportion of acute respiratory distress syndrome (ARDS) (57 vs 27%) when compared to their HD counterparts. As a novel finding, development of ARDS was significantly associated with the time spent on previous renal replacement therapy (RRT), defined as the composite of dialysis time and time on the transplant (non-ARDS 4.3 vs ARDS 10.6 years, P = .016). Multivariate logistic regression analysis showed an OR of 1.7 per year of RRT. The association remained robust when analysis was confined to KTX patients (5.1 vs 13.2 years, P = .002) or when correlating the time spent on a renal transplant alone (P = .038). Similarly, longer RRT correlated with death vs survival (P = .0002). In conclusion our data suggest renal replacement vintage as a novel risk factor for COVID-19-associated ARDS and death. The findings should be validated by larger cohorts.

Impact of renal replacement therapies on olfactory ability: results of a cross-sectional case control study

Introduction

Several studies have suggested that chronic kidney disease (CKD) may be associated with olfactory impairment. However, to date, the impact of renal replacement therapies has only been partly defined.

Methods

We tested the olfactory function of 235 participants [50 kidney transplant recipients (KT), 49 hemodialyzed patients (HD), 30 peritoneal dialysis patients (PD), 51 patients with CKD not on dialysis (ND-CKD) and 55 healthy subjects (HS)] by the Sniffin’ Sticks test (Burghardt®, Wedel, Germany), including the sub-tests for the determination of odor threshold (T), odor discrimination (D), odor identification (I). Each subtest result was then summed up to a composite score, known as the TDI score. The Sino-Nasal Outcome Test-22 (SNOT22), Montreal Cognitive Assessment (MoCA) test and olfactory function Visual Analogue Scale (ofVAS) were also performed.

Results

The mean TDI score was significantly lower (and consistent with hyposmia), in HD, PD and ND-CKD compared to HS and KT (ANOVA p < 0.001). Similar results were observed in the I and D tests, and with the T score, though with regard to the latter, only in PD and ND-CKD patients. Multiple comparisons among groups demonstrated no significant differences between KT and HS. After adjustments for confounding factors, a significant linear association was found between both urea (β − 0.03, p < 0.003) and eGFR (β 0.08, p < 0.001) with TDI score. No significant association was observed between the TDI score and the ofVAS score (p = 0.293).

Conclusions

Olfactory impairment affects a large number of CKD patients in the pre-dialysis phase as well as those on dialysis. Kidney transplantation may reverse this condition with a possible positive impact on the quality of life and social behaviors/relationships.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40620-021-00983-6.

Construction and Validation of Predictive Model to Identify Critical Genes Associated with Advanced Kidney Disease

Background

Chronic kidney disease (CKD) is characterized by progressive renal function loss, which may finally lead to end-stage renal disease (ESRD). The study is aimed at identifying crucial genes related to CKD progressive and constructing a disease prediction model to investigate risk factors.

Methods

GSE97709 and GSE37171 datasets were downloaded from the GEO database including peripheral blood samples from subjects with CKD, ESRD, and healthy controls. Differential expressed genes (DEGs) were identified and functional enrichment analysis. Machine learning algorithm-based prediction model was constructed to identify crucial functional feature genes related to ESRD.

Results

A total of 76 DEGs were screened from CDK vs. normal samples while 10,114 DEGs were identified from ESRD vs. CDK samples. For numerous genes related to ESRD, several GO biological terms and 141 signaling pathways were identified including markedly upregulated olfactory transduction and downregulated platelet activation pathway. The DEGs were clustering in three modules according to WGCNA access, namely, ME1, ME2, and ME3. By construction of the XGBoost model and dataset validation, we screened cohorts of genes associated with progressive CKD, such as FZD10, FOXD4, and FAM215A. FZD10 represented the highest score (F score = 21) in predictive model.

Conclusion

Our results demonstrated that FZD10, FOXD4, PPP3R1, and UCP2 might be critical genes in CKD progression.

Systematic evaluation of olfaction in patients with hereditary cystic kidney diseases/renal ciliopathies

BACKGROUND

Hereditary cystic kidney diseases such as nephronophthisis, polycystic kidney disease and Bardet-Biedl syndrome (BBS) are caused by a dysfunction of primary cilia. Cilia are involved in a variety of cellular functions and perceptions, with one of them being the sense of smell. Hyposmia is a typical feature found in patients with BBS. However, reports of olfactory dysfunction in other cystic kidney diseases are sparse. Here we provide a systematic survey on olfaction in a large cohort of patients displaying genetically determined renal ciliopathies.

METHODS

We performed a match-controlled systematic olfactory evaluation in a group of 75 patients with a defined genetic background using age adapted and validated odour identification tests.

RESULTS

Test results revealed a significant olfactory deficit in patients carrying TMEM67 variants (n=4), while all other genetic disorders causing nephronophthisis (n=25) or polycystic kidney disease (n=18) were not associated with an impaired sense of smell. Also in patients with BBS, olfactory performance was depending on the underlying molecular defect. While defects in the BBS1 gene (n=9) had no impact on the sense of smell, all other BBS gene disorders (n=19) were associated with significant hyposmia. Noteworthy, there was no correlation of the olfactory deficit with the level of renal impairment.

CONCLUSION

Hyposmia is a part of the clinical spectrum of BBS and of other renal ciliopathies. Depending on the genetic background, clinicians should be aware of this subtle and so far underappreciated symptom when clinically assessing patients with BBS or TMEM67 gene variants.

Prevalence of Taste Changes and Association with Other Nutrition-Related Symptoms in End-Stage Kidney Disease Patients

OBJECTIVES

Gastrointestinal symptoms are common in end-stage kidney disease (ESKD) and have been associated with reduced health-related quality of life and malnutrition. The aim of this study is to describe the prevalence of taste changes in an ESKD population and to evaluate whether taste changes are associated with the presence or severity of other nutrition-related symptoms and malnutrition.

METHODS

We conducted a retrospective audit of people with ESKD on conservative, nondialysis management or renal replacement therapy who had completed a taste change assessment. Taste change was assessed on a Likert scale from none to overwhelming. Descriptions of taste changes were also collected. Other outcomes included gastrointestinal symptoms collected using the iPOS-renal symptom inventory, nutritional status, and biochemical parameters.

RESULTS

In total, 298 patients were included in our analysis. Taste changes were reported in 38% of this cohort. Taste changes were significantly associated with upper gastrointestinal symptoms (nausea, vomiting, anorexia, and dry/sore mouth) and malnutrition.

CONCLUSIONS

Our findings indicate that taste changes are highly prevalent and probably under-recognized in ESKD. Further investigation of the association with malnutrition is needed. Future trials are needed to evaluate strategies to manage taste changes in this population.

Otorhinolaryngological dysfunctions induced by chronic kidney disease in pre- and post-transplant stages

Purpose

Otorhinolaryngological abnormalities are common complications of chronic kidney disease (CKD) and its treatment. The main aim of this study was to provide a brief and precise review of the current knowledge regarding CKD and its treatment-related influence on head and neck organs.

Methods

The Medline and Web of Science databases were searched using the terms “chronic kidney disease”, “kidney transplantation”, “immunosuppression”, “dialysis” in conjunction with “otorhinolaryngological manifestation”. Articles that did not address the topics, low-quality studies, case reports, and studies based on nonsignificant cohorts were excluded, and the full text of remaining high-quality, novel articles were examined and elaborated on.

Results

Patients with CKD are prone to develop sensorineural hearing loss, tinnitus, recurrent epistaxis, opportunistic infections including oropharyngeal candidiasis or rhino-cerebral mucormycosis, taste and smell changes, phonatory and vestibular dysfunctions, deep neck infections, mucosal abnormalities, gingival hyperplasia, halitosis or xerostomia. Immunosuppressive therapy after kidney transplantation increases the risk of carcinogenesis, both related and not-related to latent viral infection. The most commonly viral-related neoplasms observed in these patients are oral and oropharyngeal cancers, whereas the majority of not-related to viral infection tumors constitute lip and thyroid cancers. CKD-related otorhinolaryngological dysfunctions are often permanent, difficult to control, have a significant negative influence on patient’s quality of life, and can be life threatening.

Conclusion

Patients with CKD suffer from a number of otorhinolaryngological CKD-induced complications. The relationship between several otorhinolaryngological complications and CKD was widely explained, whereas the correlation between the rest of them and CKD remains unclear. Further studies on this subject are necessary.

Factors associated with odour identification in older Indonesian and white Australian adults

BACKGROUND AND AIMS

Among older adults, olfactory dysfunction is associated with cognitive impairment, lower quality of life, and increased mortality. While age is a risk factor for olfactory dysfunction, other risk factors are less well understood, and may vary between ethno-regional groups. This study investigated how associations between odour identification (OI) and various risk factors, as well as cognition and language ability, differed or were similar in two distinct ethno-regional groups of older adults.

METHODS

This cross-sectional study used data from two cohorts: 470 Indonesians (aged 67.4 ± 7.4 years) and 819 white Australians (aged 78.7 ± 4.8 years). Univariate and multivariate analyses explored whether OI test scores were associated with age, sex, education, cholesterol levels, apolipoprotein E ε4 status, smoking, diabetes, hypertension and depression scale scores, or with Mini-Mental State Examination (MMSE) and language test performance.

RESULTS

Univariate analyses identified some factors associated with OI scores in both Indonesians and white Australians, including older age and smoking with lower scores, and MMSE and language test performance with higher scores. Multivariate analyses yielded different and mutually exclusive patterns of associations in the two ethno-regional groups, with language test scores significantly associated with higher OI scores in Indonesians, and age, being male, smoking, having diabetes and higher depression scale scores significantly associated with lower OI scores in white Australians.

CONCLUSION

Ethno-regional differences may need consideration in the attempt to fully understand associations between OI and negative outcomes like dementia and mortality, and interventions for olfactory dysfunction might need to be tailored to specific ethno-regional groups. However, the difference in mean age between cohorts is a limitation of this study, and future studies should aim to compare populations with similar age distributions.

Chronic kidney disease and the olfactory system

Alterations in the sense of smell (dysosmia, anosmia, hyposmia) are frequently experienced by patients with chronic kidney disease. However, currently, the aetiology and consequences are poorly understood, with no effective treatments available to address such impairment. In general, the capacity of olfactory perception is affected in patients with chronic kidney disease (even in those who have not undergone dialysis therapy), and whether these alterations improve after dialysis is disputed. Patients in peritoneal dialysis and haemodialysis have the same olfactory perception defects. Kidney transplantation improves olfactory perception, and one important consequence of such impairment is the potential impact on the patient's nutritional status.