Cystatin C as a marker of cognitive function in elders: findings from the health ABC study

Renal dysfunction in AQP4 NMOSD and MS; a potential predictor of relapse and prognosis

OBJECTIVE

This study aimed to explore the association between kidney function and the risk of relapse as well as prognosis in patients with aquaporin-4 (AQP4)-immunoglobulin G (IgG)-seropositive neuromyelitis optica spectrum disorder (NMOSD).

METHODS

We focused on patients experiencing their first onset of AQP4-IgG-seropositive NMOSD. Data on demographics, disease characteristics, and kidney function were collected, with the primary assessment utilizing the estimated glomerular filtration rate (eGFR). Associations between eGFR and relapse risk were examined using multivariate Cox proportional hazards regression models. Additionally, logistic regression models were employed to evaluate the impact of eGFR on clinical prognosis.

RESULTS

Our analysis revealed glomerular hyperfiltration and impaired urine concentrating ability in patients with AQP4-IgG-seropositive NMOSD. Multivariate Cox proportional hazards regression demonstrated a positive correlation between eGFR and the risk of relapse. Logistic regression analysis further identified higher eGFR as an independent predictor of disease relapse and prognosis in AQP4-IgG-seropositive NMOSD patients.

CONCLUSIONS

The eGFR of patients with AQP4-IgG-seropositive NMOSD emerges as a potential diagnostic biomarker for this condition, indicating its significance in predicting both relapse risk and clinical prognosis.

The Health, Aging, and Body Composition (Health ABC) Study-Ground-Breaking Science for 25 Years and Counting

BACKGROUND

The Health, Aging, and Body Composition Study is a longitudinal cohort study that started just over 25 years ago. This ground-breaking study tested specific hypotheses about the importance of weight, body composition, and weight-related health conditions for incident functional limitation in older adults.

METHODS

Narrative review with analysis of ancillary studies, career awards, publications, and citations.

RESULTS

Key findings of the study demonstrated the importance of body composition as a whole, both fat and lean mass, in the disablement pathway. The quality of the muscle in terms of its strength and its composition was found to be a critical feature in defining sarcopenia. Dietary patterns and especially protein intake, social factors, and cognition were found to be critical elements for functional limitation and disability. The study is highly cited and its assessments have been widely adopted in both observational studies and clinical trials. Its impact continues as a platform for collaboration and career development.

CONCLUSIONS

The Health ABC provides a knowledge base for the prevention of disability and promotion of mobility in older adults.

Cystatins: unravelling the biological implications for neuroprotection

Cystatins, a family of proteins known for their inhibitory role against cysteine proteases, have garnered significant attention in the field of neurodegeneration. Numerous genetic, experimental, and clinical studies concerning cystatin C suggest it plays an important role in the course of neurodegenerative diseases. Its beneficial effects are associated with cysteine protease inhibition, impact on β-amyloid aggregation, as well as regulation of cell proliferation, autophagy, and apoptosis. Cystatin isolated from chicken egg white, called ovocystatin, has been widely used in medical and pharmaceutical research due to its structural and biological similarities to human cystatin C. This article focuses on the potential use of cystatins, with special emphasis on easily obtained ovocystatin, in the treatment of neurodegenerative diseases, such as dementia. The current evidence on cystatin use has shed light on its mechanisms of action and therapeutic implications for neuroprotection and maintenance of cognitive functions.

The association between kidney function, cognitive function, and structural brain abnormalities in community-dwelling individuals aged 50+ is mediated by age and biomarkers of cardiovascular disease

AIMS

Cognitive impairment has been associated with kidney function and chronic kidney disease. Whether this association is due to accelerated cardiovascular disease (CVD) or an independent specific kidney function effect related to toxins is unclear. We investigated the impact of an array of clinical factors, inflammatory biomarkers, and cardiovascular biomarkers on the association between kidney function, cognitive function, and structural brain abnormalities.

METHODS AND RESULTS

We used data from the first and third waves of the TILDA Study, a population-representative prospective cohort of Irish adults aged 50 years and over, based on stratified random sampling (n = 3774). The MRI sub-study included participants who consented to MRI brain imaging in addition to the health assessment. Multivariable linear and mixed-effect longitudinal regression models were fitted separately for each kidney marker/estimated glomerular filtration rate (eGFR) equation after adjusting for baseline age and demographics, clinical vascular risk factors, and biomarkers. Unadjusted analyses showed an association between low eGFR, cognitive dysfunction, and cognitive decline (P < 0.001 for all kidney markers). Kidney function markers were also associated with white matter disease [OR = 3.32 (95% CI: 1.11, 9.98)], total grey matter volume (β = -0.17, 95% CI -0.27 to -0.07), and regional grey matter volumes within areas particularly susceptible to hypoxia (P < 0.001 for all). All the associations decreased after adjusting for age and were also diminished after adjusting for CVD biomarkers. Age and CVD-biomarker score were significant mediators of the adjusted associations between eGFR and cognitive status. These results remained consistent for cross-sectional and longitudinal outcomes and specific cognitive domains.

CONCLUSION

Decreased kidney function was associated with cerebrovascular disease. The association appeared to be mediated predominantly by age and the combination of CVD markers [namely N-terminal pro-B-type natriuretic peptide (NT-proBNP) and Growth Differentiation Factor 15 (GDF15)], supporting the idea that shared biological pathways underline both diseases. Further mechanistic studies of the specific molecular mechanisms that lead to both kidney and cognitive decline are warranted.

Decomposing interaction and mediating effects of race/ethnicity and circulating blood levels of cystatin C on cognitive status in the United States health and retirement study

Background and objectives

Elevated circulating cystatin C is associated with cognitive impairment in non-Hispanic Whites, but its role in racial disparities in dementia is understudied. In a nationally representative sample of older non-Hispanic White, non-Hispanic Black, and Hispanic adults in the United States, we use mediation-interaction analysis to understand how racial disparities in the cystatin C physiological pathway may contribute to racial disparities in prevalent dementia.

Methods

In a pooled cross-sectional sample of the Health and Retirement Study (n = 9,923), we employed Poisson regression to estimate prevalence ratios and to test the relationship between elevated cystatin C (>1.24 vs. ≤1.24 mg/L) and impaired cognition, adjusted for demographics, behavioral risk factors, other biomarkers, and chronic conditions. Self-reported racialized social categories were a proxy measure for exposure to racism. We calculated additive interaction measures and conducted four-way mediation-interaction decomposition analysis to test the moderating effect of race/ethnicity and mediating effect of cystatin C on the racial disparity.

Results

Overall, elevated cystatin C was associated with dementia (prevalence ratio [PR] = 1.2; 95% CI: 1.0, 1.5). Among non-Hispanic Black relative to non-Hispanic White participants, the relative excess risk due to interaction was 0.7 (95% CI: -0.1, 2.4), the attributable proportion was 0.1 (95% CI: -0.2, 0.4), and the synergy index was 1.1 (95% CI: 0.8, 1.8) in a fully adjusted model. Elevated cystatin C was estimated to account for 2% (95% CI: -0, 4%) for the racial disparity in prevalent dementia, and the interaction accounted for 8% (95% CI: -5, 22%). Analyses for Hispanic relative to non-white participants suggested moderation by race/ethnicity, but not mediation.

Discussion

Elevated cystatin C was associated with dementia prevalence. Our mediation-interaction decomposition analysis suggested that the effect of elevated cystatin C on the racial disparity might be moderated by race/ethnicity, which indicates that the racialization process affects not only the distribution of circulating cystatin C across minoritized racial groups, but also the strength of association between the biomarker and dementia prevalence. These results provide evidence that cystatin C is associated with adverse brain health and this effect is larger than expected for individuals racialized as minorities had they been racialized and treated as non-Hispanic White.

Serum cystatin C and mild cognitive impairment: The mediating role of glucose homeostasis

Background

This study explored the mediating role of glucose homeostasis indicators in the relationship between serum cystatin C and mild cognitive impairment (MCI).

Methods

The present study used a cross-sectional design and included 514 participants aged ≥50 years in Beijing, China. The Mini-Mental State Examination was used to assess cognitive function. Serum cystatin C and a comprehensive set of glucose homeostasis indicators were detected, including fasting blood glucose (FBG), glycosylated albumin percentage (GAP), glycated hemoglobin (HbAlc), insulin, and homeostatic model assessment of insulin resistance (HOMA-IR), and beta cell function (HOMA-β). Generalized linear models were used to investigate the associations among cystatin C, glucose homeostasis indicators, and cognitive function. Mediation analysis was conducted to explore potential mediator variables.

Results

In this study of 514 participants, 76 (14.8%) had MCI. Those with cystatin C levels ≥1.09 mg/L had a 1.98-fold higher risk of MCI than those with levels &lt;1.09 mg/L (95% CI, 1.05–3.69). FBG, GAP, and HbA1c increased the risk of MCI, while HOMA-β decreased the risk. Notably, the associations between MCI risk and cystatin C or glucose homeostasis were only founded in diabetes patients. Serum cystatin C was found to be positively associated with HOMA-β (beta (95% CI): 0.20 [0.06, 0.34]), HOMA-IR (0.23 [0.09, 0.36]), and insulin (0.22 [0.09, 0.34]) levels. Moreover, HOMA-β was identified as playing a negative mediating role (proportion mediated: −16%) in the relationship between cystatin C and MCI.

Conclusion

Elevated levels of cystatin C are associated with an increased risk of MCI. The glucose homeostasis indicator, HOMA-β, plays a negative mediating role in the relationship between cystatin C and MCI risk.

Association Between Serum Cystatin C and Cognitive Decline Independently from Creatinine: Evidence from Two Nationally Representative Aging Cohorts

BACKGROUND

Studies on the association between cystatin C based estimated glomerular filtration rate (eGFRcys) and cognitive outcomes yielded inconsistent results.

OBJECTIVE

The present study aimed to examine the potential association of eGFRcys with subsequent cognitive decline rate.

METHODS

A total of 11,503 community-based participants were involved in our analyses, including 5,837 (aged 72.9±6.3; 58.6% women) in the Health and Retirement Study (HRS) from the US and 5,666 (aged 58.1±9.2; 49.0% women) in the China Health and Retirement Longitudinal Study (CHARLS). The association of eGFRcys with subsequent cognitive decline rate was evaluated by linear mixed models.

RESULTS

During 85,266 person-years of follow-up, both baseline elevated serum cystatin C (-0.048 standard deviation [SD]/year per mg/L; 95% confidence interval [CI], -0.060 to -0.036; p < 0.001) and decreased eGFRcys (0.026 SD/year per 30 mL/min/1.73m2; 95% CI, 0.020 to 0.032; p < 0.001) were associated with faster cognitive decline rate after full adjustment. Compared with those had eGFRcys ≥90 mL/min/1.73m2, participants with eGFRcys between 60 to 90 mL/min/1.73m2 (-0.012 SD/year; 95% CI, -0.020 to -0.004; p = 0.004) and those with eGFRcys <60 mL/min/1.73m2 (-0.048 SD/year; 95% CI, -0.058 to -0.039; p < 0.001) experienced statistically significantly faster cognitive decline after adjustment. The associations were independent from serum creatinine/eGFRcre (eGFR that was calculated from serum creatinine).

CONCLUSION

Decreased eGFRcys are significantly associated with faster cognitive decline after full adjustment, independently from serum creatinine/eGFRcre. Serum cystatin C might be a risk factor or a prodromal biomarker of cognitive decline.

Cerebrovascular pulsatility index is higher in chronic kidney disease

Patients with chronic kidney disease (CKD) are more likely to die of cardiovascular diseases, including cerebrovascular disease, than to progress to end-stage kidney disease. Cerebrovascular dysfunction, characterized by reduced cerebrovascular reactivity, cerebral hypoperfusion, and increased pulsatile flow within the brain, precedes the onset of dementia and is linked to cognitive dysfunction. However, whether impaired cerebrovascular function is present in non-dialysis dependent CKD is largely unknown. Using transcranial Doppler, we compared middle cerebral artery (MCA) blood velocity response to hypercapnia (normalized for blood pressure and end-tidal CO₂ ; a measure of cerebrovascular reactivity) and MCA pulsatility index (PI; a measure of cerebrovascular stiffness) in patients with stage 3-4 CKD vs. age-matched healthy controls. We also administered the NIH cognitive toolbox (cognitive function), measured carotid-femoral pulse-wave velocity (PWV; aortic stiffness), and assessed ex vivo nitric oxide (NO) and reactive oxygen species (ROS) production from human brain endothelial cells incubated with serum obtained from study participants. MCA PI was higher in patients with CKD vs. controls; however, normalized MCA blood velocity response to hypercapnia did not differ between groups. Similar results were observed in a validation cohort of midlife and older adults divided by the median estimated glomerular filtration rate (eGFR). MCA PI was associated with greater large-elastic artery stiffness (carotid-femoral PWV), worse executive function (trails B time), lower eGFR, and higher ex vivo ROS production. These data suggest that impaired kidney function is associated with greater cerebrovascular stiffness, which may contribute to the known increased risk for cognitive impairment in patients with CKD.

Evaluating the effects of low-dose simulated galactic cosmic rays on murine hippocampal-dependent cognitive performance

Space exploration has advanced substantially over recent decades and plans to increase the duration of deep space missions are in preparation. One of the primary health concerns is potential damage to the central nervous system (CNS), resulting in loss of cognitive abilities and function. The majority of ground-based research on space radiation-induced health risks has been conducted using single particle simulations, which do not effectively model real-world scenarios. Thus, to improve the safety of space missions, we must expand our understanding of the effects of simulated galactic cosmic rays (GCRs) on the CNS. To assess the effects of low-dose GCR, we subjected 6-month-old male BALB/c mice to 50 cGy 5-beam simplified GCR spectrum (¹H, ²⁸Si, ⁴He, ¹⁶O, and ⁵⁶Fe) whole-body irradiation at the NASA Space Radiation Laboratory. Animals were tested for cognitive performance with Y-maze and Morris water maze tests 3 months after irradiation. Irradiated animals had impaired short-term memory and lacked spatial memory retention on day 5 of the probe trial. Glial cell analysis by flow cytometry showed no significant changes in oligodendrocytes, astrocytes, microglia or neural precursor cells (NPC's) between the sham group and GCR group. Bone marrow cytogenetic data showed a significant increase in the frequency of chromosomal aberrations after GCR exposure. Finally, tandem mass tag proteomics identified 3,639 proteins, 113 of which were differentially expressed when comparing sham versus GCR exposure (fold change > 1.5; p < 0.05). Our data suggest exposure to low-dose GCR induces cognitive deficits by impairing short-term memory and spatial memory retention.

Association of kidney function and brain health: A systematic review and meta-analysis of cohort studies

OBJECTIVE

This study aimed to evaluate the bidirectional association between the kidney dysfunction and the brain health, including structural and functional abnormalities.

DESIGN

Systematic review and meta-analysis with network meta-analysis for outcomes with different estimated glomerular filtration rate (eGFR) ranges.

DATA SOURCES

PubMed, Embase database, Cochrane library and Web of Science (up to Dec. 2021).

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Longitudinal studies that provided evidence of the impact of kidney function estimated from eGFR and urine albumin-to-creatinine ratio (UACR) or chronic kidney disease (CKD) on structural and functional brain abnormalities, and those that provided evidence of the opposite relationship. Studies with study population mean age under 18 years old were excluded.

MAIN OUTCOME MEASURES

Two independent reviewers screened the included studies, extracted the data, and assessed the risk of bias. We performed a random-effects meta-analysis and a network meta-analysis for outcomes with compatible data. We assessed the risk of bias using the Newcastle-Ottawa Quality Assessment Scale criteria (NOS). Subgroup and sensitivity analyses were conducted to explore heterogeneity in the meta-analyses. Inconsistency analyses using the node-splitting method were performed to confirm the results of network meta-analysis.

RESULTS

A total of 53 studies with 3037,357 participants were included in the current systematic review. Among these, 16 provided evidence of structural brain abnormalities, and 38 provided evidence of cognitive impairment and dementia. Analysis of evidence of categorical kidney function showed a positive association between kidney dysfunction and cerebral small vessel disease (cSVD) (relative risk (RR) 1.77, 95% confidence interval (CI) 1.40-2.24, I² = 0.0%), but such results were not found in the analyses of evidence where the kidney function was measured as a continuous variable. Meanwhile, analysis of 28 prior longitudinal studies with 194 compatible sets of data showed that the worse kidney function as categorical variables was related to a greater risk of global brain cognitive disorder (RR 1.28, 95% CI 1.20-1.36, I² = 82.5%).

CONCLUSIONS

In this systematic review and meta-analysis, we found a positive association between CKD and functional brain disorders. However, the relationship between the kidney dysfunction and structural abnormalities in the brain remains controversial. As for the opposite relationship, structural brain abnormalities, especially cerebral microbleeds and silent infarction, but not functional brain abnormalities, are associated with worse renal function. In addition, a higher UACR, but not a lower eGFR, was associated with a higher risk of Alzheimer's disease and vascular dementia.

Mild to moderate decrease in eGFR and cognitive decline in older adults

BACKGROUND

Whether mild to moderately low estimated glomerular filtration rate (eGFR) is associated with cognitive decline in older adults is not clear. We evaluated changes in cognition in relation to baseline eGFR in older adults participating in the Alzheimer's Disease Neuroimaging Initiative (ADNI).

METHODS

This is a longitudinal secondary analysis of an established observational cohort. We used data from the ADNI, an National Institutes of Health-funded, multicenter longitudinal observational study that includes participants with and without cognitive impairment who were administered a comprehensive battery of neuropsychological tests every 6 months. We related the Chronic Kidney Disease Epidemiology Collaboration eGFR with previously validated cognition composite scores for memory (ADNI-Mem) and executive function (ADNI-EF) in multivariable linear regression analysis adjusted for age, sex, race and level of education.

RESULTS

A total of 1127 ADNI participants (mean age 74 ± 7 years, 57% men, 97% Caucasian, mean follow-up 6 ± 2.6 years) were included in the analysis. The mean baseline eGFR was 76 ± 19 mL/min/1.73 m2, with 6% with eGFR <45, 22% with eGFR 45-<60, 51% with eGFR 60-90 and 21% with eGFR >90 mL/min/1.73 m2 at baseline. Both ADNI-Mem and ADNI-EF scores declined over time. In the multivariable linear regression model, older age (β = -0.117, P = 0.01), female sex (β = 0.312, P < 0.001) and lower education (β = 0.079, P < 0.001) were associated with a decline in ADNI-Mem scores, whereas baseline eGFR (each 10 mL/min/1.73 m2 change) was not {β = -0.03 [confidence interval (CI) -0.06-0.001], P = 0.11}. Similarly, older age (β = -0.278, P < 0.001) and lower education (β = 0.099, P < 0.001) were associated with a decline in ADNI-EF scores, whereas baseline eGFR was not [β = 0.004 (95% CI -0.04-0.04), P = 0.84].

CONCLUSIONS

In this cohort from the ADNI study, there was no association between baseline eGFR and cognitive decline in older adults with mild to moderately low eGFR.

12-month survival in nonagenarians inside the Mugello study: on the way to live a century

Background

Life expectancy has increased over the last century and a growing number of people is reaching age 90 years and over. However, data on nonagenarians’ health trends are scarce due to difficulties in investigating this specific population. This study aims to identify risk factors for one-year mortality in nonagenarians using data collected within the “Mugello Study”.

Methods

Complete information on sociodemographic data, cognitive and functional status, lifestyle, medical history, and drug use was collected from 433 nonagenarians, as well as information about survival after 1 year from the interview.

Results

The sample included 314 women (72.5%) and 119 men (27.5%) with a median age of 92 years (range 90-99 years). The mortality rate was 20.3% (88 deaths). After adjustment for age and sex, a significantly higher risk of dying within 12 months was observed in individuals with more severe cognitive impairment (HR = 5.011, p < 0.001), more severe disability in basic activities of daily living (HR = 4.193, p < 0.001), sedentary lifestyle (HR = 3.367, p < 0.001), higher number of drugs assumed (HR = 1.118, p = 0.031), and kidney dysfunction (HR = 2.609, p = 0.004). When all the variables were included in the analysis, only older age (HR = 1.079, p = 0.048), lower cognitive function (HR = 2.859, p = 0.015), sedentary lifestyle (HR = 2.030, p = 0.026), and kidney dysfunction (HR = 2.322, p = 0.018) remained significantly associated with reduced survival.

Conclusions

Data from the Mugello study support the hypothesis that survival at 12 months in nonagenarians is not a stochastic process and that older age, reduced cognitive function, sedentary lifestyle, and the presence of kidney dysfunction are associated with mortality.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-022-02908-9.

Association of Serum Levels of Cystatin C and Cognition in a Cohort of Egyptian Elderly Patients with Chronic Kidney Disease

Chronic kidney disease (CKD) and dementia are common morbidities of elders. Serum cystatin C has been suggested to be an ideal marker for kidney function. The current study aimed to detect the serum levels of cystatin C in CKD patients and to correlate these levels to cognitive performance. The study involved 90 subjects aged 65 years and more, divided into two groups: Group 1: 60 patients with CKD, and Group 2: 30 control participants. Exclusion criteria included cardiac failure, hepatic failure, thyroid diseases, dialysis for more than one month, polycystic kidney disease, organ transplantation, and immunosuppressive therapy within the past six months. All participants had routine laboratory workup, serum cystatin C using enzyme-linked immunosorbent assay kits, and cognitive assessment using mini-mental state examination (MMSE). Serum cystatin level was significantly high in CKD patients while MMSE scores were significantly lower in CKD patients. A high significant negative correlation was found between serum cystatin C levels and both degree of cognitive impairment and glomerular filtration rate (GFR). Also, a significant positive correlation was found between the degree of cognitive impairment and GFR levels. Serum cystatin levels are significantly associated with cognitive impairment in CKD patients, and this correlation becomes more evident with the worsening of CKD stages. That may help in better understanding of the pathogenesis of dementia in CKD patients with the emergence of therapeutic options depending on these data.

Association between serum cystatin C level and post-stroke cognitive impairment in patients with acute mild ischemic stroke

BACKGROUND

Mild ischemic stroke (MIS) has been proved to be closely related to post-stroke cognitive impairment (PSCI). However, there are relatively few studies on the risk factors of MIS. We aimed to evaluate the relationship between serum cystatin C (CysC) level and cognitive function in patients with acute MIS.

METHODS

Four hundred consecutive patients with acute MIS were screened and 281 patients were eligible for this study. The serum CysC levels were detected within 24 h after admission. Cognitive function was assessed by Montreal Cognitive Assessment (MoCA) at 3 months after acute MIS. Logistic regression was used to identify the predictors of PSCI, and the receiver operating characteristic (ROC) curve was applied to explore the optimal cut-off value.

RESULTS

One hundred sixty-four (58.4%) patients were diagnosed with PSCI at 3 months follow-up. The serum CysC levels in patients with PSCI were significantly higher than patients without PSCI (p < .001). The binary logistic regression analysis showed that higher serum CysC level was an independent predictor for PSCI at 3 months (odds ratio [OR], 5.745; 95% confidence interval, [CI], 1.089-30.311; p = 0.039). The ROC curve showed that area under the curve (AUC) was 0.723, and at a 0.945 mg/l CysC cut-off point, the sensitivity and specificity for PSCI at 3 months were 79.9% and 58.1%, respectively.

CONCLUSION

Our findings suggested that the serum CysC levels were increased after acute MIS, and higher serum CysC levels at baseline might be an independent risk factor for PSCI in patients with acute MIS, but further research are warranted.

Changes in Serum Cystatin C Levels and the Associations With Cognitive Function in Alzheimer's Disease Patients

Background and Objective

Cystatin C is indicated to be involved in the pathogenesis of Alzheimer's disease (AD) and cognitive impairment. Our objective is to examine the serum Cystatin C levels, and to clarify the correlations between serum Cystatin C and cognitive performance in Chinese AD patients.

Methods

The serum Cystatin C concentrations in AD patients and age, sex, and body mass index (BMI) matched-healthy controls were measured. The cognitive functions of the AD patients were evaluated by using the Mini-mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA). The severity of dementia was determined with clinical dementia rating (CDR).

Results

A total of 463 AD patients and 1,389 matched healthy subjects were included. AD patients had higher serum Cystatin C than healthy controls. Serum cystatin C levels were correlated with MoCA scores in AD patients. In an ordinal logistic regression model, AD patients with higher serum cystatin C levels had increased odds of severe cognitive dysfunction.

Conclusion

Our study suggested that AD patients had higher levels of serum cystatin C than age/sex/BMI-matched normal control subjects. Higher serum cystatin C may be associated with worse cognitive performance, but more studies are required to verify such association.

The impact of uremic toxins on Alzheimer's disease

Alzheimer's disease (AD) is the most common type of dementia, pathologically characterized by accumulation of senile plaques and neurofibrillary tangles. Chronic kidney disease (CKD) is highly prevalent in elderly population closely associated with occurrence of dementia. Recent epidemiological and experimental studies suggest a potential association of CKD with AD. Both diseases share a panel of identical risk factors, such as type 2 diabetes; and hypertension. However, the relationship between CKD and AD is unclear. Lower clearance of a panel of uremic toxin including cystatin-C, guanidine, and adiponectin due to CKD is implied to contribute to AD pathogenesis. In this review we summarize the current evidence from epidemiological, experimental and clinical studies on the potential contribution of uremic toxins to AD pathogenesis. We describe outstanding questions and propose an outlook on the link between uremic toxins and AD.

Precision Medicine in Alzheimer's Disease: Investigating Comorbid Common Biological Substrates in the Rat Model of Amyloid Beta-Induced Toxicity

Alzheimer's disease (AD), one of the most widespread neurodegenerative disorder, is a fatal global burden for the elder population. Although many efforts have been made, the search of a curative therapy is still ongoing. Individuating phenotypic traits that might help in investigating treatment response is of growing interest in AD research. AD is a complex pathology characterized by many comorbidities, such as depression and increased susceptibility to pain perception, leading to postulate that these conditions may rely on common biological substrates yet to be determined. In order to investigate those biological determinants to be associable with phenotypic traits, we used the rat model of amyloid beta-induced toxicity. This established model of early phase of AD is obtained by the intracerebroventricular injection of soluble amyloid beta1-42 (Aβ) peptide 7 days before performing experiments. In this model, we have previously reported increased immobility in the forced swimming test, reduced cortical serotonin levels and subtle alterations in the cognitive domain a depressive-like phenotype associated with subtle alteration in memory processes. In light of evaluating pain perception in this animal model, we performed two different behavioral tests commonly used, such as the paw pressure test and the cold plate test, to analyze mechanical hyperalgesia and thermal allodynia, respectively. Behavioural outcomes confirmed the memory impairment in the social recognition test and, compared to sham, Aβ-injected rats showed an increased selective susceptibility to mechanical but not to thermal stimulus. Behavioural data were then corroborated by neurochemical and biochemical biomarker analyses either at central or peripheral level. Data showed that the peptide injection evoked a significant increase in hypothalamic glutamate, kynurenine and dopamine content, while serotonin levels were reduced. Plasma Cystatin-C, a cysteine protease, was increased while serotonin and melatonin levels were decreased in Aβ-injected rats. Urinary levels paralleled plasma quantifications, indicating that Aβ-induced deficits in pain perception, mood and cognitive domain may also depend on these biomarkers. In conclusion, in the present study, we demonstrated that this animal model can mimic several comorbid conditions typical of the early phase of AD. Therefore, in the perspective of generating novel therapeutic strategies relevant to precision medicine in AD, this animal model and the biomarkers evaluated herein may represent an advantageous approach.

Multi-omics of human plasma reveals molecular features of dysregulated inflammation and accelerated aging in schizophrenia

Schizophrenia is a devastating psychiatric illness that detrimentally affects a significant portion of the worldwide population. Aging of schizophrenia patients is associated with reduced longevity, but the potential biological factors associated with aging in this population have not yet been investigated in a global manner. To address this gap in knowledge, the present study assesses proteomics and metabolomics profiles in the plasma of subjects afflicted with schizophrenia compared to non-psychiatric control patients over six decades of life. Global, unbiased analyses of circulating blood plasma can provide knowledge of prominently dysregulated molecular pathways and their association with schizophrenia, as well as features of aging and gender in this disease. The resulting data compiled in this study represent a compendium of molecular changes associated with schizophrenia over the human lifetime. Supporting the clinical finding of schizophrenia's association with more rapid aging, both schizophrenia diagnosis and age significantly influenced the plasma proteome in subjects assayed. Schizophrenia was broadly associated with prominent dysregulation of inflammatory and metabolic system components. Proteome changes demonstrated increased abundance of biomarkers for risk of physiologic comorbidities of schizophrenia, especially in younger individuals. These findings advance our understanding of the molecular etiology of schizophrenia and its associated comorbidities throughout the aging process.

Kidney Function Is Not Related to Brain Amyloid Burden on PET Imaging in The 90+ Study Cohort

Cognitive decline is common in chronic kidney disease (CKD). While the evidence of vascular cognitive impairment in this population is robust, the role of Alzheimer's pathology is unknown. We evaluated serum cystatin C-estimated glomerular filtration rate (eGFR), brain amyloid-β positron emission tomography (PET) imaging, and cognitive function in 166 participants from The 90+ Study. Mean age was 93 years (range 90-107) and 101 (61%) were women; 107 participants had normal cognitive status while 59 participants had cognitive impairment no dementia (CIND) or dementia. Mean ± standard deviation cystatin C was 1.59 ± 0.54 mg/L with eGFR 40.7 ± 18.7 ml/min/1.73m2. Higher amyloid-β burden was associated with dementia, but not with age, diabetes, hypertension, or cardiovascular disease. We found no association between brain amyloid-β burden and cystatin C eGFR. We previously reported that kidney function was associated with cognition and cerebral microbleeds in the same cohort of oldest-old adults (90+ years old). Collectively, these findings suggest that microvascular rather than Alzheimer's pathology drives CKD-associated cognitive dysfunction in this population.

Cystatin C and Risk of Mild Cognitive Impairment: A Systematic Review and Meta-Analysis

INTRODUCTION

Cystatin C (Cys C) has been found as a novel biomarker of neurodegenerative diseases, such as dementia and Alzheimer's disease. Published studies on the role of Cys C as a biomarker of mild cognitive impairment (MCI) have not been reviewed systematically.

OBJECTIVE

Present meta-analysis was performed to elucidate the association between Cys C and risk of MCI.

METHODS

A comprehensive search was performed in PubMed, EMBASE, Cochrane Library, Trip databases, Worldwide Science, and Google Scholar from January 1, 1950, to April 30, 2020. Standardized mean difference (SMD) with 95% confidence interval (CI) using fixed or random effect models were used to calculate summary estimates. Quality of evidence was also assessed using the Diagnostic Accuracy Quality Scale (DAQS) and grading quality of evidence and strength of recommendations approach.

RESULTS

In our meta-analysis, 12 studies with a total of 2,433 MCI patients and 1,034 controls were included. Our findings suggest a strong association between increased levels of Cys C and risk of MCI as compared to control subjects (SMD = 2.39, 95% CI = 0.22-4.57). Subgroup analysis based on ethnicity, a significant association for the high level of Cys C with the risk of MCI was observed in the Asian population (SMD = 1.63, 95% CI = 0.44-2.82) but not in the Caucasian population (SMD = 2.80, 95% CI = [-0.66]-6.26).

CONCLUSION

Cys C was associated with MCI, and it could be considered as a predictor for the risk of cognitive impairment.

Kidney Function, Kidney Function Decline, and the Risk of Dementia in Older Adults: A Registry-Based Study

OBJECTIVE

Community-based reports regarding the association between the estimated glomerular filtration rate (eGFR) and dementia risk show conflicting results. The aim of this study is to investigate the links among kidney function, kidney function decline, and dementia incidence.

METHODS

We analyzed the association of eGFR with the risk of dementia (defined as a new dementia diagnosis or initiation of dementia treatments) among 329,822 residents of Stockholm who accessed health care during 2006 to 2011, were ≥65 years of age, had no history of dementia, or underwent kidney replacement therapy. We also estimated the rate of eGFR decline among 205,622 residents with repeated eGFR measurements during the first year of observation and investigated its association with subsequent dementia risk.

RESULTS

We detected 18,983 cases of dementia (5.8% of participants) over a median follow-up of 5 years. Dementia incidence rates were progressively higher with lower eGFR: from 6.56/1,000 person-years in those with eGFR of 90 to 104 mL/min to 30.28/1,000 person-years in those with eGFR <30 mL/min. After multivariable adjustment, lower eGFR was associated with a higher dementia risk (hazard ratio [HR] 1.71, 95% confidence interval [CI] 1.54-1.91 in eGFR 30-59 mL/min; HR 2.62, 95% CI 1.91-3.58 in eGFR <30 mL/min) compared with eGFR of 90 to 104 mL/min. A steeper decline in eGFR (decline >2 mL/min/1.73 m2/y) within 1 year was associated with higher dementia risk. Risk magnitudes were stronger for vascular dementia than for Alzheimer dementia. As many as 10% (95% CI 6%-14%) of dementia cases could be attributed to eGFR <60 mL/min/1.73 m2, a proportion higher than that attributed to other dementia risk factors such as cardiovascular disease and diabetes.

CONCLUSIONS

Both lower kidney function and steeper kidney function decline are associated with the development of dementia.

Level and Change in N-Terminal Pro-B-Type Natriuretic Peptide and Kidney Function and Survival to Age 90

BACKGROUND

Many traditional cardiovascular risk factors do not predict survival to very old age. Studies have shown associations of estimated glomerular filtration rate (eGFR) and N-terminal pro-B-type natriuretic peptide (NT-pro-BNP) with cardiovascular disease and mortality in older populations. This study aimed to evaluate the associations of the level and change in eGFR and NT-pro-BNP with longevity to age 90 years.

METHOD

The population included participants (n = 3,645) in the Cardiovascular Health Study, aged between 67 and 75 at baseline. The main exposures were eGFR, calculated with the Berlin Initiative Study (BIS) 2 equation, and NT-pro-BNP, and the main outcome was survival to age 90. Mixed models were used to estimate level and change of the main exposures.

RESULTS

There was an association between baseline level and change of both eGFR and NT-pro-BNP and survival to 90, and this association persisted after adjustment for covariates. Each 10 mL/min/1.73 m2 higher eGFR level was associated with an adjusted odds ratio (OR) of 1.23 (95% CI: 1.13, 1.34) of survival to 90, and a 0.5 mL/min/1.73 m2 slower decline in eGFR was associated with an OR of 1.51 (95% CI: 1.31, 1.74). A twofold higher level of NT-pro-BNP level had an adjusted OR of 0.67 (95% CI: 0.61, 0.73), and a 1.05-fold increase per year in NT-pro-BNP had an OR of 0.53 (95% CI: 0.43, 0.65) for survival to age 90.

CONCLUSION

eGFR and NT-pro-BNP appear to be important risk factors for longevity to age 90.

Kidney function and dementia risk in community-dwelling older adults: the Shanghai Aging Study

BACKGROUND

Association between kidney dysfunction and dementia has been studied in western cohorts, but with inconsistent conclusions which may be due to the different measurements of kidney function. We aim to verify the hypothesis that lower levels of kidney function would be associated with increased risk of incident dementia in Chinese elderly.

METHODS

One thousand four hundred twelve dementia-free participants aged 60 years or older from the Shanghai Aging Study were enrolled and followed up for 5.3 years on average. Glomerular filtration rate (GFR) was calculated by using combined creatinine-cystatin C CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation. Diagnoses of incident dementia and Alzheimer's disease (AD) were established using DSM-IV and NINCDS-ADRDA criteria based on medical, neurological, and neuropsychological examinations to each participant. Cox proportional regression was used to analyze the association of baseline GFR_crcys levels with incident dementia/AD, adjusting age, gender, education years, APOE-ε4, diabetes, hypertension, baseline Mini-Mental State Examination score, and proteinuria.

RESULTS

A total of 113 (8%) and 84 (7%) participants developed dementia and AD. Comparing to participants with high GFR_crcys (≥ 80 ml/min/1.73 m²), participants with low (< 67 ml/min/1.73 m²) and moderate GFR_crcys (67 ≤ GFR < 80 ml/min/1.73 m²) had increased risk of incident dementia with hazard ratios (HRs) of 1.87 (95% CI 1.02-3.44) and 2.19 (95% CI 1.21-3.95) after adjustment for confounders, respectively. Low (HR = 2.27 [95%CI 1.10-4.68]) and moderate (HR = 2.14 [95% CI 1.04-4.40]) GFR_crcys at baseline was also independently associated with incident AD after adjustments when comparing to high GFR_crcys. The significant association between GFR_crcys and dementia risk was observed in female but not in male participants.

CONCLUSIONS

GFR_crcys may be considered as a marker of an individual's vulnerability to the increased risk of cognitive decline.

Fibroblast growth factor 23 and cognitive impairment: The health, aging, and body composition study

BACKGROUND

Concentrations of fibroblast growth factor 23 (FGF-23), a hormone that regulates phosphorus and vitamin D metabolism, increase as kidney function declines. Excess fibroblast growth factor 23 may impact brain function through promotion of vascular disease or through direct effects on neuronal tissue.

METHODS

In the Healthy Aging and Body Composition Study, a longitudinal observational cohort of well-functioning older adults, intact serum FGF-23 was assayed in 2,738 individuals. Cognitive function was assessed at baseline and longitudinally at years 3, 5, and 8 by administration of the Modified Mini Mental State Examination (3MSE), a test of global cognitive function, and the Digit Symbol Substitution Test (DSST), a test primarily of executive function. The associations between FGF-23 and baseline cognitive function and incident cognitive impairment were evaluated using logistic and Poisson regression respectively, and were adjusted for demographics, baseline estimated glomerular filtration rate (eGFR), urine albumin/creatinine ratio, comorbidity, and other measures of mineral metabolism including soluble klotho.

RESULTS

The mean (SD) age was 74(3) years, with 51% female, and 39% black. The median (25th, 75th) FGF-23 concentration was 47 pg/mL (37, 60). Three hundred ninety-two individuals had prevalent cognitive impairment by the 3MSE and 461 by the DSST. There was no observed association between FGF-23 and baseline cognitive function for either cognitive test. There were 277 persons with incident cognitive impairment by 3MSE, and 333 persons with incident cognitive impairment by DSST. In fully adjusted models, each two-fold higher concentration of baseline FGF-23 was not associated with incident cognitive impairment by the 3MSE (IRR = 1.02[0.88, 1.19] fully adjusted model) or by the DSST (IRR = 0.98 [0.84, 1.15]. We saw no difference when analyses were stratified by eGFR greater than or less than 60 ml/min/1.73m2.

CONCLUSION

Intact FGF-23 was not associated with baseline cognitive function or incident cognitive impairment in this cohort well-functioning older adults.

Abnormal rich club organization in end-stage renal disease patients before dialysis initiation and undergoing maintenance hemodialysis

Background

End-stage renal disease (ESRD) patients are at a substantially higher risk for developing cognitive impairment compared with the healthy population. Dialysis is an essential way to maintain the life of ESRD patients. Based on previous research, there isn’t an uncontested result whether cognition was improved or worsened during dialysis.

Methods

To explore the impact of dialysis treatment on cognitive performance, we recruited healthy controls (HCs), predialysis ESRD patients (predialysis group), and maintenance hemodialysis ESRD patients (HD group). All ESRD patients performed six blood biochemistry tests (hemoglobin, urea, cystatin C, Na+, K+, and parathyroid hormone). Neuropsychological tests were used to measure cognitive function. By using diffusion tensor imaging and graph-theory approaches, the topological organization of the whole-brain structural network was investigated. Generalized linear models (GLMs) were performed to investigate blood biochemistry predictors of the neuropsychological tests and the results of graph analyses in the HD group and predialysis group.

Results

Neuropsychological analysis showed the HD group exhibited better cognitive function than the predialysis group, but both were worse than HCs. Whole-brain graph analyses revealed that increased global efficiency and normalized shortest path length remained in the predialysis group and HD group than the HCs. Besides, a lower normalized clustering coefficient was found in the predialysis group relative to the HCs and HD group. For the GLM analysis, only the Cystatin C level was significantly associated with the average fiber length of rich club connections in the predialysis group.

Conclusions

Our study revealed that dialysis had a limited effect on cognitive improvement.

Physical Activity Amount and Cognitive Impairment in Korean Elderly Population

The relationship between physical activity amount and cognitive function in elderly Koreans has received little attention. This study therefore aimed to understand the independent and common link between cognitive function and physical activity levels among elderly Korean adults. This study recruited a total of 2746 elderly adults (1348 males and 1398 females). All participants were assessed for cognitive functioning using the Korean Dementia Screening Questionnaire Cognition (KDSQ-C). The computerized Korean version short form of the International Physical Activity Questionnaire (IPAQ) used in this study was entirely based on the long, self-administered, usual week-long IPAQ found in the IPAQ manual of operation. In the unadjusted model, elderly adults who met the recommended level of moderate-to-vigorous physical activity were more likely to have a sufficient level of cognitive function. Hemoglobin, creatinine, cholesterol (TC), triglycerides (TG), LDL-C, and HDL-C differed significantly between groups. A negative correlation was found between KDSQ-C score and the moderate-to-vigorous physical activity (MVPA) amount per week. Physical activity amount is associated with cognition function in Korean elderly adults. Increasing physical activity may improve hemoglobin and creatinine and be involved in improving serum lipid profiles in elderly adults. Thus, physical activity has been suggesting as a useful tool to reduce the risk of cognitive function associated with aging.

Is kidney function associated with cognition and mood in late life? : The Screening for CKD among Older People across Europe (SCOPE) study

Background

Chronic kidney disease (CKD), cognitive impairment and depression share common risk factors. Previous studies did not investigate the possible association between kidney function and cognitive and mood disorders in older persons in a broad range of kidney function. The present study explored associations between kidney function, cognition and mood in outpatients of 75 years and over.

Methods

Baseline data of 2252 participants of the SCOPE study, an international multicenter cohort observational study,were used in which community-dwelling persons of 75 years and over were enrolled to screen for CKD Kidney function was estimated with the BIS1-eGFR equation, cognition was assessed with the Mini-Mental State Examination (MMSE) and mood with the Geriatric Depression Scale 15 items (GDS-15). Characteristics were compared across stages of CKD. Mean eGFR values were also compared across categories of MMSE (< 24, 24–26, ≥27) and between groups with high and low score on the GDS-15 (> 5/≤5).

Results

In total, 63% of the population had an eGFR < 60 mL/min. In advanced stages of CKD, participants were older and more often men than in earlier stages (p < 0.001). Cardiovascular diseases and diabetes mellitus were more often found in those in advanced stages of CKD (p < 0.001), and also cumulative comorbidity scores were higher than in those in earlier stages (p < 0.001). Median MMSE was 29 in CKD stage 1–2 and 3, and 30 in CKD stage 4, whereas median GDS-15 score was 2 in all stages of CKD. Mean values of eGFR did not differ across categories of MMSE or between groups with high and low score on the GDS-15. Stratification for albuminuria did not change these results.

Conclusions

Older persons in more advanced stages of CKD did not have lower cognitive scores or higher rates of depressive symptoms than older persons in earlier stages. Future longitudinal studies might give information on the possible effect of kidney function on cognition and mood in late life.

Trial registration

This study was registered prospectively on 25th February 2016 at clinicaltrials.gov (NCT02691546).

Cystatin C, cognition, and brain MRI findings in 90+-year-olds

Chronic kidney disease is emerging as a novel risk factor for cerebrovascular disease, but this association remains largely unexplored in older adults. Cystatin C is a more accurate measure than creatinine of kidney function in the elderly. We evaluated cystatin C, cognitive function, and brain imaging in 193 participants from The 90+ Study neuroimaging component. The mean age was 93.9 years; 61% were women. Mean cystatin C was 1.62 mg/L with estimated glomerular filtration rate 39.2 mL/min/1.73 m². Performance on measures of global cognition, executive function, and visual-spatial ability declined at higher tertiles of cystatin C (lower kidney function). Higher cystatin C was significantly associated with infratentorial microbleeds and lower gray matter volume. Adjusted risk of incident dementia was increased in the middle and high cystatin C tertile groups compared with the low group (hazard ratio in highest tertile 3.81 [95% confidence interval 1.14-12.7]), which appeared to be explained in part by the presence of cerebral microbleeds. Overall, cystatin C was associated with cognitive performance, brain imaging pathology, and decline to dementia in this oldest-old cohort.

Plasma Cystatin C Associates With HIV-Associated Neurocognitive Disorder but Is a Poor Diagnostic Marker in Antiretroviral Therapy-Treated Individuals

OBJECTIVE

To examine associations between plasma cystatin C and neurocognitive impairment (NCI) and its performance as a diagnostic marker before and during initial antiretroviral therapy (ART).

METHODS

Multivariable logistic regression and generalized estimating equations examined associations with NCI, determined by neuropsychological measurements, in participants of a 48-week randomized clinical trial of initial ART. Receiver operator characteristic curves examined diagnostic models of NCI.

RESULTS

Cystatin C was associated with NCI before ART [odds ratio (OR) 3.4 (95% CI: 1.2 to 9.4) for each 2-fold increase in baseline levels] and during 48 weeks of ART, in models that excluded baseline measurements [OR 3.0 (1.2 to 7.8) for each 2-fold increase in time-updated levels]. The strength of association increased with more severe impairment using HIV-associated neurocognitive disorder criteria [OR 2.2 (0.8 to 6.0) with asymptomatic NCI and OR 4.0 (1.5 to 11.0) with mild neurocognitive disorder or HIV-associated dementia vs. no impairment, for each 2-fold increase in time-updated levels] or by global development score [OR 2.6 (1.1 to 6.3) with mild impairment and OR 4.6 (1.1 to 18.9) with moderate or severe impairment vs. no impairment]. Cystatin C performed poorly as a diagnostic marker for NCI, however, with an area under the receiver operator characteristic curve of 0.58 at baseline and 0.54 at week 48.

CONCLUSIONS

Higher plasma cystatin C levels were significantly associated with NCI, but these levels did not seem to be useful as a diagnostic marker for this condition.

Association Between Cystatin C and Cardiac Function and Long-Term Prognosis in Patients with Chronic Heart Failure

Background

The aim of this study was to investigate the association between cystatin C and cardiac function and long-term prognosis in patients with chronic heart failure (CHF).

Material/Methods

We selected 418 CHF patients admitted to our hospital as subjects. Patients were divided into 3 groups according to the cystatin C level (Quantile 1 group: 0.65–1.04 mg/L, Quantile 2 group: 1.05–1.35 mg/L, and Quantile 3 group: 1.36–7.84 mg/L), and patients were followed up for 5 years. We used odds ratio (OR) and 95% confidence interval (CI) to compare the results.

Results

The cystatin C and NT-ProBNP level in the cardiac function grade (NYHA) class IV group were higher than those in the class III group (P<0.05). Pearson correlation analysis showed that there was a positive correlation between cystatin C and NT-ProBNP log₁₀ transform in CHF patients (r=0.411). During 5-year follow-up, 231 patients died and the 5-year all-cause mortality rate was 55.26% (231/418). There was a significant difference in 5-year all-cause mortality among the 3 groups (P for trend=0.010). After adjusting for potential confounders by multivariate regression analysis, the Quantile 2 group vs. Quantile 1 group were OR=0.83, 95% CI 0.51 to 1.35, P=0.448, and the Quantile 3 group vs. Quantile 1 group were OR=1.71, 95% CI. 1.04 to 2.82, P=0.034. Curve fitting showed that cystatin C was positively correlated with 5-year all-cause mortality in CHF patients.

Conclusions

Cystatin C was positively correlated with cardiac function and NT-ProBNP in CHF patients. Cystatin C could be used as a serological index to evaluate the long-term prognosis of CHF patients.

Systemic Inflammation and Cardio-Renal Organ Damage Biomarkers in Middle Age Are Associated With Physical Capability Up to 9 Years Later

Supplemental Digital Content is available in the text.

Background:

Physical capability, a key component of healthy aging, is associated with cardiovascular and other risk factors across life. We investigated whether midlife biomarkers of heart and kidney damage capturing the cumulative impact of long-term adverse exposures were associated with the level and decline in physical capability over 9 years of follow-up, taking account of systemic inflammatory biomarkers and conventional cardiovascular risk factors.

Methods:

We used data on 1736 men and women from the oldest British birth cohort study with walking speed, chair rise speed, balance time, and grip strength assessed at ages 60 to 64 and 69 years. We tested associations between logged and standardized measures of cystatin C, NT-proBNP (N-terminal pro-B-type natriuretic peptide), interleukin (IL)-6, and E-selectin at age 60 to 64 years with performance at age 69 years, adjusting for sex, height, and body mass index; then for performance at age 60 to 64 years. These biomarkers were mutually adjusted, and additionally adjusted for cardiovascular risk factors (pulse pressure, total/high density lipoprotein cholesterol, glycosylated hemoglobin), diabetes mellitus, cardiovascular and kidney disease, smoking status, and lifetime socioeconomic position.

Results:

Cystatin C, NT-proBNP, and IL-6 (but not E-selectin) were inversely associated with all outcomes, adjusted for sex, height, and body mass index. For example, a 1-SD increase in logged NT-proBNP was associated with weaker grip (−0.63 kg, 95% CI, −0.99 to −0.28); the equivalent association for cystatin C was −0.60 kg (95% CI, −0.94 to −0.25) and for IL-6 was −0.76 kg (95% CI, −1.11 to −0.41). Most associations remained, albeit attenuated, after adjustment for previous performance and mutual adjustment of the biomarkers. NT-proBNP and IL-6 (but not cystatin C) were more strongly associated with the outcomes than many of the conventional risk factors after mutual adjustment.

Conclusions:

Higher levels of NT-proBNP may identify those in midlife at risk of accelerated physical decline. Before considering the use of NT-proBNP for risk stratification, further research should untangle whether these associations exist because the biomarker is an integrated measure of cumulative exposures to relevant stressors across life, or whether it is marking additional risk pathways. Randomized trials to reduce the rate of decline in physical capability or delay incident disability could benefit from including middle-aged adults and adding NT-proBNP and IL-6 as intermediate outcomes.

Effects of Cystatin C on Cognitive Impairment in Older Chinese Adults

OBJECTIVE

To find a suitable dividing value to classify cystatin C and evaluate the association between cognition and levels of cystatin C.

METHODS

Using data from the China Health and Retirement Longitudinal Study, We conducted a longitudinal analysis of a prospective cohort of 6,869 middle-aged and older Chinese without cognitive impairment at baseline. Levels of cystatin C were categorized into 2 groups by method of decision tree. Logistic regression models evaluated whether cystatin C was related to cognitive impairment.

RESULTS

Respondents were categorized as lower levels of cystatin C and higher levels of cystatin C, cut-point was 1.11 mg/L. Higher levels of cystatin C was associated with the odds of cognitive impairment (OR, 1.56; 95% CI, 1.10-2.22) after multivariable adjustment. Respondents with higher levels of cystatin C had worse cognition scores.

CONCLUSIONS

We found a suitable dividing value of cystatin C in middle-aged and older Chinese.

How Does Subjective Age Get "Under the Skin"? The Association Between Biomarkers and Feeling Older or Younger Than One's Age: The Health and Retirement Study

Background and Objectives

Though subjective age is a well-recognized risk factor for several chronic diseases, the biological basis for these associations remains poorly understood.

Research Design and Methods

We used new comprehensive biomarker data from the 2016 wave of the nationally representative Health and Retirement Study (HRS) to evaluate the association between biomarker levels and self-reported subjective age in a subset of 3,740 HRS participants who provided a blood sample. We measured biomarkers in seven biological domains associated with aging: inflammation, glycemia, lipids, liver function, endocrine function, renal function, and cardiac function. The primary outcome was the age discrepancy score (subjective age − chronological age) categorized as those who felt younger, older, or the same as their chronological age (reference group). Analyses adjusted for comprehensive psychosocial factors (chronic stress index, depression score), demographic factors (race, sex, body mass index, marital status, physical activity), and prevalence of chronic health conditions (comorbidity index).

Results

The prevalence of clinically relevant reduced levels of albumin concentrations was lower in those who felt younger (8.8% vs. 16.0%; p = .006) and higher in those who felt older (20.4% vs. 16.0%; p = .03) when compared with the reference category. The prevalence of clinically significant elevation in liver enzymes such as alanine aminotransferase was also significantly lower among those who felt younger (7.1% vs. 8.6%; p = .04) when compared with the reference category. Prevalence of clinically elevated levels in cystatin C was also lower among those who felt younger when compared with the reference category (50.0% vs. 59.1%; p = .04). There was no association between lipids, glucose, or C-reactive protein (inflammatory marker) and subjective age categories.

Discussion and Implications

These results suggest that people who feel younger may have favorable biomarker profiles and as a result may have lower prevalence of age-related diseases when compared with those who feel older or those who feel the same as their chronological age.

Measurement of serum cystatin C: A valuable tool for evaluating dyskinesia in Parkinson's disease

Although cystatin C (Cys C) has been implicated in the pathophysiology of Parkinson's disease (PD), whether it can be used as a tool for evaluating dyskinesia is unknown. In the present study, the association of Cys C with dyskinesia in PD patients was investigated. Fasting serum Cys C levels were measured from 120 PD patients and 156 healthy controls. Demographic information was collected for all patients. In addition, levodopa (L-dopa)-equivalent dose, Unified Parkinson's Disease Rating Scale (UPDRS) score, Hoehn and Yahr (H&Y) stage, and dyskinesia were assessed in PD patients. Receiver operating characteristic (ROC) curves were adopted to assess the evaluating accuracy of Cys C levels for distinguishing dyskinesia in PD patients. Patients with PD exhibited significantly higher serum Cys C levels compared with heathy controls. Dyskinesia was observed in 32 patients (26.7%). Multiple logistic regression showed serum Cys C levels (odds ratio, OR 12.93; 95% confidence interval, CI 1.08-54.23; p = 0.043), duration of disease (OR 1.03, 95% CI 1.01-1.05, p = 0.001) and UPDRS II score (OR 1.07, 95% CI 1.01-1.14, p = 0.019) were independently associated with dyskinesia. The ROC curve for the Cys C levels yielded a valuable accuracy for distinguishing dyskinesia in PD patients. Serum Cys C levels were independently associated with dyskinesia and may be a valuable screening tool for differentiating dyskinesia in PD patients. Although the pathophysiological mechanism of PD is complicated, the results from our study provide a better understanding of the association between Cys C and dyskinesia in PD patients and may yield insights into the pathogenesis of PD.

Correlations of serum cystatin C level and gene polymorphism with vascular cognitive impairment after acute cerebral infarction

BACKGROUND

The aim of this study was to explore the possible correlations of serum cystatin C level and cystatin C gene (CST3) polymorphism with vascular cognitive impairment in patients who had acute cerebral infarction.

METHODS

A total of 152 patients with acute cerebral infarction were recruited in this case-control study. Patients were divided into vascular cognitive impairment (VCI) group (n = 71) and cognitive impairment no dementia (CIND) group (n = 81). The serum concentrations of cystatin C were measured with immunoturbidimetric assay while the gene polymorphisms of CST3 were determined by technique polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

In the VCI group, serum cystatin C level was significantly higher than that in the control group. The frequency of the B allele was found to be higher in the VCI group as compared with that of the CIND group (18.5% vs 7.7%, p = 0.006). In logistic regression analysis, significant associations of VCI with high serum cystatin C level (OR 3.837 (1.176-12.520), p = 0.026) and CST3 B allele (OR 2.038 (1.048-3.963), p = 0.036) were also found.

CONCLUSIONS

A high cystatin C level and CST3 B allele confer risks for VCI after acute cerebral infarction. It is probable that measurement of the serum cystatin C level and detection of CST3 gene polymorphism would aid in the early diagnosis of VCI, but further studies are warranted.

Decreased cerebral blood flow and improved cognitive function in patients with end-stage renal disease after peritoneal dialysis: An arterial spin-labelling study

OBJECTIVES

The aim of this study was to evaluate the relationship between cognitive impairment and brain perfusion using arterial spin labelling (ASL) in end-stage renal disease (ESRD) patients undergoing PD.

METHODS

ESRD patients undergoing PD were recruited. Laboratory screening, neuropsychological tests and ASL magnetic resonance imaging (MRI) were conducted prior to and after 6 months of PD. Age- and sex-matched normal subjects without ESRD served as the control group. Comparisons of regional CBF between ESRD patients before or after undergoing PD and normal controls were performed. Correlations between biochemical, neuropsychological and CBF data were also conducted to evaluate the relationships.

RESULTS

ESRD patients showed poor performance in many of the neuropsychological tests; PD improved cognition in some domains. Pre-PD patients had higher mean CBF than post-PD patients and normal controls, but no significant difference was found between the normal controls and post-PD patients. Negative correlations were observed pre-PD (regional CBF in left hippocampus vs. perseverative responses, r = -0.662, p = 0.014), post-PD (mean CBF vs. haemoglobin level, r = -0.766, p = 0.002), and before and after PD (change in CBF in the left putamen vs. change in haematocrit percentage, r = -0.808, p = 0.001).

CONCLUSION

Before PD, ESRD patients had increased cerebral perfusion that was related to poorer executive function, especially in the left hippocampus. Post-PD patients performed better in some cognitive test domains than pre-PD patients. The degree of anaemia, i.e., haemoglobin level or haematocrit percentage, might predict cognitive impairment in PD patients.

KEY POINTS

• In this study, ESRD patients before PD had cerebral hyperperfusion that was related to poorer executive function. • Post-PD patients performed better in some cognitive test domains than pre-PD patients did. • The degree of anaemia might predict cognitive impairment in PD patients.

Functional capacity, renal function and vitamin D in community-dwelling oldest old

PURPOSE

The aim of this study was to evaluate the association between the decline in estimated glomerular filtration rate (eGFR) and serum 25(OH)D with the physical and mental functional capacity of elderly individuals aged 80 years or older.

METHODS

We evaluated the functional capacity in its multidomain aspects: Geriatric Depression Scale (GDS), Instrumental Activities of Daily Living (IADL), Mental State Mini-Exam (MMSE), Verbal Fluency Test (VF), handgrip strength and time to sit and rise from a chair five times, combined creatinine and cystatin C-based eGFR and 25(OH)D levels in 205 independent asymptomatic and community-dwelling elderly subjects in a cross-sectional study.

RESULTS

Every 1 year of life, there was reduction of about 10% chance of adequate performance in functional capacity. Each 1 ml/min/m² in eGFR was associated with 2% better chance of adequate performance in the IADL. We found no association between eGFR and cognition. Serum 25(OH)D between 15.00 and 22.29 ng/ml increased the chance of better performance in VF, IADL, handgrip strength and sit and rise from the chair compared to the lower level of serum vitamin D.

CONCLUSIONS

Decreased renal function associated with age compromises the ability to perform activities for independent life in the community, but we did not observe influence in specific domains of cognition and physical performance. Low serum level of 25(OH)D appears to be a marker of greater risk of functional decline than eGFR measurement in independent oldest old dwelling in the community.

Serum cystatin C, impaired kidney function, and geriatric depressive symptoms among older people living in a rural area: a population-based study

BACKGROUND

The relationship between kidney function and depressive symptoms among elderly people has been rarely investigated in settings of the general population. The aim of our study was to examine the association of serum cystatin C (cysC) and impaired kidney function with geriatric depressive symptoms among older people living in a rural community in China.

METHODS

This population-based cohort study included 1440 individuals (age ≥ 60 years) who were recruited for the Confucius Hometown Aging Project in 2010-2011; of the 1124 persons who were free of depressive symptoms, 669 (59.5%) were re-examined in 2014-2016. At baseline, data on demographics, lifestyle factors, health conditions, and medical history were collected through interviews, clinical examinations, and laboratory tests. We defined impaired kidney function as the cystatin C-based estimated glomerular filtration rate (eGFR_cysC) < 60 ml/min/1.73 m², and depressive symptoms as a score ≥ 5 on the 15-item Geriatric Depression Scale. Data were analyzed using multiple logistic and Cox proportional-hazards models.

RESULTS

Of the 1440 participants, 316 (21.9%) were defined to have geriatric depressive symptoms at baseline. Serum cysC levels of 1.01-1.25 and > 1.25 mg/L (vs. ≤1.00 mg/L) were associated with a multiple-adjusted odds ratio (OR) of 1.41 (95% CI 1.01-1.97) and 3.20 (2.32-4.41), respectively, for having geriatric depressive symptoms (P_trend < 0.001). Of the 669 people who were free of depressive symptoms at baseline, 157 had incident depressive symptoms at the follow-up examination. The multiple-adjusted hazard ratio (HR) for incident depressive symptoms were 2.16 (95% CI 1.43-3.27) for serum cysC > 1.25 mg/L (vs. < 1.00 mg/L). Impaired kidney function was cross-sectionally (multiple-adjusted OR = 2.95; 95% CI 2.22-3.92) and longitudinally (multiple-adjusted HR 1.54; 95% CI 1.03-2.30) associated with an increased risk of geriatric depressive symptoms.

CONCLUSION

Elevated serum cysC levels and impaired kidney function are associated with an increased risk of geriatric depressive symptoms among Chinese older people living in a rural community.

[Evaluation of nephrocerebral risk with the use of cystatin C in patients with chronic kidney disease]

AIM

To study a role of cystatin C in the nephrocerebral risk in chronic kidney disease at the initial stage of the disease.

MATERIAL AND METHODS

One hundred and twenty-eight patients (63 men and 65 women) with chronic kidney disease (CKD) were examined at the pre-dialysis stage of the disease. All patients underwent a complex clinical and laboratory examination with determination of the lipid spectrum, uric acid, fibrinogen, calcium and cystatin C, and subsequent calculation of the glomerular filtration rate (GFR). To assess structural changes in carotid arteries, ultrasound dopplerography was performed. Depending on the thickness of the intima-media (TIM), the entire sample is divided into CKD groups with no signs of carotid atherosclerosis (SC), n=70 and on CKD with SC, n=58.

RESULTS

Patients of the second group (CKD with SC), had higher body mass index (p<0.05), systolic (p<0.05) and central (p<0.05) arterial pressure (BP) and blood cystatin C (p<0.05). In the same group, there was a significant decrease in the concentration of high-density lipoprotein cholesterol (p<0.05) compared with those of the first group (CKD). The age of patients and the content of cystatin C (p<0.05) influenced the increase in TIM. Significant positive correlations between cystatin C content and TIM, systolic and diastolic blood pressure (p<0.05), and a negative correlation cystatin C content and GFR were noted in patients of the second group.

CONCLUSION

The increase in the level of cystatin C in blood plasma in CKD indicates the development of structural changes in the carotid arteries, the increase in the levels of systolic and central arterial pressure, the decrease in the concentration of HDL cholesterol, which is associated with significant inhibition of GFR.

Association Between Cystatin C and 20-Year Cumulative Incidence of Hearing Impairment in the Epidemiology of Hearing Loss Study

Importance

Hearing impairment (HI) is one of the most common conditions affecting older adults. Identification of factors associated with the development of HI may lead to ways to reduce the incidence of this condition.

Objective

To investigate the association between cystatin C, both as an independent biomarker and as a marker of kidney function, and the 20-year incidence of HI.

Design, Setting, and Participants

Data were obtained from the Epidemiology of Hearing Loss Study (EHLS), a longitudinal, population-based study in Beaver Dam, Wisconsin. Baseline examinations began in 1993 and continued through 1995, and participants were examined approximately every 5 years, with the most recent examination phase completed in 2015. The EHLS participants with serum cystatin C concentration data and without HI at the baseline examination were included in this study.

Main Outcomes and Measures

Participants without HI were followed up for incident HI (pure-tone average of hearing thresholds at 0.5, 1, 2, and 4 kHz >25 dB hearing level in either ear) for 20 years. Cystatin C was analyzed as a biomarker (concentration) and used to determine estimated glomerular filtration rate (eGFRCysC). Discrete-time Cox proportional hazards regression models were used to analyze the association between cystatin C concentration and eGFRCysC and the 20-year cumulative incidence of HI.

Results

There were 863 participants aged 48 to 86 years with cystatin C data and without HI at baseline. Of these, 599 (69.4%) were women. In models adjusted for age and sex, cystatin C was associated with an increased risk of developing HI (hazard ratio [HR], 1.20; 95% CI, 1.07-1.34 per 0.2-mg/L increase in cystatin C concentration), but the estimate was attenuated after further adjusting for educational level, current smoking, waist circumference, and glycated hemoglobin (HR, 1.11; 95% CI, 0.98-1.27 per 0.2-mg/L increase in cystatin C concentration). Low eGFRCysC was significantly associated with the 20-year cumulative incidence of HI in both the age- and sex-adjusted model (HR, 1.70; 95% CI, 1.16-2.48; <60 vs ≥60 mL/min/1.73 m2) and the multivariable-adjusted model (HR, 1.50; 95% CI, 1.02-2.22; <60 vs ≥60 mL/min/1.73 m2).

Conclusions and Relevance

Reduced kidney function as estimated using cystatin C, but not cystatin C alone, was associated with the 20-year cumulative incidence of HI, suggesting that some age-related HI may occur in conjunction with or as the result of reduced kidney function.

Combined measurement of plasma cystatin C and low-density lipoprotein cholesterol: A valuable tool for evaluating progressive supranuclear palsy

INTRODUCTION

Progressive supranuclear palsy (PSP) was previously thought as a cause of atypical Parkinsonism. Although Cystatin C (Cys C) and low-density cholesterol lipoprotein-C (LDL-C) are known to play critical roles in Parkinsonism, it is unknown whether they can be used as markers to distinguish PSP patients from healthy subjects and to determine disease severity.

METHODS

We conducted a cross-sectional study to determine plasma Cys C/HDL/LDL-C levels of 40 patients with PSP and 40 healthy age-matched controls. An extended battery of motor and neuropsychological tests, including the PSP-Rating Scale (PSPRS), the Non-Motor Symptoms Scale (NMSS), Geriatric Depression Scale (GDS) and Mini-Mental State Examination (MMSE), was used to evaluate the disease severity. Receiver operating characteristic (ROC) curves were adopted to assess the prognostic accuracy of Cys C/LDL-C levels in distinguishing PSP from healthy subjects.

RESULTS

Patients with PSP exhibited significantly higher plasma levels of Cys C and lower LDL-C. The levels of plasma Cys C were positively and inversely correlated with the PSPRS/NMSS and MMSE scores, respectively. The LDL-C/HDL-C ratio was positively associated with PSPRS/NMSS and GDS scores. The ROC curve for the combination of Cys C and LDL-C yielded a better accuracy for distinguishing PSP from healthy subjects than the separate curves for each parameter.

CONCLUSIONS

Plasma Cys C and LDL-C may be valuable screening tools for differentiating PSP from healthy subjects; while they could be useful for the PSP intensifies and severity evaluation. A better understanding of Cys C and LDL-C may yield insights into the pathogenesis of PSP.

Association of Kidney Function Biomarkers with Brain MRI Findings: The BRINK Study

BACKGROUND

Chronic kidney disease (CKD) studies have reported variable prevalence of brain pathologies, in part due to low inclusion of participants with moderate to severe CKD.

OBJECTIVE

To measure the association between kidney function biomarkers and brain MRI findings in CKD.

METHODS

In the BRINK (BRain IN Kidney Disease) study, MRI was used to measure gray matter volumes, cerebrovascular pathologies (white matter hyperintensity (WMH), infarctions, microhemorrhages), and microstructural changes using diffusion tensor imaging (DTI). We performed regression analyses with estimated glomerular filtration rate (eGFR) and urine albumin to creatinine ratio (UACR) as primary predictors, and joint models that included both predictors, adjusted for vascular risk factors.

RESULTS

We obtained 240 baseline MRI scans (150 CKD with eGFR <45 in ml/min/1.73 m2; 16 mild CKD: eGFR 45-59; 74 controls: eGFR≥60). Lower eGFR was associated with greater WMH burden, increased odds of cortical infarctions, and worsening diffusion changes throughout the brain. In eGFR models adjusted for UACR, only cortical infarction associations persisted. However, after adjusting for eGFR, higher UACR provided additional information related to temporal lobe atrophy, increased WMH, and whole brain microstructural changes as measured by increased DTI mean diffusivity.

CONCLUSIONS

Biomarkers of kidney disease (eGFR and UACR) were associated with MRI brain changes, even after accounting for vascular risk factors. UACR adds unique additional information to eGFR regarding brain structural and diffusion biomarkers. There was a greater impact of kidney function biomarkers on cerebrovascular pathologies and microstructural brain changes, suggesting that cerebrovascular etiology may be the primary driver of cognitive impairment in CKD.

Resveratrol supplementation confers neuroprotection in cortical brain tissue of nonhuman primates fed a high-fat/sucrose diet

Previous studies have shown positive effects of long-term resveratrol (RSV) supplementation in preventing pancreatic beta cell dysfunction, arterial stiffening and metabolic decline induced by high-fat/high-sugar (HFS) diet in nonhuman primates. Here, the analysis was extended to examine whether RSV may reduce dietary stress toxicity in the cerebral cortex of the same cohort of treated animals. Middle-aged male rhesus monkeys were fed for 2 years with HFS alone or combined with RSV, after which whole-genome microarray analysis of cerebral cortex tissue was carried out along with ELISA, immunofluorescence, and biochemical analyses to examine markers of vascular health and inflammation in the cerebral cortices. A number of genes and pathways that were differentially modulated in these dietary interventions indicated an exacerbation of neuroinflammation (e.g., oxidative stress markers, apoptosis, NF-κB activation) in HFS-fed animals and protection by RSV treatment. The decreased expression of mitochondrial aldehyde dehydrogenase 2, dysregulation in endothelial nitric oxide synthase, and reduced capillary density induced by HFS stress were rescued by RSV supplementation. Our results suggest that long-term RSV treatment confers neuroprotection against cerebral vascular dysfunction during nutrient stress.

Impact of cystatin C and microalbuminuria on cognitive impairment in the population of community-dwelling Japanese

BACKGROUND AND AIMS

Cognitive impairment is an important element affecting our well-being, and as such, early diagnosis is critical today. We investigated whether serum cystatin C and microalbuminuria are associated with cognitive impairment.

METHODS

A total of 1943 subjects (774 males, 1169 females, mean age 65.8 years) took part in the investigation, and underwent a health examination in Tanushimaru, Japan, in 2009. The participants' cognitive function was evaluated using of mini-mental state examination (MMSE). We measured the levels of serum cystatin C using latex nephelometric immunoassay. Spot urine samples were used to measure microalbuminuria levels. Multivariate linear regression analyses were used to assess the relationship between MMSE scores and the level of cystatin C or microalbuminuria. All statistical analyses were performed using the SAS system.

RESULTS

The mean values of log-transformed serum cystatin C levels and log-transformed microalbuminuria were 0.95 (range 0.41-7.11) mg/L and 10.7 (range 1.1-2600) mg/g·Cr, respectively. The means of MMSE score were 27.7 ± 2.5. In the multivariate linear regression analyses adjusted for age and sex, MMSE was significantly associated with systolic blood pressure (p = 0.024, inversely), cystatin C (p = 0.046, inversely) and microalbuminuria (p = 0.019, inversely), whereas estimated glomerular filtration rate (eGFR) had an insignificant association (p = 0.197). In the multiple stepwise linear regression analysis, age, history of stroke, systolic blood pressure, serum cystatin C were independently associated with MMSE levels.

CONCLUSIONS

We demonstrated for the first time that cognitive function was significantly and inversely associated with cystatin C and microalbuminuria, in the relatively younger general population.

Higher Cystatin C Levels Are Associated With Neurocognitive Impairment in Older HIV+ Adults

OBJECTIVE

The study aims to determine whether cystatin C is associated with HIV disease and HIV-associated neurocognitive impairment (NCI).

METHODS

Participants included 124 (HIV+ n = 77; HIV- n = 47) older adults (age ≥ 50 years) examined at the University of California, San Diego HIV Neurobehavioral Research Program. Cystatin C, a biomarker of kidney functioning that has been linked to poor health outcomes, was measured in blood. Participants completed a comprehensive neurocognitive assessment that was used to define both global and domain NCI.

RESULTS

The HIV+ group had significantly higher cystatin C concentrations than the HIV- group (d = 0.79 P < 0.001). Among HIV+ participants, those with NCI had higher cystatin C concentrations than those without NCI (d = 0.42, P = 0.055), particularly among participants taking tenofovir (d = 0.78, P = 0.004). A receiver-operator characteristic curve identified that cystatin C levels ≥0.75 mg/L were associated with NCI in the HIV+ group. Using this binary variable and including relevant covariates, multivariate modeling confirmed that NCI was associated with higher cystatin C levels (OR = 3.0; P = 0.03).

CONCLUSIONS

Our results confirm that HIV+ older adults have higher cystatin C than HIV- older adults and further identify that cystatin C may be associated with NCI in this population, particularly if they use tenofovir. This blood biomarker may be a useful clinical tool to identify older HIV+ persons at greater risk for cognitive decline.

Cognitive Impairment in Chronic Kidney Disease: Vascular Milieu and the Potential Therapeutic Role of Exercise

Chronic kidney disease (CKD) is considered a model of accelerated aging. More specifically, CKD leads to reduced physical functioning and increased frailty, increased vascular dysfunction, vascular calcification and arterial stiffness, high levels of systemic inflammation, and oxidative stress, as well as increased cognitive impairment. Increasing evidence suggests that the cognitive impairment associated with CKD may be related to cerebral small vessel disease and overall impairment in white matter integrity. The triad of poor physical function, vascular dysfunction, and cognitive impairment places patients living with CKD at an increased risk for loss of independence, poor health-related quality of life, morbidity, and mortality. The purpose of this review is to discuss the available evidence of cerebrovascular-renal axis and its interconnection with early and accelerated cognitive impairment in patients with CKD and the plausible role of exercise as a therapeutic modality. Understanding the cerebrovascular-renal axis pathophysiological link and its interconnection with physical function is important for clinicians in order to minimize the risk of loss of independence and improve quality of life in patients with CKD.