Sleep apnea prevalence in chronic kidney disease - association with total body water and symptoms

Nocturnal hypoxemic burden and micro- and macrovascular disease in patients with type 2 diabetes

BACKGROUND

Micro- and macrovascular diseases are common in patients with type 2 diabetes mellitus (T2D) and may be partly caused by nocturnal hypoxemia. The study aimed to characterize the composition of nocturnal hypoxemic burden and to assess its association with micro- and macrovascular disease in patients with T2D.

METHODS

This cross-sectional analysis includes overnight oximetry from 1247 patients with T2D enrolled in the DIACORE (DIAbetes COhoRtE) study. Night-time spent below a peripheral oxygen saturation of 90% (T90) as well as T90 associated with non-specific drifts in oxygen saturation (T90non - specific), T90 associated with acute oxygen desaturation (T90desaturation) and desaturation depths were assessed. Binary logistic regression analyses adjusted for known risk factors (age, sex, smoking status, waist-hip ratio, duration of T2D, HbA1c, pulse pressure, low-density lipoprotein, use of statins, and use of renin-angiotensin-aldosterone system inhibitors) were used to assess the associations of such parameters of hypoxemic burden with chronic kidney disease (CKD) as a manifestation of microvascular disease and a composite of cardiovascular diseases (CVD) reflecting macrovascular disease.

RESULTS

Patients with long T90 were significantly more often affected by CKD and CVD than patients with a lower hypoxemic burden (CKD 38% vs. 28%, p < 0.001; CVD 30% vs. 21%, p < 0.001). Continuous T90desaturation and desaturation depth were associated with CKD (adjusted OR 1.01 per unit, 95% CI [1.00; 1.01], p = 0.008 and OR 1.30, 95% CI [1.06; 1.61], p = 0.013, respectively) independently of other known risk factors for CKD. For CVD there was a thresholdeffect, and only severly and very severly increased T90non-specific was associated with CVD ([Q3;Q4] versus [Q1;Q2], adjusted OR 1.51, 95% CI [1.12; 2.05], p = 0.008) independently of other known risk factors for CVD.

CONCLUSION

While hypoxemic burden due to oxygen desaturations and the magnitude of desaturation depth were significantly associated with CKD, only severe hypoxemic burden due to non-specific drifts was associated with CVD. Specific types of hypoxemic burden may be related to micro- and macrovascular disease.

Sleep apnoea syndrome prevalence in chronic kidney disease and end-stage kidney disease patients: a systematic review and meta-analysis

Background

Several studies have examined the frequency of sleep apnoea (SA) in patients with chronic kidney disease (CKD), reporting different prevalence rates. Our systematic review and meta-analysis aimed to define the clinical penetrance of SA in CKD and end-stage kidney disease (ESKD) patients.

Methods

Ovid-MEDLINE and PubMed databases were explored up to 5 June 2023 to identify studies providing SA prevalence in CKD and ESKD patients assessed by different diagnostic methods, either sleep questionnaires or respiration monitoring equipment [such as polysomnography (PSG), type III portable monitors or other diagnostic tools]. Single-study data were pooled using the random-effects model. The Chi2 and Cochrane-I2 tests were used to assess the presence of heterogeneity, which was explored performing sensitivity and/or subgroup analyses.

Results

A cumulative analysis from 32 single-study data revealed a prevalence of SA of 57% [95% confidence interval (CI) 42%-71%] in the CKD population, whereas a prevalence of 49% (95% CI 47%-52%) was found pooling data from 91 studies in ESKD individuals. The prevalence of SA using instrumental sleep monitoring devices, including classical PSG and type III portable sleep monitors, was 62% (95% CI 52%-72%) and 56% (95% CI 42%-69%) in CKD and ESKD populations, respectively. Sleep questionnaires revealed a prevalence of 33% (95% CI 16%-49%) and 39% (95% CI 30%-49%).

Conclusions

SA is commonly seen in both non-dialysis CKD and ESKD patients. Sleep-related questionnaires underestimated the presence of SA in this population. This emphasizes the need to use objective diagnostic tools to identify such a syndrome in kidney disease.

Chronic intermittent hypoxia promotes glomerular hyperfiltration and potentiates hypoxia-evoked decreases in renal perfusion and PO2

Introduction: Sleep apnea (SA) is highly prevalent in patients with chronic kidney disease and may contribute to the development and/or progression of this condition. Previous studies suggest that dysregulation of renal hemodynamics and oxygen flux may play a key role in this process. The present study sought to determine how chronic intermittent hypoxia (CIH) associated with SA affects regulation of renal artery blood flow (RBF), renal microcirculatory perfusion (RP), glomerular filtration rate (GFR), and cortical and medullary tissue PO2 as well as expression of genes that could contribute to renal injury. We hypothesized that normoxic RBF and tissue PO2 would be reduced after CIH, but that GFR would be increased relative to baseline, and that RBF, RP, and tissue PO2 would be decreased to a greater extent in CIH vs. sham during exposure to intermittent asphyxia (IA, FiO2 0.10/FiCO2 0.03). Additionally, we hypothesized that gene programs promoting oxidative stress and fibrosis would be activated by CIH in renal tissue. Methods: All physiological variables were measured at baseline (FiO2 0.21) and during exposure to 10 episodes of IA (excluding GFR). Results: GFR was higher in CIH-conditioned vs. sham (p < 0.05), whereas normoxic RBF and renal tissue PO2 were significantly lower in CIH vs. sham (p < 0.05). Reductions in RBF, RP, and renal tissue PO2 during IA occurred in both groups but to a greater extent in CIH (p < 0.05). Pro-oxidative and pro-fibrotic gene programs were activated in renal tissue from CIH but not sham. Conclusion: CIH adversely affects renal hemodynamic regulation and oxygen flux during both normoxia and IA and results in changes in renal tissue gene expression.

Sleep apnea in end-stage renal disease patients: risk factors and mortality

Sleep apnea (SA) is highly prevalent in the end-stage renal disease (ESRD) population. However, the impact of SA on mortality in ESRD is unclear. This study investigates the relationship between SA and mortality in ESRD. The United States Renal Data System was queried in a retrospective cohort study to identify ESRD patients aged 18-100 years who initiated hemodialysis between 2005 and 2013. Diagnoses of SA and comorbidities were determined from International Classification of Disease-9 codes and demographic variables from Centers for Medicare and Medicaid Services Form-2728. Cox proportional hazards models were used to examine the association of SA with mortality controlling for multiple variables. Of 858,131 subjects meeting inclusion criteria, 587 were found to have central SA (CSA) and 22,724 obstructive SA (OSA). The SA cohort was younger and more likely to be male and Caucasian compared to the non-SA cohort, with more diagnoses of tobacco and alcohol use, hypertension, heart failure, and diabetes. Both CSA (adjusted hazard ratio (aHR) = 1.42, 95% confidence interval (CI): 1.29-1.56) and OSA (aHR = 1.35, 95% CI: 1.32-1.37) were associated with increased mortality. Other variables associated with increased mortality included age, dialysis initiation with a catheter or graft, alcohol use, hypertension, and cardiovascular disease. Factors associated with decreased mortality included female sex, black race, Hispanic ethnicity, diagnosis of heart failure or diabetes, and an ESRD etiology of glomerulonephritis or polycystic kidney disease. Since a diagnosis of either OSA or CSA increases mortality risk, early identification of SA and therapy in this ESRD population may improve survival.

Genetic Predisposition to a Higher Whole Body Water Mass May Increase the Risk of Atrial Fibrillation: A Mendelian Randomization Study

BACKGROUND

Observational studies have found an association between increased whole body water mass (BWM) and atrial fibrillation (AF). However, the causality has yet to be confirmed. To provide feasible protective measures on disease development, we performed Mendelian randomization (MR) design to estimate the potential causal relationship between increased BWM and AF.

METHODS

We implemented a two-sample MR study to assess whether increased BWM causally influences AF incidence. For exposure, 61 well-powered genetic instruments extracted from UK Biobank (N = 331,315) were used as the proxies of BWM. Summary genetic data of AF were obtained from FinnGen (Ncase = 22,068; Ncontrol = 116,926). Inverse-variance weighted (IVW), MR-Egger and weighted median methods were selected to infer causality, complemented with a series of sensitivity analyses. MR-Pleiotropy Residual Sum and Outlier (MR-PRESSO) and Radial MR were employed to identify outliers. Furthermore, risk factor analyses were performed to investigate the potential mechanisms between increased BWM and AF.

RESULTS

Genetic predisposition to increased BWM was demonstrated to be significantly associated with AF in the IVW model (OR = 2.23; 95% CI = 1.47-3.09; p = 1.60 × 10^-7), and the result was consistent in other MR approaches. There was no heterogeneity or pleiotropy detected in sensitivity analysis. MR-PRESSO identified no outliers with potential pleiotropy after excluding outliers by Radial MR. Furthermore, our risk factor analyses supported a positive causal effect of genetic predicted increased BWM on edematous diseases.

CONCLUSIONS

MR estimates showed that a higher BWM could increase the risk of AF. Pathological edema is an important intermediate link mediating this causal relationship.

Causal Association between Whole-Body Water Mass and Sleep Apnea: A Mendelian Randomization Study

Rationale: Growing evidence has suggested that body water content plays a critical role in sleep apnea. However, the causal relationship has not been established. Objectives: This study aimed to investigate whether increased whole-body water mass is causally associated with a higher risk of sleep apnea using two-sample Mendelian randomization (MR) analysis. Methods: Body water mass (BWM)-associated genetic instruments were extracted from a genome-wide association study conducted by Neale Lab, which incorporates 331,315 individuals of European ancestry. Genetic variants for sleep apnea were derived from the FinnGen dataset. MR analysis was performed using inverse variance-weighted and weight median methods, respectively. MR-Egger regression and MR-Pleiotropy Residual Sum and Outlier tests were applied to evaluate the directional pleiotropy. In addition, we performed a multivariable MR analysis that includes body mass index, snoring, and waist-to-hip ratio as covariate exposures to address their confounding effects. To elucidate mechanisms of the association between BWM and sleep apnea, we further conducted MR analysis on common edematous diseases. Results: MR estimates showed that per standard deviation increase in BWM led to an increase in the risk of sleep apnea by 49% (odds ratio [OR], 1.490; 95% confidence interval [CI], 1.308-1.696; P = 1.75 × 10^-9). The result after MR-Pleiotropy Residual Sum and Outlier correction further supports their causal association (OR, 1.414; 95% CI, 1.253-1.595; P = 1.76 × 10^-8). In addition, the multivariable MR analysis indicates a significant causal association between a higher BWM and increased risk of sleep apnea (OR, 1.204; 95% CI, 1.031-1.377; P = 0.036). Genetic predisposition to a higher BWM was also causally related to increased risk of edematous diseases. Conclusions: Our results suggested that increased BWM is a potential risk factor for sleep apnea. Pathologic edema is a possible intermediate factor mediating this causal association.

Is kidney a new organ target in patients with obstructive sleep apnea? Research priorities in a rapidly evolving field

The bidirectional relationship between sleep disordered breathing and chronic kidney disease (CKD) has recently gained a lot of interest. Several lines of evidence suggest the high prevalence of coexistent obstructive sleep apnea (OSA) in patients with CKD and end-stage renal disease (ESRD). In addition, OSA seems to result in loss of kidney function in some patients, especially in those with cardio-metabolic comorbidities. Treatment of CKD/ESRD and OSA can alter the natural history of each other; still better phenotyping with selection of appropriate treatment approaches is urgently needed. The aim of this narrative review is to provide an update of recent studies on epidemiological associations, pathophysiological interactions, and management of patients with OSA and CKD or ESRD.

Obstructive sleep apnea, sleep duration and chronic kidney disease in patients with coronary artery disease

BACKGROUND

Limited evidence is available addressing the potential role of sleep disorders on renal function. Here, we aimed to explore the associations of obstructive sleep apnea (OSA) and sleep duration (SD) with renal function in subjects with high cardiovascular risk.

METHODS

Consecutive subjects with coronary artery disease (CAD) underwent clinical evaluation, sleep study to define OSA and one-week wrist actigraphy to objectively measure SD. OSA was defined by an apnea-hypopnea index (AHI) of ≥15 events/hour. The estimated glomerular filtration rate (eGFR) was calculated using the CKD-EPI equation. We analyzed the associations of OSA and SD with continuous eGFR values and according to the presence of CKD (eGFR<60 mL/min/1.73 m²) after adjusting for multiple confounding factors.

RESULTS

We studied 242 subjects (62.8% men). The frequency of OSA was 55.4% and the median SD was 412.8 (363.4-457.25) min. There was no difference in the eGFRs between participants with and without OSA (69.3 ± 19.1 vs. 74.6 ± 19.3 mL/min/1.73 m², p = 0.72) and the rate of eGFR <60 mL/min/1.73 m² (34.3% vs. 25.9%; p = 0.21). Similarly, we did not find differences in patients in eGFR for those with SD ≥ 6 h versus SD < 6 h (72.5 ± 20.3 vs. 71.4 ± 19.1 mL/min/1.73 m², p = 0.72). In the linear regression analysis, AHI was independently associated with an eGFR<60 mL/min/1.73 m² in the unadjusted model [-0.15 (-0.27 to -0.04)], (P = 0.01), but not in the adjusted models. Analyses of continuous SD or the stratification in SD ≥ 6 h or <6 h also revealed neutral results on eGFR.

CONCLUSION

OSA severity and SD were not independently associated with CKD in subjects with CAD.

Prevalence of Sleep Apnea and its Associated Factors in Chronic Kidney Disease Patients

BACKGROUND

This study aimed to determine the prevalence of sleep apnea and its associated factors in patients with chronic kidney disease (CKD).

MATERIALS AND METHODS

This population-based cross-sectional study included 47 CKD patients, referred to the dialysis unit of Kosar Hospital in Semnan, Iran, in 2017. Two questionnaires were used for data collection. The first questionnaire included demographic and clinical variables, and the second questionnaire (STOP-BANG questionnaire) was used to measure sleep apnea in CKD patients. Also, the Apnea-Hypopnea Index (AHI) was calculated for all patients and was considered as the gold standard. To determine the factors associated with sleep apnea, univariate and multiple logistic regression models were used. Finally, the area under the receiver operating characteristic curve (ROC) was determined for assessing the discriminative ability of the model, as well as the accuracy of STOP-BANG questionnaire. STATA version 14 was used for data analysis.

RESULTS

The prevalence of sleep apnea in CKD patients was 53.2%. Also, its prevalence in women and men was 52% and 48%, respectively. In the multiple logistic regression model, body mass index (BMI) (OR: 1.21, 95% CI: 1.04-1.31) and blood urea nitrogen (BUN) (OR: 0.94, 95% CI: 0.91-0.98) had significant associations with sleep apnea in CKD patients; the area under the ROC curve was 0.7982 for this model. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the ROC curve of STOP-BANG questionnaire for AHI≥15 were 71.43, 61.54, 60, 72.73, and 0.6932, respectively.

CONCLUSION

This study showed that the prevalence of sleep apnea in CKD patients was high. Given the acceptable validity of STOP-BANG questionnaire, this scale can be used to screen sleep apnea in CKD patients.

Sleep Apnea in Maintenance Hemodialysis: A Mixed-Methods Study

Rationale & Objective

More than 50% of hemodialysis patients experience sleep disturbance and most have coexisting sleep apnea. However, how sleep apnea affects sleep and the overall experience of patients with chronic kidney disease treated by hemodialysis has not been evaluated.

Study Design

A mixed-methods design, incorporating cross-sectional observational and descriptive qualitative methodologies.

Setting & Participants

Patients receiving maintenance hemodialysis in Newcastle, New South Wales, Australia, with newly diagnosed sleep apnea (apnea-hypopnea index ≥ 5 per hour).

Assessments

In-laboratory polysomnography to assess sleep apnea and objective sleep parameters. Epworth Sleepiness Scale to assess daytime symptoms. A semi-structured qualitative interview to explore patient experience.

Analytical Approach

Descriptive and iterative thematic analysis.

Results

We analyzed 36 patients with newly diagnosed sleep apnea and interviewed 26 (mean age, 62 years, median apnea-hypopnea index, 32 per hour). Severity of sleep apnea did not affect patients’ sleep duration, sleep efficiency, or self-reported Epworth Sleepiness Scale score. From the qualitative interviews, 4 themes emerged: “broken sleep” related to short sleep duration, with waking and dozing off a common sleep cycle, caused by uncontrolled pain and dialysis. Many participants reported regularly “feeling unrefreshed” on waking. “Impact of sleep disturbance” included reduced physical, mental, and self-management capacity. Finally, interviewees described the need to use strategies to “soldier on” with symptoms.

Limitations

Participants’ views are only transferrable to hemodialysis patients with sleep apnea.

Conclusions

Our findings suggest that severity of sleep apnea does not affect sleep time or patient-reported daytime sleepiness; however, hemodialysis patients with sleep apnea report disturbed and unrefreshed sleep and the debilitating effects of sleep disturbance is profound. Broken and unrefreshed sleep were the dominant symptoms of sleep apnea and should be assessed routinely to identify patients with sleep apnea and improve quality of life in patients with chronic kidney disease treated with hemodialysis.

Approach and Management of Hypertension After Kidney Transplantation

Hypertension is one of the most common cardiovascular co-morbidities after successful kidney transplantation. It commonly occurs in patients with other metabolic diseases, such as diabetes mellitus, hyperlipidemia, and obesity. The pathogenesis of post-transplant hypertension is complex and is a result of the interplay between immunological and non-immunological factors. Post-transplant hypertension can be divided into immediate, early, and late post-transplant periods. This classification can help clinicians determine the etiology and provide the appropriate management for these complex patients. Volume overload from intravenous fluid administration is common during the immediate post-transplant period and commonly contributes to hypertension seen early after transplantation. Immunosuppressive medications and donor kidneys are associated with post-transplant hypertension occurring at any time point after transplantation. Transplant renal artery stenosis (TRAS) and obstructive sleep apnea (OSA) are recognized but common and treatable causes of resistant hypertension post-transplantation. During late post-transplant period, chronic renal allograft dysfunction becomes an additional cause of hypertension. As these patients develop more substantial chronic kidney disease affecting their allografts, fibroblast growth factor 23 (FGF23) increases and is associated with increased cardiovascular and all-cause mortality in kidney transplant recipients. The exact relationship between increased FGF23 and post-transplant hypertension remains poorly understood. Blood pressure (BP) targets and management involve both non-pharmacologic and pharmacologic treatment and should be individualized. Until strong evidence in the kidney transplant population exists, a BP of <130/80 mmHg is a reasonable target. Similar to complete renal denervation in non-transplant patients, bilateral native nephrectomy is another treatment option for resistant post-transplant hypertension. Native renal denervation offers promising outcomes for controlling resistant hypertension with no significant procedure-related complications. This review addresses the epidemiology, pathogenesis, and specific etiologies of post-transplant hypertension including TRAS, calcineurin inhibitor effects, OSA, and failed native kidney. The cardiovascular and survival outcomes related to post-transplant hypertension and the utility of 24-h blood pressure monitoring will be briefly discussed. Antihypertensive medications and their mechanism of actions relevant to kidney transplantation will be highlighted. A summary of guidelines from different professional societies for BP targets and antihypertensive medications as well as non-pharmacological interventions, including bilateral native nephrectomy and native renal denervation, will be reviewed.

Risk factors of sleep-disordered breathing in haemodialysis patients

Background

Sleep-disordered breathing (SDB) is common in patients with kidney disease; but often underdiagnosed as it is infrequently assessed in clinical practice. The objective of this study was to assess the risk factors of SDB in haemodialysis patients, and to identify useful assessment tools to detect SDB in this population.

Methods

We used nocturnal oximetry, Epworth Sleepiness Scale (ESS) and STOPBANG questionnaire to screen for SDB in haemodialysis patients. Presence of SDB was defined by Oxygen desaturation index (ODI≥5/h), and further confirmed by apnoea-hypopnea index (AHI) from an in-laboratory polysomnography. Blood samples were collected prior to commencing a haemodialysis treatment.

Results

SDB was detected in 70% of participants (N = 107, mean age 67 years). STOPBANG revealed that 89% of participants were at risk of SDB; however, only 17% reported daytime sleepiness on the ESS. Of the participants who underwent polysomnography (n = 36), obstructive sleep apnoea was identified in 86%, and median AHI was 34.5/h. Oximetry and AHI results were positively correlated (r = 0.62, P = 0.0001), as were oximetry and STOPBANG (r = 0.48; P<0.0001), but not ESS (r = 0.19; P = 0.08). Multivariate analysis showed that neck circumference (OR: 1.20; 95% CI: 1.07–1.34; P = 0.02) and haemoglobin (OR: 0.93; 95% CI: 0.88–0.97; P = 0.003) were independently associated with the presence of SDB.

Conclusion

Dialysis patients with a large neck circumference and anaemia are at risk of SDB; using nocturnal oximetry is practical and reliable to screen for SDB and should be considered in routine management of dialysis patients, particularly for those who demonstrate risk factors.

CKD-MBD: from the Pathogenesis to the Identification and Development of Potential Novel Therapeutic Targets

PURPOSE OF REVIEW

Although we have seen tremendous advances in the comprehension of CKD-MBD pathophysiology during the last few years, this was not accompanied by a significant change in mortality rate and quality of life. This review will address the traditional and updated pathophysiology of CKD-MBD along with the therapeutic limitations that affect CKD-MBD and proposed alternative treatment targets.

RECENT FINDINGS

An innovative concept brings the osteocyte to the center of CKD-MBD pathophysiology, in contrast to the traditional view of the skeleton as a target organ for disturbances in calcium, phosphate, parathyroid hormone, and vitamin D. Osteocytes, through the synthesis of FGF-23, sclerostin, among others, are able to interact with other organs, making bone an endocrine organ. Thus, osteocyte dysregulation might be an early event during the course of CKD. This review will revisit general concepts on the pathophysiology of CKD-MBD and discuss new perspectives for its treatment.