Increasing obstructive sleep apnea risk is associated with albuminuria in Korean adults: cross-sectional analysis

Several studies have shown an association between albuminuria and obstructive sleep apnea (OSA). However, studies on the relationship between the STOP-BANG questionnaire that can screen for OSA and microalbuminuria are still insufficient. Therefore, this study attempted to clarify the relationship between microalbuminuria and OSA risk using the STOP-BANG questionnaire in Korean adults. A total of 7478 participants (3289 men and 4189 women) aged over 40 were enrolled in the Korean National Health and Nutrition Examination Survey from 2019 to 2020. STOP-BANG questionnaire to screen OSA was obtained from subjects. The urinary albumin/creatinine ratio (ACR) and proteinuria were measured via a single dipstick to evaluate renal function. The high OSA risk group had a higher mean ACR value than the low OSA risk group (36.8 ± 172.2 vs 17.7 ± 82.5; P < 0.001). The proportion of subjects with values of 30 ≤ ACR < 300 mg/g (11.9% vs 6.1%; P < 0.001) and ACR > 300 mg/g (2.1% vs 0.7%; P < 0.001) was significantly higher in high OSA risk group. Multivariate logistic regression results confirmed that microalbuminuria (OR 1.279, 95% confidence interval (CI) 1.068-1.532, P = 0.008) was significantly correlated with high OSA risk. In addition, significant correlation with high OSA risk was also found in macroalbuminuria (OR 1.684, 95% CI 1.073-2.530, P = 0.022) and proteinuria (OR 1.355, 95% CI 1.030-1.783, P = 0.030). We confirmed a significant correlation between high OSA risk and albuminuria/proteinuria in Korean adults. Therefore, renal function evaluation is required in high OSA risk patients, and OSA diagnosis through PSG test and treatment is necessary.

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.

Anemia and Hypoxia Impact on Chronic Kidney Disease Onset and Progression: Review and Updates

Chronic kidney disease (CKD) is caused by hypoxia in the renal tissue, leading to inflammation and increased migration of pathogenic cells. Studies showed that leukocytes directly sense hypoxia and respond by initiating gene transcription, encoding the 2-integrin adhesion molecules. Moreover, other mechanisms participate in hypoxia, including anemia. CKD-associated anemia is common, which induces and worsens hypoxia, contributing to CKD progression. Anemia correction can slow CKD progression, but it should be cautiously approached. In this comprehensive review, the underlying pathophysiology mechanisms and the impact of renal tissue hypoxia and anemia in CKD onset and progression will be reviewed and discussed in detail. Searching for the latest updates in PubMed Central, Medline, PubMed database, Google Scholar, and Google search engines were conducted for original studies, including cross-sectional studies, cohort studies, clinical trials, and review articles using different keywords, phrases, and texts such as "CKD progression, anemia in CKD, CKD, anemia effect on CKD progression, anemia effect on CKD progression, and hypoxia and CKD progression". Kidney tissue hypoxia and anemia have an impact on CKD onset and progression. Hypoxia causes nephron cell death, enhancing fibrosis by increasing interstitium protein deposition, inflammatory cell activation, and apoptosis. Severe anemia correction improves life quality and may delay CKD progression. Detection and avoidance of the risk factors of hypoxia prevent recurrent acute kidney injury (AKI) and reduce the CKD rate. A better understanding of kidney hypoxia would prevent AKI and CKD and lead to new therapeutic strategies.

Sleep pattern in a group of patients undergoing hemodialysis compared to control

Background

Patients with chronic kidney disease progress regularly every year to end-stage renal disease and have to undergo dialysis. Sleep disturbances have been reported to be frequent among patients receiving dialysis and contributing to the increase of their mortality and morbidity. The present research aimed to study the sleep pattern in hemodialysis patients and the risk factors associated. This cross-sectional case-control study included 40 subjects divided into 2 groups: 20 cases recruited from Ain Shams University Hospital’s dialysis unit and 20 in the control group with normal Pittsburgh Sleep Quality Index score matched for age and sex. Both groups were subjected to overnight polysomnography, and the cases group was assessed by the Pittsburgh Sleep Quality Index to determine their sleep quality.

Results

Nearly all polysomnographic parameters were significantly abnormal in the cases group except for sleep onset latency (P > 0.05), showing obstructive sleep apnea and periodic limb movement (P value 0.001). Based on their Pittsburgh Sleep Quality Index score, 30% were classified as good sleepers and 70% as bad sleepers. On comparing both groups, a significant difference was found. Poor sleepers had more worse sleep efficiency (62.9%), spent longer time during their sleep in stage 1 (26.6%) with shorter REM onset latency (113.5 ± 99.5), and had a longer duration of illness with lower serum creatinine level compared to good sleepers.

Conclusions

The prevalence of obstructive sleep apnea and periodic limb movement in hemodialysis patients is high; patients with longer time on dialysis are at more risk of sleep disorders, whereas hemoglobin levels, BUN, and other demographic factors do not seem to play a role in sleep disorder. Hence, patients on hemodialysis need to be screened for sleep disorders so as to improve their mortality and morbidity.

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.

Fatigue in CKD: Epidemiology, Pathophysiology, and Treatment

Fatigue is a commonly reported and debilitating symptom among patients with CKD, yet little is known about its epidemiology, pathogenesis, and treatment. Various measurement tools have been used in published studies to identify and quantify fatigue. These include several single-item measures embedded in longer questionnaires for assessing depression, quality of life, or symptom burden in patients with kidney disease. Approximately 70% of patients with CKD report fatigue, with up to 25% reporting severe symptoms. Patient-reported fatigue is associated with death, dialysis initiation, and hospitalization among individuals with CKD. The pathophysiology is multifactorial and likely includes decreased oxygen delivery and increased reliance on anaerobic metabolism, thus generating lactic acidosis in response to exertion; the effects of chronic metabolic acidosis and hyperphosphatemia on skeletal muscle myocytes; protein-energy wasting and sarcopenia; and depression. Physical activity has been shown to improve fatigue in some small but promising trials, and so should be recommended, given the additional benefits of exercise. Targeting higher hemoglobin levels with erythropoiesis-stimulating agents may improve fatigue, but potential adverse cardiovascular effects preclude their use to solely treat fatigue without the presence of another indication. Current guidelines recommend cautious individualization of hemoglobin targets for those at low cardiovascular risk who still experience fatigue or functional limitation despite a hemoglobin level of 10 g/dl. Sodium bicarbonate supplementation for the treatment of metabolic acidosis may also improve functional status. Selective serotonin reuptake inhibitors have not been consistently shown to improve fatigue in patients with kidney disease, but an ongoing trial will evaluate the effect of alternative antidepressant drug and behavioral activation therapy on fatigue in patients with CKD. Overall, more research is needed to further clarify underlying mechanisms of fatigue and identify effective, targeted treatments for patients with CKD.

Sleep Apnea as a Cardiorenal Risk Factor in CKD and Renal Transplant Patients

BACKGROUND

Chronic kidney disease (CKD) is a public health priority of increasing concern worldwide. Sleep apnea (SA) of moderate-to-severe degree has a 3-9% prevalence in women and 10-17% in men in the general population.

SUMMARY

In CKD patients, the prevalence of SA parallels the decline of the GFR being 27% in CKD patients with a GFR of >60 mL/min/1.73 m2 and 57% in patients with end-stage kidney disease (ESKD). In the early CKD stages, fluid overload is probably the sole risk factor for SA in this population. At more severe CKD stages, disturbed central and peripheral chemosensitivity and the accumulation of uremic toxins might contribute to SA. Still, there is no direct evidence supporting this hypothesis in human studies. Observational studies coherently show that SA is a risk factor for CKD incidence and CKD progression as well as for cardiovascular disease and death in this population. However, there is no randomized clinical trial testing continuous positive airway pressure or other interventions documenting that attenuation of SA may have a favorable effect on renal and cardiovascular outcomes in CKD and ESKD patients. However, most likely, the causal nature of the association between SA and cardiorenal outcomes remains unproven. Renal transplantation is the most effective treatment of SA in patients with ESKD, but this disturbance re-emerges on long-term observation in this population. However, after renal transplantation, SA does not seem to be a predictor of adverse health outcomes.

Multiple, objectively measured sleep dimensions including hypoxic burden and chronic kidney disease: findings from the Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Poor sleep may contribute to chronic kidney disease (CKD) through several pathways, including hypoxia-induced systemic and intraglomerular pressure, inflammation, oxidative stress and endothelial dysfunction. However, few studies have investigated the association between multiple objectively measured sleep dimensions and CKD.

METHODS

We investigated the cross-sectional association between sleep dimensions and CKD among 1895 Multi-Ethnic Study of Atherosclerosis Sleep Ancillary Study participants who completed in-home polysomnography, wrist actigraphy and a sleep questionnaire. Using Poisson regression models with robust variance, we estimated separate prevalence ratios (PR) and 95% CIs for moderate-to-severe CKD (glomerular filtration rate <60 mL/min/1.73 m² or albuminuria >30 mg/g) among participants according to multiple sleep dimensions, including very short (≤5 hours) sleep, Apnoea-Hypopnoea Index and sleep apnoea-specific hypoxic burden (SASHB) (total area under the respiratory event-related desaturation curve divided by total sleep duration, %min/hour)). Regression models were adjusted for sociodemographic characteristics, health behaviours and clinical characteristics.

RESULTS

Of the 1895 participants, mean age was 68.2±9.1 years, 54% were women, 37% were white, 28% black, 24% Hispanic/Latino and 11% Asian. Several sleep metrics were associated with higher adjusted PR of moderate-to-severe CKD: very short versus recommended sleep duration (PR=1.40, 95% CI 1.06 to 1.83); SASHB (Box-Cox transformed SASHB: PR=1.06, 95% CI 1.02 to 1.12); and for participants in the highest quintile of SASHB plus sleep apnoea: PR=1.28, 95% CI 1.01 to 1.63.

CONCLUSIONS

Sleep apnoea associated hypoxia and very short sleep, likely representing independent biological mechanisms, were associated with a higher moderate-to-severe CKD prevalence, which highlights the potential role for novel interventions.

Interrelationship among Obstructive Sleep Apnea, Renal Function and Survival: A Cohort Study

Previous studies showed a bidirectional relationship between renal function decline and obstructive sleep apnea (OSA) syndrome. Continuous Positive Airway Pressure (C-PAP) treatment was shown to preserve the kidney function in OSA patients. This study aims to investigate the progression of long-term renal function in OSA patients treated with different PAP strategies (patients were divided into two groups, fixed C-PAP or other PAP—automatic and bilevel pressure). Comorbidities and 10-years survival were also evaluated. We performed a retrospective, observational, single-center, cohort study, including the first 40 consecutive patients enrolled from 2009 in the Respiratory disease Unit at the Vercelli University Hospital database. The patient inclusion criteria were: age ≥ 18 years with OSA syndrome according to AASM (American Academy of Sleep Medicine) guidelines. Creatinine serum levels (mg/dL) and the estimated Glomerular Filtration Rate (eGFR, mL/min calculated by CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration equation)) were measured at 3 different time points: at baseline, 3 years and 8 years after PAP treatment. The Kaplan–Meier survival curves stratified according to PAP treatment and compliance have been reported together with log-rank test estimation. In our study, we found a significant creatinine serum level reduction after 3 years of fixed C-PAP treatment (p value = 0.006) when compared to baseline values. However, we observed that the long-term C-PAP benefit was not significant (p value = 0.060). Our data confirmed the progressive renal function decline in OSA patients, especially in those using other-PAP treatments; nevertheless, OSA treatment with a fixed C-PAP device has shown, in the short term, a significant improvement in renal function. By contrast, in our study, long-term benefits after 8 years are not been demonstrated probably because of the lack of compliance of the patients and the aging effect.

Obstructive Sleep Apnea, Other Sleep Characteristics, and Risk of CKD in the Atherosclerosis Risk in Communities Sleep Heart Health Study

BACKGROUND

Obstructive sleep apnea may be associated with development of CKD through hypoxia, inflammation, and oxidative stress. Individuals with this sleep disorder are also at increased risk for established CKD risk factors, including obesity, hypertension, and type 2 diabetes.

METHODS

We examined the association between obstructive sleep apnea, other sleep characteristics, and risk of incident CKD (stage 3 or higher) in 1525 participants (mean age, 62.5 years; 52.4% women) in the Atherosclerosis Risk in Communities (ARIC) study who completed in-home polysomnography assessments. We used the apnea-hypopnea index (events per hour) to define obstructive sleep apnea severity (normal, <5.0; mild, 5.0-14.9; moderate, 15.0-29.9; and severe, ≥30.0) and defined incident CKD (stage 3 or higher) as eGFR<60 ml/min per 1.73 m² and ≥25% decline from baseline, CKD-related hospitalization or death, or ESKD. Cox proportional hazards regression was used to estimate obstructive sleep apnea severity with risk of incident CKD, adjusting for demographics, lifestyle behaviors, and cardiometabolic conditions.

RESULTS

During 19 years (median) of follow-up, 461 CKD events occurred. After adjustment for demographics and lifestyle behaviors, severe obstructive sleep apnea associated with increased risk of CKD (hazard ratio [HR], 1.51; 95% confidence interval [95% CI], 1.08 to 2.10), which was attenuated after adjustment for body mass index (HR, 1.07; 95% CI, 0.75 to 1.52). No other sleep characteristics associated with incident CKD.

CONCLUSIONS

We found a link between obstructive sleep apnea and an elevated risk of stage 3 CKD or higher, but this association was no longer significant after adjusting for obesity, a risk factor for both conditions. Given the high prevalence of obstructive sleep apnea and CKD among adults, further investigation is warranted.

Particularities of Older Patients with Obstructive Sleep Apnea and Heart Failure with Mid-Range Ejection Fraction

Background and objectives: Obstructive sleep apnea syndrome (OSAS) and heart failure (HF) are increasing in prevalence with a greater impact on the health system. The aim of this study was to assess the particularities of patients with OSAS and HF, focusing on the new class of HF with mid-range ejection fraction (HFmrEF, EF = 40%-49%), and comparing it with reduced EF (HFrEF, EF < 40%) and preserved EF (HFpEF, EF ≥ 50%). Materials and Methods: A total of 143 patients with OSAS and HF were evaluated in three sleep labs of "Victor Babes" Hospital and Cardiovascular Institute, Timisoara, Western Romania. We collected socio-demographic data, anthropometric sleep-related measurements, symptoms through sleep questionnaires and comorbidity-related data. We performed blood tests, cardio-respiratory polygraphy and echocardiographic measurements. Patients were divided into three groups depending on ejection fraction. Results: Patients with HFmrEF were older (p = 0.0358), with higher values of the highest systolic blood pressure (mmHg) (p = 0.0016), higher serum creatinine (p = 0.0013), a lower glomerular filtration rate (p = 0.0003), higher glycemic levels (p = 0.008) and a larger left atrial diameter (p = 0.0002). Regarding comorbidities, data were presented as percentage, HFrEF vs. HFmrEF vs. HFpEF. Higher prevalence of diabetes mellitus (52.9 vs. 72.7 vs. 40.2, p = 0.006), chronic kidney disease (17.6 vs. 57.6 vs. 21.5, p < 0.001), tricuspid insufficiency (76.5 vs. 84.8 vs.59.1, p = 0.018) and aortic insufficiency (35.3 vs.42.4 vs. 20.4, p = 0.038) were observed in patients with HFmrEF, whereas chronic obstructive pulmonary disease(COPD) (52.9 vs. 24.2 vs.18.3, p = 0.009), coronary artery disease(CAD) (82.4 vs. 6.7 vs. 49.5, p = 0.026), myocardial infarction (35.3 vs. 24.2 vs. 5.4, p < 0.001) and impaired parietal heart kinetics (70.6 vs. 68.8 vs. 15.2, p < 0.001) were more prevalent in patients with HFrEF. Conclusions: Patients with OSAS and HF with mid-range EF may represent a new group with increased risk of developing life-long chronic kidney disease, diabetes mellitus, tricuspid and aortic insufficiency. COPD, myocardial infarction, impaired parietal kinetics and CAD are most prevalent comorbidities in HFrEF patients but they are closer in prevalence to HFmrEF than HFpEF.

Chronic kidney disease in patients with obstructive sleep apnea. A narrative review

Prevalence of both chronic kidney disease (CKD) and obstructive sleep apnea (OSA) is continuously increasing. Moreover, the prevalence of OSA increases as kidney function declines and is higher among patients with end-stage renal disease (ESRD). In addition, OSA is recognized as a potential nontraditional risk factor for development and progression of CKD. Continuous positive airway pressure (CPAP) plays a pivotal role in the management of OSA, eliminating patients' symptoms and improving their quality of life. Recent studies suggested that CPAP treatment may have beneficial effects on kidney function among patients with OSA. This narrative review summarizes the existing knowledge on the association between CKD and OSA, with emphasis on the epidemiology, the pathophysiology of the development of CKD in OSA and vice versa, as well as the effect of CPAP on renal function.

Effect of 12-month nasal continuous positive airway pressure therapy for obstructive sleep apnea on progression of chronic kidney disease

BACKGROUND

Obstructive sleep apnea (OSA) is common among patients with chronic kidney disease (CKD). CKD may increase the risk of OSA, and OSA may increase the risk of renal injury. Nasal continuous positive airway pressure (nCPAP) is the standard treatment for OSA. However, the effect of nCPAP on the progression of CKD is unclear.

METHODS

A total of 395 patients with stage 3/4 CKD were initially examined, and 269 patients (148 non-OSA cases; 79 mild OSA cases; 42 moderate/severe OSA cases) were analyzed after implementation of the exclusion criteria. The severity of OSA was determined by polysomnography (PSG). Fifty-two OSA patients (32 mild OSA cases; 20 moderate/severe OSA cases) received nCPAP treatment for 12 months. Variables associated with OSA severity and estimated glomerular filtration rate (eGFR) were evaluated before and after the 12-month nCPAP treatment.

RESULTS

Among all 269 CKD patients, body mass index (BMI), and eGFR had significant associations with OSA severity. Age, BMI, apnea-hypopnea index (AHI), mean SaO2%, and SaO2 <90% monitoring time had independent associations with lower eGFR. The 12-month nCPAP treatment significantly reduced the rate of eGFR decline. Univariate and multivariate analysis indicated that age, BMI, AHI, mean SaO2%, and SaO2 <90% monitoring time were independently associated with reduced eGFR. Furthermore, nCPAP treatment significantly improved eGFR, AHI, mean SaO2, and SaO2 <90% monitoring time in patients with mild OSA, and improved systolic/diastolic blood pressure, urinary protein level, eGFR, AHI, mean SaO2, and SaO2 <90% monitoring time for patients with moderate/severe OSA.

CONCLUSION

This study of patients with CKD and OSA indicated that nCPAP therapy significantly ameliorated CKD progression, especially in those with moderate/severe OSA.

Fixed But Not Autoadjusting Positive Airway Pressure Attenuates the Time-dependent Decline in Glomerular Filtration Rate in Patients With OSA

BACKGROUND

The impact of treating OSA on renal function decline is controversial. Previous studies usually included small samples and did not consider specific effects of different CPAP modalities. The aim of this study was to evaluate the respective influence of fixed and autoadjusting CPAP modes on estimated glomerular filtration rate (eGFR) in a large sample of patients derived from the prospective European Sleep Apnea Database cohort.

METHODS

In patients of the European Sleep Apnea Database, eGFR prior to and after follow-up was calculated by using the Chronic Kidney Disease-Epidemiology Collaboration equation. Three study groups were investigated: untreated patients (n = 144), patients receiving fixed CPAP (fCPAP) (n = 1,178), and patients on autoadjusting CPAP (APAP) (n = 485).

RESULTS

In the whole sample, eGFR decreased over time. The rate of eGFR decline was significantly higher in the subgroup with eGFR above median (91.42 mL/min/1.73 m²) at baseline (P < .0001 for effect of baseline eGFR). This decline was attenuated or absent (P < .0001 for effect of treatment) in the subgroup of patients with OSA treated by using fCPAP. A follow-up duration exceeding the median (541 days) was associated with eGFR decline in the untreated and APAP groups but not in the fCPAP group (P < .0001 by two-way ANOVA for interaction between treatment and follow-up length). In multiple regression analysis, eGFR decline was accentuated by advanced age, female sex, cardiac failure, higher baseline eGFR, and longer follow-up duration, whereas there was a protective effect of fCPAP.

CONCLUSIONS

fCPAP but not APAP may prevent eGFR decline in OSA.

Exploring sleep disorders in patients with chronic kidney disease

Kidney disorders have been associated with a variety of sleep-related disorders. Therefore, researchers are placing greater emphasis on finding the role of chronic kidney disease (CKD) in the development of obstructive sleep apnea and restless legs syndrome. Unfortunately, the presence of other sleep-related disorders with CKDs and non-CKDs has not been investigated with the same clinical rigor. Recent studies have revealed that myriad of sleep disorders are associated with CKDs. Furthermore, there are a few non-CKD-related disorders that are associated with sleep disorders. In this narrative review, we provide a balanced view of the spectrum of sleep disorders (as identified in International Classification of Sleep disorders-3) related to different types of renal disorders prominently including but not exclusively limited to CKD.

The association of obstructive sleep apnea and renal outcomes-a systematic review and meta-analysis

BACKGROUND

The aim of this systematic review and meta-analysis was to summarize the association of obstructive sleep apnea (OSA) with renal outcome.

METHODS

Our study followed the PRISMA guidelines. Two independent reviewers searched for relevant articles in the databases of Pubmed, the Web of Science and CENTRAL, and conducted study selection and quality assessment. A random-effect model was used to estimate the effects.

RESULTS

total of 1240 articles were initially identified (Pubmed = 568, Web of Science = 640, CENTRAL = 32). After removal of duplicate articles (n = 415) and irrelevant articles (n = 788), 37 were selected for full-text review, and 18 were finally included in the analysis. Overall, patients diagnosed with OSA were found to have a higher odds ratio (OR) of a poorer renal outcome, with a pooled OR of 1.77 (95% C.I.: 1.37–2.29). The significant association between OSA and a poorer renal outcome was not affected by the medical condition of diabetes mellitus (DM). In addition, we found that OSA was consistently associated with higher albuminuria/proteinuria and a lower estimated glomerular filtration rate (eGFR), with a pooled OR of 1.84 (95% C.I.: 1.24–2.73) and 1.60 (95% C.I.: 1.19–2.16), respectively. A greater OSA severity was also found to be related to a higher OR, with a mild group OR of 1.45 (95% C.I.: 1.19–1.77) and a moderate and severe group OR of 2.39 (95% C.I.: 1.96–2.90).

CONCLUSIONS

Our study demonstrated that OSA is significantly associated with poorer renal function.

Central Sleep Apnea in Patients with Congestive Heart Failure

Central sleep apnea and Cheyne-Stokes respiration are commonly observed breathing patterns during sleep in patients with congestive heart failure. Common risk factors are male gender, older age, presence of atrial fibrillation, and daytime hypocapnia. Proposed mechanisms include augmented peripheral and central chemoreceptor sensitivity, which increase ventilator instability during both wakefulness and sleep; diminished cerebrovascular reactivity and increased circulation time, which impair the normal buffering of Paco₂ and hydrogen ions and delay the detection of changes in Paco₂ during sleep; and rostral fluid shifts that predispose to hypocapnia.

The Triad of Sleep Apnea, Hypertension, and Chronic Kidney Disease: A Spectrum of Common Pathology

Obstructive sleep apnea (OSA), hypertension, and chronic kidney disease (CKD) are different entities and are generally managed individually most of the time. However, CKD, OSA, and hypertension share many common risk factors and it is not uncommon to see this complex triad together. In fact, they share similar pathophysiology and have been interlinked with each other. The common pathophysiology includes chronic volume overload, hyperaldosteronism, increased sympathetic activity, endothelial dysfunction, and increased inflammatory markers. The combination of this triad has significant negative impact on the cardiovascular health, and increases the mortality and morbidity in this complicated group of patients. On one hand, progression of CKD can lead to the worsening of OSA and hypertension; similarly, worsening sleep apnea can make the hypertension difficult to treat and enhance the progression of CKD. This review article highlights the bidirectional interlink among these apparently different disease processes which share common pathophysiological mechanisms and emphasizes the importance of treating them collectively to improve outcomes.

A systematic review of sleep disorders in patients with chronic kidney disease undergoing hemodialysis

The purpose of this study was to conduct a systematic review of the available evidence on sleep disorders in patients with end stage renal disease (ESRD) undergoing hemodialysis (HD). [Subjects and Methods] Two independent reviewers performed a computer-assisted search of the MEDLINE, SciELO, LILACS, and BIREME Virtual Health Library medical databases from their inception to November 2015. [Results] One thousand one hundred twenty-six articles were found that met the inclusion criteria. Articles were excluded if they were not in English, the patients did not undergo HD, or the studies were not cross-sectional or clinical trials. After reading the full text, a further 300 studies were excluded because they did not use polysomnography. The remaining 18 studies with ESRD patients undergoing HD comprised 8 clinical trials and 10 cross-sectional studies. This systematic review followed the criteria outlined by the PRISMA declaration. [Conclusion] In this systematic review, a high prevalence of sleep disorders was observed in ESRD, including sleep-disordered breathing. This knowledge may enable health professionals to devise new strategies for the diagnosis and treatment of these patients, in order to reduce morbidity and mortality and improve their quality of life.

Central Sleep Apnea in Kidney Disease

Sleep is an essential function of life and serves a crucial role in the promotion of health and performance. Poor sleep quality and sleep disorders have been a recurrent finding in patients with chronic kidney disease (CKD). Sleep disorders such as obstructive sleep apnea (OSA) can contribute to hypertension, diabetes, cardiovascular disease, and worsen obesity, all of which are implicated in the etiology of CKD, but CKD itself may lead to OSA. Relationships between CKD/end-stage renal disease (ESRD) and OSA have been the subject of numerous investigations, but central sleep apnea (CSA) also is highly prevalent in CKD/ESRD but remains poorly understood, underdiagnosed, and undertreated in these patients. Emerging literature has implicated CSA as another contributor to morbidity and mortality in CKD/ESRD, and several studies have suggested that CSA treatment is beneficial in improving these outcomes. Patients with CKD/ESRD co-existing with congestive heart failure are particularly prone to CSA, and studies focused on managing CSA in congestive heart failure patients have provided important information concerning how best to manage CSA in kidney disease as well. Adaptive servo-ventilation ultimately may represent the treatment of choice in these patients, although a stepped approach using a variety of therapeutic modalities is recommended.

Chronic Obstructive Pulmonary Disease is associated with risk of Chronic Kidney Disease: A Nationwide Case-Cohort Study

Patients with chronic obstructive pulmonary disease (COPD) and chronic kidney disease (CKD) share common risk factors. However, there is limited information about COPD and CKD. This is case-cohort study was carried out using the Taiwanese National Health Insurance Research Database to evaluate the correlation between COPD and CKD. We identified cases aged older than 40 years who had an inpatient hospitalization with a first-time COPD diagnosis between 1998 and 2008. Control were selected from hospitalized patients without COPD or CKD and were matched according to age, gender, and year of admission at a 2:1 ratio. Cox proportional hazards model was used to assess the association of CKD and COPD. The overall incidence of CKD was higher in the COPD group (470.9 per 10⁴ person-years) than in the non-COPD group (287.52 per 10⁴ person-years). The adjusted hazard ratio of case was 1.61 (P < 0.0001) times that of control. COPD was found to be associated with kidney disease from our follow-up. To detect CKD early, early diagnosis of CKD in patients with COPD and prompt initiation of monitoring and treatment are imperative.

Adiponectin protects the kidney against chronic intermittent hypoxia-induced injury through inhibiting endoplasmic reticulum stress

PURPOSE

The current study was carried out to assess the effects of chronic intermittent hypoxia (CIH) on the kidney, the intervention roles of adiponectin (Ad), and the associated mechanisms.

METHODS

Sixty Wistar rats were randomly divided into four groups: the normal control (NC), normal control plus Ad supplement (NC + Ad), CIH, and CIH plus Ad supplement (CIH + Ad) groups. The rats in both CIH and CIH + Ad groups were submitted to a CIH environment for 4 months, while the rats in NC and NC + Ad groups were housed with the normal air for 4 months. In addition, the rats in NC + Ad and CIH + Ad groups were treated with an intravenous injection of Ad at a dosage of 10 μg per injection, twice a week, for four successive months.

RESULTS

The production level of reactive oxygen species (ROS) and the protein levels of endoplasmic reticulum (ER) stress, as well as the cell apoptosis level in kidney, were all higher in the CIH group than in the NC and NC + Ad groups (all p < 0.05). However, the ROS production, the protein of ER stress, and cell apoptosis levels in kidney were all lower in the CIH + Ad group than those in the CIH group (all p < 0.05).

CONCLUSION

Ad could protect against CIH-induced renal cell apoptosis through inhibiting ROS-related ER stress.

Hypoxia: The Force that Drives Chronic Kidney Disease

In the United States the prevalence of end-stage renal disease (ESRD) reached epidemic proportions in 2012 with over 600,000 patients being treated. The rates of ESRD among the elderly are disproportionally high. Consequently, as life expectancy increases and the baby-boom generation reaches retirement age, the already heavy burden imposed by ESRD on the US health care system is set to increase dramatically. ESRD represents the terminal stage of chronic kidney disease (CKD). A large body of evidence indicating that CKD is driven by renal tissue hypoxia has led to the development of therapeutic strategies that increase kidney oxygenation and the contention that chronic hypoxia is the final common pathway to end-stage renal failure. Numerous studies have demonstrated that one of the most potent means by which hypoxic conditions within the kidney produce CKD is by inducing a sustained inflammatory attack by infiltrating leukocytes. Indispensable to this attack is the acquisition by leukocytes of an adhesive phenotype. It was thought that this process resulted exclusively from leukocytes responding to cytokines released from ischemic renal endothelium. However, recently it has been demonstrated that leukocytes also become activated independent of the hypoxic response of endothelial cells. It was found that this endothelium-independent mechanism involves leukocytes directly sensing hypoxia and responding by transcriptional induction of the genes that encode the β2-integrin family of adhesion molecules. This induction likely maintains the long-term inflammation by which hypoxia drives the pathogenesis of CKD. Consequently, targeting these transcriptional mechanisms would appear to represent a promising new therapeutic strategy.

Sleep apnea syndrome and restless legs syndrome in kidney transplant recipients

Background:

This study was aimed to evaluate the prevalence of obstructive sleep apnea (OSA) and restless legs syndrome (RLS) in patients with end-stage renal disease (ESRD) after kidney transplantation.

Materials and Methods:

Two hundred kidney transplant recipients were enrolled in this cross-sectional study. Data on age, gender, etiology of ESRD, history of previous kidney transplantation, serum creatinine, and the presence or absence of OSA and RLS were collected. Symptoms of RLS were identified using the RLS questionnaire which was completed by the patients. The Berlin questionnaire and polysomnography were used for diagnosing OSA.

Results:

The mean age of the studied patients was 45.86 ± 10.24 years. The prevalence of OSA was 26% (52 of 200 studied patients) and of RLS was 51.5% (103 of 200 studied patients). Majority of the patients with high-risk OSA were male and significantly older than the patients with low-risk OSA (P < 0.05). The prevalence of RLS was higher in patients with high-risk OSA and a higher level of creatinine compared to that in those with a low risk of OSA (P < 0.0001). Level of creatinine in patients with positive RLS was significantly higher than in those with negative RLS (P < 0.0001). OSA was observed in almost 42% of patients with positive RLS, compared to 9% of patients with negative RLS (P < 0.0001).

Conclusion:

In summary, our results indicate that the prevalence of OSA and RLS in kidney transplant recipients was higher than in the general population. Also, there was a significant association between OSA and RLS in these patients.

Obstructive Sleep Apnea and Kidney Disease: A Potential Bidirectional Relationship?

Chronic kidney disease (CKD) is associated with high mortality rates and heavy economic and social burdens. Nearly 10% of the United States population suffer from CKD, with fatal outcomes increased by 16-40 times even before reaching end-stage renal disease. The prevalence of obstructive sleep apnea (OSA) is between 3% and 7% in the general population, and has increased dramatically during the last 2 decades along with increased rates of obesity. However, the prevalence of OSA is much greater in patients with CKD. In addition, aggressive dialysis improves OSA. The current literature suggests a bidirectional association between CKD and OSA through a number of potential pathological mechanisms, which increase the possibility of both diseases being possible risk factors for each other. CKD may lead to OSA through a variety of mechanisms, including alterations in chemoreflex responsiveness, pharyngeal narrowing due to fluid overload, and accumulation of uremic toxins. It is also being increasingly recognized that OSA can also accelerate loss of kidney function. Moreover, animals exposed to intermittent hypoxia suffer histopathological renal damage. Potential mechanisms of OSA-associated renal dysfunction include renal hypoxia, hypertension, endothelial dysfunction, activation of the sympathetic nervous system, and increased oxidative stress.

Sleep apnea and the risk of chronic kidney disease: a nationwide population-based cohort study

STUDY OBJECTIVES

Sleep apnea (SA) is characterized by apnea during sleep and is associated with cardiovascular diseases and an increase in all-cause mortality. Chronic kidney disease (CKD) is a global health problem that has placed a substantial burden on healthcare resources. However, the relationship between SA and the incidence of CKD is not clear. This study aimed to determine whether SA is an independent risk factor for the development of CKD.

DESIGN

Retrospective cohort study.

SETTING

National Health Insurance Research Database (NHIRD) of Taiwan.

PATIENTS OR PARTICIPANTS

A total of 4,674 adult patients (age ≥ 30 y) in whom SA was newly diagnosed from 2000 to 2010 were included, together with 23,370 non-SA patients as the comparison group. The two groups were frequency-matched for sex, age, and year of receiving medical service. Each individual was followed until 2011.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

These two groups were monitored and observed for the occurrence of CKD. Patients with SA experienced a 1.94-fold increase (95% confidence interval [CI], 1.52-2.46; P < 0.001) in the incidence of CKD, which was independent of sex, age, and comorbid medical conditions. Additionally, they showed a 2.2-fold increase (95% CI, 1.31-3.69; P < 0.01) in the incidence of end-stage renal disease (ESRD).

CONCLUSIONS

Patients with sleep apnea are at increased risk for chronic kidney disease and end-stage renal disease compared with the general population. As such, screening renal function and treatment of chronic kidney disease is an important issue in patients with sleep apnea.

Sleep apnea and the kidney: is sleep apnea a risk factor for chronic kidney disease?

The prevalence of chronic kidney disease (CKD) is increasing, which presents challenges for both patients and health-care budgets. Although this phenomenon has been attributed to the growth in diabetes, hypertension, and obesity, sleep apnea and nocturnal hypoxemia may also contribute to the pathogenesis of CKD and its progression to kidney failure. Two pathophysiologic mechanisms responsible for CKD are glomerular hyperfiltration and chronic intrarenal hypoxia, resulting in tubulointerstitial injury, the final common pathway to end-stage kidney disease (ESKD). Multiple descriptive studies have demonstrated an association between CKD and sleep apnea. Although sleep apnea is common in patients with CKD and associated with significant nocturnal hypoxemia, it is often relatively free of sleep-related symptoms, making it difficult to detect without objective nocturnal monitoring. Nevertheless, sleep apnea and nocturnal hypoxemia have been associated with loss of kidney function and kidney injury, suggesting that they contribute to the pathogenesis of continued deterioration in kidney function. There are several pathways through which sleep apnea may achieve this, including a direct effect of intrarenal hypoxia and activation of the systemic and renal renin-angiotensin system. Further research is required to better understand these relationships and determine whether specific interventions in patients with sleep apnea have an impact on clinical outcomes, such as reducing the prevalence of CKD and delaying its progression to ESKD.

Sleep disturbances as nontraditional risk factors for development and progression of CKD: review of the evidence

Despite the high prevalence and enormous public health implications of chronic kidney disease (CKD), the factors responsible for its development and progression are incompletely understood. To date, only a few studies have attempted to objectively characterize sleep in patients with CKD prior to kidney failure, but emerging evidence suggests a high prevalence of sleep disorders, particularly obstructive sleep apnea. Laboratory and epidemiologic studies have shown that insufficient sleep and poor sleep quality promote the development and exacerbate the severity of 3 important risk factors for CKD, namely hypertension, type 2 diabetes, and obesity. In addition, sleep disturbances might have a direct effect on CKD through chronobiological alterations in the renin-angiotensin-aldosterone system and sympathetic nervous system activation. The negative impact of sleep disorders on vascular compliance and endothelial function also may have a deleterious effect on CKD. Sleep disturbances therefore may represent a novel risk factor for the development and progression of CKD. Optimizing sleep duration and quality and treating sleep disorders may reduce the severity and delay the progression of CKD.

Resistant hypertension and obstructive sleep apnea in the setting of kidney disease

OBJECTIVES

To explore the relationship between obstructive sleep apnea (OSA) and resistant hypertension in chronic kidney disease (CKD) and end-stage renal disease (ESRD).

METHODS

We examined sleep parameters and blood pressure (BP) in 224 community-based, non-CKD participants from the Sleep-SCORE study: 88 nondialysis-dependent CKD and 95 ESRD participants. Unattended home polysomnography with standardized scoring protocols and automated BP monitors were used. Resistant hypertension was defined as a BP of at least 140/90  mmHg despite at least three antihypertensive drugs.

RESULTS

Mean SBP of the CKD and ESRD groups were significantly higher than that of the non-CKD group [148.2 (23.8), 144.5 (26.7) vs. 132.2  mmHg (26.7), respectively; P < 0.0001] despite the use of more antihypertensive medications. The CKD and ESRD groups had higher rates of resistant hypertension than the non-CKD group (41.4, 22.6 vs. 6.7%, respectively; P < 0.0001). The severity of sleep apnea was associated with a higher risk of resistant hypertension. Although resistant hypertension was associated with severe sleep apnea in participants with ESRD [odds ratio (OR) 7.1, 95% confidence interval (CI) 2.2-23.2), there was no significant association in the non-CKD (OR 3.5, 95% CI 0.8-15.4) or CKD groups (OR 1.2, 95% CI 0.4-3.7) after accounting for case-mix.

CONCLUSION

The association between resistant hypertension and sleep apnea appeared robust in ESRD. OSA may contribute to resistant hypertension or both may be linked to a common underlying process such as volume excess. Future studies in patients with kidney disease should further characterize the resistant hypertension-OSA relationship and determine whether treatment of underlying mechanisms may improve outcomes.

Comment accompanying: obstructive sleep apnoea: a stand-alone risk factor for chronic kidney disease by Chou Yu-Ting

Sleep apnoea (SA) is a high priority health problem because it disrupts sleep and reduces quality of life, it is associated with obesity, hypertension, especially resistant hypertension, congestive heart failure, diabetes and it engenders cardiovascular (CV) complications and death. The following types of apnoea can be distinguished: (i) obstructive, (ii) central (i.e. neurally mediated) and (iii) mixed. Obstructive SA (OSA) is characterized by a cessation of airflow caused by occlusion of the oropharyngeal tract and central SA by a transient abolition of the neural drive to respiratory muscles. Mixed apnoea represents a combination of the two forms. SA is one of the most important triggers of high sympathetic activity and it is perhaps the most important non-traditional risk factor underlying the high CV risk of chronic kidney disease (CKD). The high sympathetic activity engenders three intermediate mechanisms, chronic hypertension, left ventricular hypertrophy and arrhythmias, particularly atrial fibrillation, which eventually leads to CV complications and death. SA is common in end-stage renal disease and studies in haemodialysis and peritoneal dialysis patients coherently show that intensive dialysis improves SA in patients with severe sleep disordered breathing. Renal transplantation is in theory the ideal way of correcting SA, because a restored renal function abrogates the uraemic toxicity. In a case-control study, the prevalence of mild and severe SA was almost identical in renal transplant patients as compared to age-, sex- and body mass index-matched healthy subjects, supporting the contention that renal transplantation reverses SA. A study published in this issue of Nephrology, Dialysis Transplantation assesses the association between CKD and SA in symptomatic (snorers) patients, excluding by protocol those with hypertension and diabetes, which are well-known risk factors for SA and CKD. The primary hypothesis tested in this study, i.e. whether snorers are at a higher risk for renal dysfunction, is a sensible one.

Obstructive sleep apnea: a stand-alone risk factor for chronic kidney disease

BACKGROUND

Previous studies have found an association between obstructive sleep apnea (OSA) and chronic kidney disease (CKD). However, subjects with confounding factors such as diabetes and hypertension were not excluded. The purpose of the present study was to determine whether patients with OSA without meeting criteria for diabetes or hypertension would also show increased likelihood of CKD.

METHODS

We prospectively enrolled adult patients with a chief complaint of habitual snoring. Overnight polysomnography, fasting blood triglyceride, cholesterol, glucose, insulin, creatinine, albumin and hemoglobin A1c, and first voiding urine albumin and creatinine were examined. Estimated glomerular filtration rate (eGFR), urine albumin-to-creatinine ratio (UACR), homeostatic model assessment-insulin resistance and percentage of CKD were calculated.

RESULTS

The final analyses involved 40 patients who were middle-aged [44.8 (8.6) years] predominantly male (83%), obese [body mass index, 28.2 (5.1) kg/m(2)] and more severe OSA, with an apnea-hypopnea index (AHI) of 51.6 (39.2)/h. The mean eGFR and UACR were 85.4 (18.3) mL/min/1.73m(2) and 13.4 (23.4) mg/g, respectively. The prevalence of CKD in severe OSA subjects is 18%. With stepwise multivariate linear regression analysis, AHI and desaturation index were the only independent predictor of UACR (β = 0.26, P = 0.01, R(2) = 0.17) and eGFR (β = 0.32, P < 0.01, R(2) = 0.32), respectively.

CONCLUSIONS

High prevalence of CKD is present in severe OSA patients without hypertension or diabetes. Significantly positive correlations were found between severity of OSA and renal function impairment.

The impact of obstructive sleep apnea on chronic kidney disease

Obstructive sleep apnea (OSA) is an important clinical problem in the chronic kidney disease (CKD) population. OSA is associated with hypoxemia and sleep fragmentation, which activates the sympathetic nervous system, the renin-angiotensin-aldosterone system, alters cardiovascular hemodynamics, and results in free radical generation. In turn, a variety of deleterious processes such as endothelial dysfunction, inflammation, platelet aggregation, atherosclerosis, and fibrosis are triggered, predisposing individuals to adverse cardiovascular events and likely renal damage. Independent of obesity, OSA is associated with glomerular hyperfiltration and may be an independent predictor of proteinuria, a risk factor for CKD progression. OSA is also associated with hypertension, another important risk factor for CKD progression, particularly proteinuric CKD. OSA may mediate renal damage via several mechanisms, and there is a need to better elucidate the impact of OSA on incident renal disease and CKD progression.

The suffocating kidney: tubulointerstitial hypoxia in end-stage renal disease

Chronic kidney disease (CKD) is characterized by irreversible pathological processes that result in the development of end-stage renal disease (ESRD). Accumulating evidence has emphasized the important role of chronic hypoxia in the tubulointerstitium in the final common pathway that leads to development of ESRD. The causes of chronic hypoxia in the tubulointerstitium are multifactorial and include mechanisms such as hemodynamic changes and disturbed oxygen metabolism of resident kidney cells. Epidemiological studies have revealed an association between CKD and systemically hypoxic conditions, such as chronic obstructive pulmonary disease and sleep apnea syndrome. In addition to tubulointerstitial hypoxia, glomerular hypoxia can occur and is a crucial factor in the development of glomerular disorders. Chemical compounds, polarographic sensors, and radiographical methods can be used to detect hypoxia. Therapeutic approaches that target chronic hypoxia in the kidney should be effective against a broad range of kidney diseases. Amelioration of hypoxia is one mechanism of inhibiting the renin-angiotensin system, the current gold standard of CKD therapy. Future therapeutic approaches include protection of the vascular endothelium and appropriate activation of hypoxia-inducible factor, a key transcription factor involved in adaptive responses against hypoxia.