Sleep-disordered breathing in nondialyzed patients with chronic renal failure

Sleep disorders in chronic kidney disease

Sleep disorders are highly prevalent in chronic kidney disease (CKD) but are often under-recognized. Restless legs syndrome, which is common in CKD owing to issues with dopamine metabolism and is exacerbated by iron deficiency and uraemia, can lead to poor sleep quality and increased daytime fatigue. Insomnia is also prevalent in CKD, particularly in patients requiring dialysis, with increased sleep latency and sleep fragmentation being reported. The cause of insomnia in CKD is multifactorial - poor sleep habits and frequent napping during dialysis, uraemia, medications and mood disorders have all been suggested as potential contributing factors. Sleep apnoea and CKD are also now recognized as having a bi-directional relationship. Sleep apnoea is a risk factor for accelerated progression of CKD, and fluid overload, which is associated with kidney failure, can lead to both obstructive and central sleep apnoea. The presence of obstructive sleep apnoea in CKD can exacerbate the already heightened cardiovascular morbidity and mortality in these patients, as well as leading to daytime fatigue and reduced quality of life. Increased awareness, timely diagnosis and appropriate therapeutic interventions are essential to reduce the negative impact of sleep disorders in patients with kidney 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.

Prevalence of obstructive sleep apnea in patients with chronic kidney disease: a hospital-based study

BACKGROUND

Chronic kidney disease (CKD) is has been rising over the past few years, and obstructive sleep apnea (OSA) is a prevalent comorbidity in this population.

AIM

To determine the prevalence of OSA in patients with chronic kidney disease stages I-V and end-stage renal disease (ESRD).

METHODS

Patients with CKD of varying grades and ESRD routinely visiting outpatient nephrology clinic or admitted in department of nephrology were included in the study. Stages I-III were categorized as early stages of CKD and stages IV-V and ESRD as late stages of CKD. Patients were categorized into a high risk group based on STOP-BANG and Berlin questionnaires. Patients who were high risk were subjected to in-hospital overnight level III polysomnography. Student's independent t-test and analysis of variance (ANOVA) were employed for the comparison of continuous variables. Chi-square test and Fisher's exact test, as appropriate, were used for the comparison of categorical variables.

RESULTS

Of 111 patients, 46 (41%) were found to have OSA. Of these patients, 15 (33%) had mild OSA (AHI 5-14/h), 13 (28%) had moderate OSA (15-29/h), and 18 (39%) had severe OSA (AHI ≥ 30/h). Overall, 31% of patients in the early stage of CKD and 45% in the late stage were found to have OSA.

CONCLUSION

This study demonstrated a high prevalence of OSA in patients with CKD when compared to the general population affecting both genders equally. The risk of OSA was higher in the advanced stages of CKD compared to the early stages, and dialysis had no effect on prevalence. Since OSA increases the cardiovascular morbidity in CKD the leading cause of death in these patients, early diagnosis and treatment of OSA may have promise to affect the mortality.

History of Sleep Disorders in Chronic Kidney Disease: First Approach

OBJECTIVES

In this study, we examined the history of sleep disorders in chronic kidney disease, 60 years after the advent of hemodialysis and renal transplant of genetically nonrelated organs, which have spurred a critical mass of data.

MATERIALS AND METHODS

We analyzed selected literature on sleep disorders in chronic kidney disease from 1959 onward.

RESULTS

Sleep disturbances are present in the general population. They cause loss of renal function and progressive nephron loss. Insomnia, sleep apnea, restless leg syndrome, and periodic limb movements represent sleep disturbances in chronic kidney disease. These symptoms manifest early in chronic kidney disease and are a rule in patients on dialysis and kidney transplant recipients. Sleep disturbances cause fatigue, excessive daily sleepiness, impaired daytime function, impaired health-related quality of life, increased morbidity, and increased mortality.

CONCLUSIONS

Sleep disorders affect most patients with chronic kidney disease. No ascertained pharmacological therapy exists, and even a successful transplant does not totally restore a refreshing sleep. Longer nocturnal hemodialysis is of benefit. Sleep apnea may be cured with continuous positive airway pressure.

Restless Legs Syndrome in Chronic Kidney Disease- a Systematic Review

Objectives

The objective of this review is to provide updated information on the epidemiology, correlating factors and treatment of chronic kidney disease associated restless legs syndrome (CKD-A-RLS) in both adult and pediatric population.

Materials and Methods

We have reviewed the Medline search and Google Scholar search up to May 2022, using key words restless legs syndrome, chronic kidney disease and hemodialysis and kidney transplant. The reviewed articles were studied for epidemiology, correlating factors, as well as pharmacologic and non-pharmacologic treatment options.

Results

Our search revealed 175 articles, 111 were clinical trials or cross- sectional studies and 64 were review articles. All 111 articles were retrieved and studied in detail. Of these, 105 focused on adults and 6 on children. A majority of studies on dialysis patients reported a prevalence between 15-30%, which is notably higher than prevalence of RLS in general population (5-10%). The correlation between presence of CKD-A-RLS with age, gender, abnormalities of hemogram, iron, ferritin, serum lipids, electrolytes and parathyroid hormones were also reviewed. The results were inconsistent and controversial. Limited studies have reported on the treatment of CKD-A-RLS. Non-pharmacological treatment focused on the effect(s) of exercise, acupuncture, massage with different oils and infra-red light whereas, pharmacologic treatment options include the effects of dopaminergic drugs, Alpha2-Delta ligands (gabapentin and pregabalin), vitamins E and C, and intravenous iron infusion.

Conclusion

This updated review showed that RLS is two to three times more common in patients with CKD compared to the general population. More patients with CKD-A-RLS demonstrated increased mortality, increased incidence of cardiovascular accident, depression, insomnia and impaired quality of life than those with CKD without RLS. Dopaminergic drugs such as levodopa, ropinirole, pramipexole and rotigotine as well as calcium channel blockers (gabapentin and pregabalin) are helpful for treatment of RLS. High quality studies with these agents are currently underway and hopefully confirm the efficacy and practicality of using these drugs in CKD-A-RLS. Some studies have shown that aerobic exercise and massage with lavender oil can improve symptoms of CKD-A- RLS suggesting that these measures can be useful as adjunct therapy.

Mortality and Cardiovascular Events in Patients With Chronic Kidney Disease and Sleep Apnea Syndrome

Background

The incidence of sleep apnea syndrome (SAS) is reported to be markedly high in patients with chronic kidney disease (CKD). Therefore, it is extremely important to know whether SAS affects prognosis in patients with CKD. Further, it is imperative to understand the prognostic impact of home continuous positive airway pressure (CPAP) therapy, which is one of the most common treatments for SAS.

Materials and Methods

We used a clinical database to identify patients with CKD using diagnosis codes. We included patients with CKD aged 20 years or more, not on renal replacement therapy, with a known change in renal function for at least 1 year. The propensity score was used to compare event rates for patients with SAS and those without SAS. In addition, the prognostic impact of CPAP therapy was investigated. The primary outcome is a composite of death, initiation of renal replacement therapy, hospitalization for heart failure, ischemic heart disease, and cerebrovascular disease.

Results

From the database, 31,294 patients with CKD without SAS and 1,026 with SAS were found to be eligible. Of these, 419 (41%) patients with SAS and 10,713 (34%) patients without SAS (P < 0.01) reached the primary outcome. After adjustment with the propensity score, the SAS group was found to have a similarly poor prognosis (P < 0.01): the hazard ratio for the primary outcome was 1.26 (95% CI, 1.08–1.45, P < 0.01) in the group with SAS compared with the group without SAS. Conversely, in patients with SAS and using CPAP, the hazard ratio was lower and did not differ significantly (HR 0.96, 95% CI: 0.76–1.22, P = 0.76).

Conclusion

In patients with CKD and SAS, the risk of death and cardiovascular disease is high. In addition, patients treated with CPAP may have improved life expectancy.

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.

Prevalence and correlates of sleep apnea among US Veterans with chronic kidney disease

The prevalence and correlates of sleep apnea (SA) among Veterans with chronic kidney disease (CKD), a population at high risk of both SA and CKD, are unknown. We performed a cross-sectional analysis of 248 Veterans (18-89 years) selected only for presence of moderate to severe CKD. All participants underwent full, unattended polysomnography, measurement of renal function and a sleepiness questionnaire. Logistic regression with backward selection was used to identify predictors of prevalent SA (apnea-hypopnea index [AHI, ≥15 events/hr] and prevalent nocturnal hypoxia [NH, % of total sleep time spent at <90% oxygen saturation]). The mean age of our cohort was 73.2 ± 9.6 years, 95% were male, 78% were Caucasian and the mean body mass index (BMI) was 30.3 ± 4.8 kg/m² . The prevalence of SA was 39%. There was no difference in daytime sleepiness among those with and without SA. In the final model, older age, higher BMI and diabetes mellitus (DM) were associated with higher odds of SA, after controlling for age, BMI, race and sex. Higher BMI, DM, unemployed/retired status, current smoking and higher serum bicarbonate level were associated with prevalent NH. To sum, SA was common among Veterans with moderate to severe CKD. Although some traditional risk factors for SA were associated with SA in this population, sleepiness did not correlate with SA. Further study is needed to validate our findings and understand how best to address the high burden of SA among Veterans with CKD.

Cardiometabolic correlates of sleep-disordered breathing in renal transplant children

Sleep-disordered breathing, a prevalent condition among adult renal transplant (RTx) recipients, has become an established independent risk factor of MetS, and furthermore, it might contribute to increased CV risk. Despite the proven correlations in adults, there is a lack of evidence for its significance in the pediatric RTx population. In this study, we aimed at assessing the prevalence and the clinical correlates of SDB in RTx children. Data of 13 patients (age [mean ± SD]: 14.2 ± 2.7 years) were analyzed. SDB was evaluated by PSG, as severity score OAHI was applied. Carbohydrate metabolism was characterized by OGTT, whereas CV status was studied by ABPM. Three composite end-points were calculated as sum of z-scores: daytime systolic and diastolic BP; nighttime systolic and diastolic BP; and glucose and insulin levels at 120 minutes. Eight patients (61.5%) were diagnosed with SDB of whom five patients (38.5%) had moderate or severe SDB. In linear regression analysis, OAHI during REM was associated with the CV variables (daytime BP P = 0.032, ß = 0.748; nighttime BP P = 0.041, ß = 0.715), and the correlations remained significant after adjustments for BMI. However, we did not confirm a significant association with the metabolic variables. The prevalence of SDB was high, and its severity during REM was a predictor of the BP suggesting that RTx children with SDB might be at risk of developing CV complications, especially HTN similarly to adults.

Obstructive sleep apnea as a risk factor for incident end stage renal disease: a nationwide population-based cohort study from Korea

BACKGROUND

Obstructive sleep apnea (OSA) is known to be associated with metabolic dysregulation and incident cardiovascular diseases. However, its association with end-stage renal disease (ESRD) has not been clarified. This study aimed to evaluate longitudinally whether OSA is an independent risk factor for ESRD.

METHODS

This retrospective nationwide population-based cohort study included data on 67,359 patients with OSA and 336,795 age-, sex- and years of the enrollment-matched controls without OSA obtained from the Korean National Health Insurance Service database from 2009 to 2014. The study population was followed up from baseline to the date of ESRD diagnosis or until 2016. A Cox proportional-hazards model with multivariable adjustment was used to evaluate the association between OSA and incident ESRD.

RESULTS

A significantly higher incident ESRD risk (adjusted hazard ratio: 1.29, 95% confidence interval 1.02-1.62) was observed for patients older than 40 years with OSA than for matched controls, when adjusted for age, sex, income status, smoking, alcohol consumption, body mass index, diabetes, hypertension, dyslipidemia, estimated glomerular filtration rate, and proteinuria. The OSA group remained predictive of higher risk of ESRD incidence in subgroups of age ≥ 65 years, female sex, hypertension, dyslipidemia, proteinuria, and chronic kidney disease.

CONCLUSION

OSA was associated with a higher risk of incident ESRD. Understanding the association between OSA and ESRD might provide further insights to establish national health care policy.

Single-Dose Pharmacokinetics and Safety of Solriamfetol in Participants With Normal or Impaired Renal Function and With End-Stage Renal Disease Requiring Hemodialysis

Solriamfetol (JZP-110), a selective dopamine and norepinephrine reuptake inhibitor with wake-promoting effects, is renally excreted ∼90% unchanged within 48 hours. Effects of renal impairment and hemodialysis on the pharmacokinetics and safety of 75-mg single-dose solriamfetol were evaluated in adults with normal renal function (n = 6); mild (n = 6), moderate (n = 6), or severe (n = 6) renal impairment; and end-stage renal disease (ESRD) with and without hemodialysis (n = 7). Relative to normal renal function, geometric mean area under the plasma concentration-time curve from time zero to infinity increased 53%, 129%, and 339%, and mean half-life was 1.2-, 1.9-, and 3.9-fold higher with mild, moderate, and severe renal impairment, respectively. Renal excretion of unchanged solriamfetol over 48 hours was 85.8%, 80.0%, 66.4%, and 57.1% in normal, mild, moderate, and severe renal impairment groups, respectively; mean maximum concentration and time to maximum concentration did not vary substantially. Decreases in solriamfetol clearance were proportional to decreases in estimated glomerular filtration rate. Geometric mean area under the plasma concentration-time curve from time zero to time of last quantifiable concentration increased 357% and 518% vs normal in ESRD with and without hemodialysis, respectively, with half-life >100 hours in both groups. Over the 4-hour hemodialysis period, ∼21% of solriamfetol dose was removed. Adverse events included headache (n = 1) and nausea (n = 1). Six days after dosing, 1 participant had increased alanine and aspartate aminotransferase, leading to study discontinuation. While these adverse events were deemed study-drug related, they were mild and resolved. Results from this study combined with population pharmacokinetic modeling/simulation suggest that solriamfetol dosage adjustments are necessary in patients with moderate or severe but not with mild renal impairment. Due to significant exposure increase/prolonged half-life, dosing is not recommended in patients with ESRD.

Obstructive sleep apnea and chronic kidney disease

PURPOSE OF REVIEW

Obstructive sleep apnea (OSA) is highly prevalent in patients with chronic kidney disease (CKD). The relationship between OSA and CKD is likely to be bi-directional. On one hand, the presence of OSA leads to intermittent hypoxia, sympathetic nervous system activity, and hypertension, all of which may have deleterious effects on kidney function. On the other hand, in patients with end-stage renal disease (ESRD), intensification of renal replacement therapy has been shown to attenuate sleep apnea severity, suggesting that the renal disease itself contributes to the pathogenesis of OSA. The present review describes our current understanding of the bi-directional relationship between OSA and CKD.

RECENT FINDINGS

Studies suggest that the presence of OSA and nocturnal hypoxia may lead to worsening of kidney function. One potential mechanism is activation of the renin-angiotensin system by OSA, an effect which may be attenuated by CPAP therapy. In ESRD, fluid overload plays an important role in the pathogenesis of OSA and fluid removal by ultrafiltration leads to marked improvements in sleep apnea severity.

SUMMARY

OSA is associated with accelerated loss of kidney function. In patients with ESRD, fluid overload plays an important role in the pathogenesis of OSA.

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.

Interventions for improving sleep quality in people with chronic kidney disease

BACKGROUND

Sleep disorders are commonly experienced by people with chronic kidney disease (CKD). Several approaches for improving sleep quality are used in clinical practice including relaxation techniques, exercise, acupressure, and medication.

OBJECTIVES

To assess the effectiveness and associated adverse events of interventions designed to improve sleep quality among adults and children with CKD including people with end-stage kidney disease (ESKD) treated with dialysis or kidney transplantation.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 8 October 2018 with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) or quasi-randomised RCTs of any intervention in which investigators reported effects on sleep quality. Two authors independently screened titles and abstracts of identified records.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the risk of bias for included studies. The primary outcomes were sleep quality, sleep onset latency, sleep duration, sleep interruption, and sleep efficiency. Risks of bias were assessed using the Cochrane tool. Evidence certainty was assessed using the GRADE approach. We calculated treatment estimates as risk ratios (RR) for dichotomous outcomes or mean difference (MD) or standardised MD (SMD) for continuous outcomes to account for heterogeneity in measures of sleep quality.

MAIN RESULTS

Sixty-seven studies involving 3427 participants met the eligibility criteria. Thirty-six studies involving 2239 participants were included in meta-analyses. Follow-up for clinical outcomes ranged between 0.3 and 52.8 weeks (median 5 weeks). Interventions included relaxation techniques, exercise, acupressure, cognitive-behavioural therapy (CBT), educational interventions, benzodiazepine treatment, dopaminergic agonists, telephone support, melatonin, reflexology, light therapy, different forms of peritoneal dialysis, music, aromatherapy, and massage. Incomplete reporting of key methodological details resulted in uncertain risk of bias in many studies.In very low certainty evidence relaxation techniques had uncertain effects on sleep quality and duration, health-related quality of life (HRQoL), depression, anxiety, and fatigue. Studies were not designed to evaluate the effects of relaxation on sleep latency or hospitalisation. Exercise had uncertain effects on sleep quality (SMD -1.10, 95% CI -2.26 to 0.05; I2 = 90%; 5 studies, 165 participants; very low certainty evidence). Exercise probably decreased depression (MD -9.05, 95% CI -13.72 to -4.39; I2 = 0%; 2 studies, 46 participants; moderate certainty evidence) and fatigue (SMD -0.68, 95% CI -1.07 to -0.29; I2 = 0%; 2 studies, 107 participants; moderate certainty evidence). Compared with no acupressure, acupressure had uncertain effects on sleep quality (Pittsburgh Sleep Quality Index (PSQI) scale 0 - 21) (MD -1.27, 95% CI -2.13 to -0.40; I2 = 89%; 6 studies, 367 participants: very low certainty evidence). Acupressure probably slightly improved sleep latency (scale 0 - 3) (MD -0.59, 95% CI -0.92 to -0.27; I2 = 0%; 3 studies, 173 participants; moderate certainty evidence) and sleep time (scale 0 - 3) (MD -0.60, 95% CI -1.12 to -0.09; I2 = 68%; 3 studies, 173 participants; moderate certainty evidence), although effects on sleep disturbance were uncertain as the evidence certainty was very low (scale 0 - 3) (MD -0.49, 95% CI -1.16 to 0.19; I2 = 97%). In moderate certainty evidence, acupressure probably decrease fatigue (MD -1.07, 95% CI -1.67 to -0.48; I2 = 0%; 2 studies, 137 participants). Acupressure had uncertain effects on depression (MD -3.65, 95% CI -7.63 to 0.33; I2 = 27%; 2 studies, 137 participants; very low certainty evidence) while studies were not designed to evaluate the effect of acupressure on HRQoL, anxiety, or hospitalisation. It was uncertain whether acupressure compared with sham acupressure improved sleep quality (PSQI scale 0 to 21) because the certainty of the evidence was very low (MD -2.25, 95% CI -6.33 to 1.82; I2 = 96%; 2 studies, 129 participants), but total sleep time may have been improved (SMD -0.34, 95% CI -0.73 to 0.04; I2 = 0%; 2 studies, 107 participants; low certainty evidence). 2 =2 =There were no studies designed to directly examine and/or correlate efficacy of any interventions aimed at improving sleep that may have been attempted for the spectrum of sleep disordered breathing. No studies reported treatment effects for children. Adverse effects of therapies were very uncertain.

AUTHORS' CONCLUSIONS

The evidence base for improving sleep quality and related outcomes for adults and children with CKD is sparse. Relaxation techniques and exercise had uncertain effects on sleep outcomes. Acupressure may improve sleep latency and duration, although these findings are based on few studies. The effects of acupressure were not confirmed in studies in which sham acupressure was used as the control. Given the very low certainly evidence, future research will very likely change the evidence base. Based on the importance of symptom management to patients, caregivers and clinicians, future studies of sleep interventions among people with CKD should be a priority.

Effect of CPAP therapy on kidney function in patients with obstructive sleep apnoea and chronic kidney disease: a protocol for a randomised controlled clinical trial

INTRODUCTION

Obstructive sleep apnoea (OSA) is common in patients with chronic kidney disease (CKD) and may contribute to the progression of kidney disease either through direct effects of hypoxia on the kidney or indirectly through hypoxaemia-induced oxidative stress, endothelial dysfunction, inflammation, activation of the renin-angiotensin and sympathetic nervous systems, and hypertension. Treatment of OSA with continuous positive airway pressure (CPAP) improves many of these physiological abnormalities in patients with normal renal function, though to date there are no trials evaluating the effect of OSA treatment on kidney function in patients with CKD. The purpose of this study is to test the feasibility and efficacy of CPAP therapy in CKD patients with OSA.

METHODS AND ANALYSIS

The study is a randomised, controlled, non-blinded, parallel clinical trial in which patients with established CKD are screened for OSA. Patients with OSA are randomised to either conventional medical therapy (control group) or medical therapy and CPAP (CPAP group) and followed for 1 year. The primary outcome is the change in estimated glomerular filtration rate. Secondary outcomes are the change in the urinary albumin/creatinine ratio, the Epworth Sleepiness Scale , Pittsburgh Sleep Quality Index and Kidney Disease Quality of Life questionnaire.

ETHICS AND DISSEMINATION

Ethics approval has been obtained from the Conjoint Health Research Ethics Board (ID: REB15-0055). Results from this study will be disseminated through presentations at scientific conferences and publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT02420184; Pre-results.

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.

The pedunculopontine tegmentum controls renal sympathetic nerve activity and cardiorespiratory activities in nembutal-anesthetized rats

Elevated renal sympathetic nerve activity (RSNA) accompanies a variety of complex disorders, including obstructive sleep apnea, heart failure, and chronic kidney disease. Understanding pathophysiologic renal mechanisms is important for determining why hypertension is both a common sequelae and a predisposing factor of these disorders. The role of the brainstem in regulating RSNA remains incompletely understood. The pedunculopontine tegmentum (PPT) is known for regulating behaviors including alertness, locomotion, and rapid eye movement sleep. Activation of PPT neurons in anesthetized rats was previously found to increase splanchnic sympathetic nerve activity and blood pressure, in addition to altering breathing. The present study is the first investigation of the PPT and its potential role in regulating RSNA. Microinjections of DL-homocysteic acid (DLH) were used to probe the PPT in 100-μm increments in Nembutal-anesthetized rats to identify effective sites, defined as locations where changes in RSNA could be evoked. A total of 239 DLH microinjections were made in 18 rats, which identified 20 effective sites (each confirmed by the ability to evoke a repeatable sympathoexcitatory response). Peak increases in RSNA occurred within 10–20 seconds of PPT activation, with RSNA increasing by 104.5 ± 68.4% (mean ± standard deviation) from baseline. Mean arterial pressure remained significantly elevated for 30 seconds, increasing from 101.6 ± 18.6 mmHg to 135.9 ± 36.4 mmHg. DLH microinjections also increased respiratory rate and minute ventilation. The effective sites were found throughout the rostal-caudal extent of the PPT with most located in the dorsal regions of the nucleus. The majority of PPT locations tested with DLH microinjections did not alter RSNA (179 sites), suggesting that the neurons that confer renal sympathoexcitatory functions comprise a small component of the PPT. The study also underscores the importance of further investigation to determine whether sympathoexcitatory PPT neurons contribute to adverse renal and cardiovascular consequences of diseases such as obstructive sleep apnea and heart failure.

Factors associated with severity of sleep apnoea syndrome in patients with chronic kidney disease

Background In patients with chronic kidney disease (CKD), prevalence of sleep apnoea syndrome (SAS) is reported to be markedly high. However, the factors associated with severity of SAS in such patients rarely have been reported. Methods This was a cross-sectional study of 100 stable non-dialysis patients with CKD who attended a CKD educational programme from April 2014 to August 2015. Diagnosis of SAS and its severity were assessed using a type-3 portable monitor. Results Eighty-six men and 14 women with a mean age of 71.6 ± 9.7 years were included. Mean apnoea-hypopnoea index (AHI) was 26.0 ± 13.8. Severe SAS was seen in 39 patients. Significant differences in brain natriuretic peptide (BNP) level (213.6 ± 329.6 pg/mL vs 107.8 ± 141.3 pg/mL, P < 0.05) and cardiothoracic ratio (CTR, 52.4% ± 6.3% vs 49.6% ± 5.7%, P < 0.05) were seen between patients with and without severe SAS. After adjusting for various parameters, BNP level, CTR, and diameter of the inferior vena cava at the end of inhalation were found to correlate with AHI. Conclusions In patients with CKD, prevalence of severe SAS is extremely high. In these patients, fluid retention, rather than systolic or diastolic function, correlates with severity of SAS.

Sleep apnea syndrome, inflammation and oxidative stress in hemodialysis patients

INTRODUCTION

Sleep apnea syndrome (SAS) is an established cardiovascular risk factor in the general population related to inflammation and oxidative stress and is very common among hemodialysis patients. Cardiovascular disease and its complications is the main cause of death among hemodialysis patients. The aim of the present study was to investigate the role of SAS in the promotion of inflammation and oxidative stress and thus in the augmentation of cardiovascular risk in hemodialysis patients.

METHODS

Thirty-seven hemodialysis patients underwent an overnight full polysomnography study. The following morning blood samples were obtained and TNF-α (tumor necrosis factor-α), IL-6 (interleukin-6), MPO (myeloperoxidase), and oxLDL (oxidized low density lipoprotein) were measured.

FINDINGS

We investigated the correlation of patients' markers of inflammation and oxidative stress with their sleep parameters (total sleep time, AHI, apnea/hypopnea index; RDI, respiratory disturbance index; DI, desaturation index, mean and minimum SpO₂ and percentage of sleep time with SpO₂  < 90%). TNF-α correlated positively with BMI (r = 0.510, P < 0.0001) and total sleep time (r = 0.370, P = 0.027). IL-6 correlated positively with age (r = 0.363, P = 0.027), AHI (r = 0.385, P = 0.018), DI (r = 0.336, P = 0.042) and percentage of sleep time with SpO₂  < 90% (r = 0.415, P = 0.012) and negatively with mean SpO₂ (r = -0.364, P = 0.027). Myeloperoxidase correlated positively with AHI (r = 0.385, P = 0.018), DI (r = 0.380, P = 0.02) and percentage of sleep time with SpO₂  < 90% (r = 0.388, P = 0.019). Finally, oxLDL correlated positively with BMI (r = 0.443, P = 0.007), AHI (r = 0.395, P = 0.015), RDI (r = 0.328, P = 0.048) and total sleep time with SpO₂ <90% (r = 0.389, P = 0.019).

CONCLUSIONS

These results indicate that, in hemodialysis patients, the severity of SAS and nocturnal hypoxia correlated positively with markers of inflammation and oxidative stress.

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.

Kidney-lung connections in acute and chronic diseases: current perspectives

Lung and kidney functions are intimately related in both health and disease. The regulation of acid-base equilibrium, modification of partial pressure of carbon dioxide and bicarbonate concentration, and the control of blood pressure and fluid homeostasis all closely depend on renal and pulmonary activities. These interactions begin in fetal age and are often responsible for the genesis and progression of diseases. In gestational age, urine is a fundamental component of the amniotic fluid, acting on pulmonary maturation and growth. Moreover, in the first trimester of pregnancy, kidney is the main source of proline, contributing to collagen synthesis and lung parenchyma maturation. Pathologically speaking, the kidneys could become damaged by mediators of inflammation or immuno-mediated factors related to a primary lung pathology or, on the contrary, it could be the renal disease that determines a consecutive pulmonary damage. Furthermore, non immunological mechanisms are frequently involved in renal and pulmonary diseases, as observed in chronic pathologies such as sleep apnea syndrome, pulmonary hypertension, progressive renal disease and hemodialysis. Kidney damage has also been related to mechanical ventilation. The aim of this review is to describe pulmonary-renal interactions and their related pathologies, underscoring the need for a close collaboration between intensivists, pneumologists and nephrologists.

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.

Nocturnal hypoxemia severity and renin-angiotensin system activity in obstructive sleep apnea

RATIONALE

Obstructive sleep apnea (OSA) and nocturnal hypoxemia are associated with chronic kidney disease and up-regulation of the renin-angiotensin system (RAS), which is deleterious to renal function. The extent to which the magnitude of RAS activation is influenced by the severity of nocturnal hypoxemia and comorbid obesity has not been determined.

OBJECTIVES

To determine the association between the severity of nocturnal hypoxemia and RAS activity and whether this is independent of obesity in patients with OSA.

METHODS

Effective renal plasma flow (ERPF) response to angiotensin II (AngII) challenge, a marker of renal RAS activity, was measured by paraaminohippurate clearance technique in 31 OSA subjects (respiratory disturbance index, 51 ± 25 h(-1)), stratified according to nocturnal hypoxemia status (mean nocturnal SaO2, ≥90% [moderate hypoxemia] or <90% [severe hypoxemia]) and 13 obese control subjects.

MEASUREMENTS AND MAIN RESULTS

Compared with control subjects, OSA subjects demonstrated decreased renovascular sensitivity (ERPF, -153 ± 79 vs. -283 ± 31 ml/min; P = 0.004) (filtration fraction, 5.4 ± 3.8 vs. 7.1 ± 2.6%; P = 0.0025) in response to 60 minutes of AngII challenge (mean ± SD; all P values OSA vs. control). The fall in ERPF in response to AngII was less in patients with severe hypoxemia compared with those with moderate hypoxemia (P = 0.001) and obese control subjects after 30 minutes (P < 0.001) and 60 minutes (P < 0.001) of AngII challenge, reflecting more augmented renal RAS activity. Severity of hypoxemia was not associated with the blood pressure or the systemic circulating RAS component response to AngII.

CONCLUSIONS

The severity of nocturnal hypoxemia influences the magnitude of renal, but not the systemic, RAS activation independently of obesity in patients with OSA.

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.

Dynamic changes of early-stage aortic lipid deposition in chronic renal failure rats and effects of decorin gene therapy

The aim of the present study was to clarify the association between lipid metabolism and the atherosclerosis in early-stage chronic renal failure at the molecular level and to explore the efficacy of decorin on chronic renal failure. Sprague Dawley rats receiving 5/6 nephrectomy and Sham surgery were divided into control and experimental groups. Sprague Dawley rats receiving 5/6 nephrectomy were divided into control and experimental groups, and the experimental group was further subdivided into rats receiving treatment with fibroblasts (FBs) transfected either with empty vector and with a decorin (DCN) gene. The dynamic levels of triglyceride (TG), total cholesterol (T-Ch) and total phospholipid (T-PL) were detected on the 10th, 30th and 60th days. The body weight, blood lipid levels, renal function and renal tissue were observed after four weeks, and transforming growth factor-βl and protein expression was detected by immunohistochemistry. In total, 4 weeks after treatment, the DCN expression in the renal tissue of rats treated with DCN-transfected FBs was significantly increased compared to that in the control rats. The results showed that the levels of the three lipids in the aortic arches were slightly elevated on the 10th day compared with those in the control group, and the TG level was significantly increased on the 30th day. The levels of T-Ch, TG and T-PL in the aortic arches were significantly elevated on the 60th day. The TG and T-Ch levels in the plasma and aortic tissues of Sprague Dawley rats receiving 5/6 nephrectomy without any treatment and after receiving treatment with FBs transfected with empty vector were significantly increased compared with those in the control group. The increased T-Ch and decreased T-PL levels in the erythrocyte membrane increased the rigidity of the erythrocyte and decreased erythrocyte deformability. In conclusion, highly expressed DCN mitigated renal fibrosis and thus delayed renal failure as well as mitigating the abnormal lipid metabolism of the chronic renal failure.

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 apnea is not associated with worse outcomes in kidney transplant recipients

Obstructive sleep apnea(OSA) is one of the most common sleep disorders in kidney transplant recipients, however its long-term consequences have only rarely been investigated. Here, we hypothesized that the presence of OSA would be associated with higher risk of mortality and faster decline of graft function in kidney transplant recipients. In a prospective cohort study 100 prevalent kidney transplant recipients who underwent one-night polysomnography at baseline and were followed for a median 75 months. Generalized linear mixed-effects models and Cox regression models were used to assess the association between OSA and the rate of progression of chronic kidney disease(CKD) and mortality. The estimated slopes of estimated glomerular filtration rate(eGFR) in patients with and without OSA were compared using a two-stage model of eGFR change including only OSA as a variable. In this model patients with OSA (eGFR versus time was −0.93 ml/min/1.73 m²/yr(95%CI:−1.75 to−0.11) had a similar slope as compared to patients without OSA(eGFR versus time was −1.24 ml/min/1.73 m²/yr(95%CI: −1.67 to −0.81). In unadjusted Cox proportional regression analyses OSA was not associated with higher all-cause mortality risk (Hazard Ratio(HR) = 1.20; 95% Confidence Interval(CI): 0.50–2.85). No association was found between the presence of OSA and the rate of progression of CKD or all-cause mortality in prevalent kidney transplant recipients.

Evaluation of continuous positive airway pressure therapy on renin-angiotensin system activity in obstructive sleep apnea

RATIONALE

Obstructive sleep apnea (OSA) has been associated with kidney function loss, which may be related to changes in the renin-angiotensin system (RAS).

OBJECTIVES

We sought to determine the effect of continuous positive airway pressure (CPAP) of patients with OSA on renal hemodynamics at baseline and in response to angiotensin II (AngII), which reflects RAS activity.

METHODS

Twenty normotensive, nondiabetic, newly diagnosed OSA subjects (15 men, 5 women, 50 ± 2 yr, respiratory disturbance index [RDI] > 15 h(-1)) with nocturnal hypoxemia (SaO2 < 90% for >12% of the night) were studied in high-salt balance pre- and post-CPAP therapy (>4 h CPAP use/night for 1 mo). Glomerular filtration rate (GFR), renal plasma flow (RPF), and filtration fraction (FF) (a surrogate marker for intraglomerular pressure) were measured pre- and post-CPAP using inulin and para-aminohippurate clearance techniques at baseline and in response to graded AngII infusion (3 ng/kg/min × 30 min and 6 ng/kg/min × 30 min, respectively).

MEASUREMENTS AND MAIN RESULTS

CPAP corrected OSA and hypoxemia (RDI: 42 ± 4 vs. 4 ± 1 h(-1), P < 0.001; duration SaO2 < 90%: 36% ± 5% vs. 6 ± 2%, P < 0.001). CPAP reduced GFR (124 ± 8 ml/min vs. 110 ± 6 ml/min, P = 0.014), increased RPF (692 ± 36 ml/min vs. 749 ± 40 ml/min, P = 0.059), and reduced baseline FF (18.9 ± 1.6% vs. 15.3 ± 1.0%, P = 0.004). Post-CPAP demonstrated a blunted GFR response (-9 ± 3 ml/min vs. -2 ± 2 ml/min, P = 0.033) and augmented RPF response (-182 ± 22 ml/min vs. -219 ± 25 ml/min, P = 0.024) to AngII. FF response was maintained (P = 0.4). CPAP reduced baseline mean arterial pressure (94 ± 2 vs. 89 ± 2 mm Hg, P = 0.002), plasma aldosterone (149 ± 18 vs. 109 ± 10 pmol/L, P = 0.003), and urinary protein excretion (61 [39-341] mg/day vs. 56 [22-204] mg/d, P = 0.003).

CONCLUSIONS

CPAP therapy was associated with improved renal hemodynamics and down-regulation of renal RAS activity, suggesting a potential therapeutic benefit for kidney function.

Effect of continuous positive airway pressure on serum cystatin C among obstructive sleep apnea syndrome patients

PURPOSE

The purpose of the present study was to evaluate the influence of continuous positive airway pressure (CPAP) on serum cystatin C, a novel biomarker of early renal impairment, among obstructive sleep apnea (OSA) patients.

MATERIALS AND METHODS

Newly diagnosed severe OSA patients who treated with CPAP for 3 months were enrolled from two sleep laboratories. Serum biomarkers of renal impairment, cystatin C, creatinine and estimated glomerular filtration rate (eGFR), were detected before and after CPAP treatment.

RESULTS

A total of 39 severe OSA patients were enrolled, 29 (74.4 %) were male, and mean age was 51.2 ± 12.2 years. After CPAP treatment, there were no changes of creatinine and eGFR (77.80 ± 20.00 vs. 75.3 ± 16.60 and 98.69 ± 31.74 vs. 100.20 ± 28.30, all p > 0.05), but cystatin C declined significantly (0.87 ± 0.18 vs. 0.77 ± 0.21, p = 0.000).

CONCLUSION

CPAP can decrease cystatin C levels among severe OSA patients and may prevent the latent renal impairment.

Restless legs syndrome in hemodialysis patients: an epidemiologic survey in Greece

BACKGROUND

Restless legs syndrome (RLS) is a sensorimotor disorder characterized by an uncontrolled need to move extremities accompanied by unpleasant sensations, which frequently leads to sleep disturbances. In hemodialysis (HD) patients, the previously reported RLS prevalence varied enormously, between 6% and 60%. In our study, we investigated the RLS prevalence in HD patients for the first time in Greece.

METHODS

A continuous sample of HD patients was studied between January and September of 2010 in six dialysis units in Greece. RLS diagnosis was based on the essential clinical criteria of the International RLS Study Group (IRLSSG). The standardized incidence ratio (SIR) for RLS in HD patients was calculated in comparison to data from a recent survey of the general population in Greece.

RESULTS

In our study of 579 HD patients in Greece (236 women; mean age, 65±13years), the prevalence of RLS was elevated in comparison to the general population (26.6% vs 3.9%), with an SIR of 5.4 (95% confidence interval [CI], 4.6-6.3). In the fully adjusted model, the risk for RLS in HD patients was reduced in older age (odds ratio [OR], 0.98 [95% CI, 0.96-0.99]) and increased in women (OR, 1.60 [95% CI, 1.05-2.43]) in cases with elevated levels of β2 microglobulin (OR, 1.15 [95% CI, 1.01-1.32]) and intact parathormone (iPTH) (OR, 1.30 [95% CI, 1.08-1.56]).

CONCLUSION

A high RLS prevalence was recorded in a large HD population in Greece, clearly suggesting the need for enhanced awareness of RLS in nephrology. The RLS risk was increased in women and in younger HD patients as well as in those with elevated β2 microglobulin and iPTH levels.

Association of nocturnal hypoxemia with progression of CKD

BACKGROUND AND OBJECTIVES

Nocturnal hypoxemia is highly prevalent among patients with CKD. Nocturnal hypoxemia contributes to systemic inflammation, oxidative stress, endothelial cell dysfunction, and activation of the renin-angiotensin system, which are common pathologic mechanisms of CKD progression. This study investigated whether nocturnal hypoxemia is independently associated with CKD progression.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This two-center retrospective cohort study included 161 patients with stages 3-4 CKD enrolled from January of 2009 to July of 2011 with a body mass index less than 25.0 kg/m(2). The 4% oxygen desaturation index, the number of events per hour in which oxygen saturation decreases by >4% during sleep, was measured, and the declining rate of the estimated GFR was followed over 1 year. The severity of nocturnal hypoxemia was categorized as none (oxygen desaturation index<5.0), mild (5.0≤oxygen desaturation index<15.0), or moderate to severe (15.0≤oxygen desaturation index).

RESULTS

The mean estimated GFR of the total cohort at baseline was 31 ml/min per 1.73 m(2). Eighty patients (49.7%) were diagnosed with nocturnal hypoxemia; 64 patients were diagnosed with mild nocturnal hypoxemia, and 16 patients were diagnosed with moderate-to-severe nocturnal hypoxemia. The estimated GFR declined three- to fourfold faster in patients with moderate-to-severe nocturnal hypoxemia than patients with no or mild nocturnal hypoxemia (the mean values [95% confidence intervals] were -2.14 [-1.06 to -3.21], -3.02 [-1.31 to -4.74], and -8.59 [-2.00 to -15.2] ml/min per 1.73 m(2) per year in the no, mild, and moderate-to-severe nocturnal hypoxemia groups, respectively; P=0.003). Nocturnal hypoxemia remained a significant predictor of decline in estimated GFR after adjustment for various baseline clinical factors.

CONCLUSIONS

In nonobese patients with CKD, nocturnal hypoxemia is an independent risk factor of a rapid decline in kidney function.

Restless legs syndrome and quality of sleep in patients with glomerulopathy

Background

Despite a confirmed association between restless legs syndrome (RLS) and end-stage renal disease (ESRD), there is no study on patients presenting with nephrotic syndrome (NS). To investigate the frequency of RLS and poor quality sleep in NS-patients secondary to primary glomerulopathy with nearly normal glomerular filtration rate (GFR) and its associated factors.

Methods

Patients with NS, defined as 24 h-urine protein greater than 3.5 g/1.73 m² and hypoalbuminemia, (n = 99, 53 women) and a mean age of 36±11 years were studied. Age and sex-matched controls were used to compare RLS and poor sleep quality prevalence. Standardized RLS questionnaire formulated by the International Restless Legs Syndrome and Pittsburgh Sleep Quality Index (PSQI) were used.

Results

RLS was more frequent in NS-patients than in controls (22.8 vs. 4.0%, p = 0.01). Mean time since diagnosis (52.2±34.1 vs. 28.6±22.5 months, p < 0.01) and 24 h-proteinuria (3.7±1.3 vs. 2.6±0.6 g/1.73 m², p = 0.001) were greater in NS-patients with RLS those not presenting RLS. Association between RLS with 24 h-proteinuria [OR = 2.31; p = 0.007; 95% CI 1.87-2.89] and time since diagnosis [OR = 1.10; p = 0.003; CI = 1.02-1.39] were identified even after controlling for age, GFR and diabetes. Sleep quality was poor in NS-patients than in controls (mean PSQI score 7.35±3.7 vs. 5.2±3.0, p = 0.003). In NS-patients, only RLS was associated with poor sleep quality (OR = 1.20; p = 0.004).

Conclusion

Poor quality sleep and RLS are frequent in NS-patients without ESRD. Pathophysiology of this association must be further investigated.

Diagnostic value of screening instruments for identifying obstructive sleep apnea in kidney failure

BACKGROUND

Patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD) have a high prevalence of obstructive sleep apnea (OSA) that can have significant clinical implications. An accurate clinical screening tool for OSA that identifies patients for further diagnostic testing would assist in the identification of this comorbidity. The Berlin Questionnaire (BQ), Adjusted Neck Circumference (ANC), and STOP-BANG questionnaire are 3 such instruments that have been validated in patients with normal kidney function.

OBJECTIVE

The objective of this study was to determine the validity of these screening instruments in patients with CKD and ESRD, using overnight cardiopulmonary monitoring to diagnose OSA.

METHODS

One hundred seventy-two patients were recruited from nephrology clinics and hemodialysis units (CKD: n = 109; ESRD: n = 63). All patients completed the BQ, ANC, STOP-BANG, and overnight cardiopulmonary monitoring to diagnose OSA (respiratory disturbance index [RDI] ≥ 15). Sensitivity, specificity, positive and negative predictive values, and accuracy were calculated for the BQ, ANC, and STOP-BANG.

RESULTS

Obstructive sleep apnea was present in 41 CKD patients (38%) and 32 ESRD patients (51%). All screening instruments had satisfactory sensitivity (56% to 94%) but poor specificity (29% to 77%) and low accuracy (51% to 69%) in both CKD and ESRD patients with RDI ≥ 15. Using an RDI ≥ 30 yielded similar results.

CONCLUSIONS

Current screening questionnaires do not accurately identify patients at high risk for OSA or rule out the presence of OSA in patients with CKD and ESRD. Consequently, objective monitoring during sleep is required to reliably identify sleep apnea in these patient populations.