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.

The Burden of Comorbidities in Obstructive Sleep Apnea and the Pathophysiologic Mechanisms and Effects of CPAP

Micro-arousals and the repeated desaturation of oxyhemoglobin, which are typical in obstructive sleep apnea syndrome (OSAS), have adverse effects on the health of patients, leading to a wide range of complications such as cardiovascular (arterial hypertension, pulmonary hypertension, chronic heart failure, arrhythmias, myocardial infarction), cerebrovascular (strokes), metabolic (insulin resistance, obesity, diabetes mellitus, metabolic syndrome), gastrointestinal (non-alcoholic liver disease), urinary (chronic renal failure), and neuropsychiatric complications as well as a wide range of malignancies. These, in turn, have multilateral effects on familial, occupational, and social life, as well as increasing the risks of road traffic accidents and accidents at the workplace. Awareness, timely screening, and the prevention of complications play important roles in diagnosing and treating comorbid conditions. This review focuses on comorbidities in OSAS and the effect of Continuous Positive Airway Pressure (CPAP) therapy on their prognoses.

Impact of the 3% Oxygen Desaturation Index via Overnight Pulse Oximetry on Cardiovascular Events and Death in Patients Undergoing Hemodialysis: A Retrospective Cohort Study

It is unclear whether the severity of sleep-disordered breathing (SDB) affects the risk of cardiovascular events and mortality in patients undergoing hemodialysis (HD). We determined the severity of SDB with the 3% oxygen desaturation index (ODI) via overnight pulse oximetry. This study was a retrospective cohort, observational study of 134 patients on maintenance HD at a single center. They were divided into four groups according to SDB severity (normal, mild, moderate, and severe), and were followed. The baseline characteristics of all patients were as follows: the median age was 67 (interquartile range, 59-75) years, 64.2% were men, 37.3% were diabetic, and the median duration of HD was 69 (29-132) months. During follow-up, major adverse cardiovascular events (MACEs) occurred in 71 patients and deaths in 60 (including 32 cardiovascular deaths). Severe SDB was an independent risk factor for MACEs (hazard ratio [HR] = 4.66, 95% confidence interval [CI] = 1.87-11.61, p = 0.001) and all-cause death (HR = 5.74, 95% CI = 1.92-16.70, p = 0.001). Severe SDB had a statistically significant impact on the risk of MACEs and mortality in patients undergoing HD. The severity of the 3% ODI via overnight pulse oximetry may be a useful marker as a risk factor for cardiovascular outcomes and mortality in these patients.

The effect of obstructive sleep apnea on the increased risk of cardiovascular disease: a systematic review and meta-analysis

BACKGROUND

Obstructive sleep apnea (OSA) is a disorder characterized by intermittent airway obstruction during sleep. The association between OSA and the incidence of cardiovascular disease (CVD) has been investigated in many studies; however, the results are not entirely consistent between studies. The aim of this study was to investigate the relationship between OSA and the risk of CVD through a meta-analysis of cohort studies.

METHODS

A systematic review and meta-analysis of literature was conducted using the PubMed, WoS, Embase, ScienceDirect, Scopus, and Web of Science databases up to the year 2020. In order to analyze the eligible studies, the stochastic effects model was used and the heterogeneity of the studies with the I² index was investigated. Data analysis was performed with Comprehensive Meta-Analysis software (Version 2).

RESULTS

A total of 24 studies were included in the meta-analysis according to the inclusion criteria. Twelve studies reported CVD results, 11 studies reported stroke results, 9 studies reported mortality results, and 8 studies reported CVD results. The odds ratio of CVD in patients with OSA 1.71 (1.17-2.27: 95% confidence interval) stroke in patients with OSA, 1.86 (1.28-2.69: 95% confidence interval), mortality in patients with OSA, 1.77 (1.37-2.29: 95% confidence interval) and CHD in patients with OSA, and 1.48 (1.06-2.28: 95% confidence interval) was obtained.

CONCLUSION

OSA is considered a cardiovascular risk factor. There is a relationship between the severity of OSA and the risk of cardiovascular disease. OSA increases the risk of heart attack, CHD, and death from cardiovascular disease.

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.

REM sleep latency as an independent risk for cardiovascular events in hemodialysis patients

Background

Clinical significance of objectively measured poor sleep quality (SQ) as a risk for cardiovascular disease (CVD) events is not well known in hemodialysis (HD) patients, independently of sleep‐related breathing disorders (SRBDs) and sleep‐related metabolic abnormality.

Methods

The present study investigated baseline levels of objective sleep architecture together with obstructive sleep apnea (OSA) and central sleep apnea (CSA) using polysomnography in 88 HD study participants (M/F, 56/32; age 68.4 ± 9.3). Then, HD study participants were monitored for the occurrence of new‐onset CVD events with a median (range) follow‐up period of 33 (1–64) months.

Results

Among various measures of SQ, log (REM sleep latency [REM‐SL]) (interval between sleep‐onset and the first REM period) alone correlated in negative manners with triglycerides and non‐HDL‐C in all study participants and with fasting plasma glucose and HbA1c in study participants with type‐2 diabetes mellitus. In the Kaplan–Meier analysis, HD study participants with shorter REM‐SL had a significantly higher rate of new‐onset CVD events than those with longer REM‐SL. Stepwise logistic regression analysis and multivariate Cox proportional hazard regression analysis identified shorter REM‐SL as an independent risk factor for the development of a new‐onset CVD events, independent of mean oxygen saturation, log (AHI+1), log (central AHI+1), diabetes mellitus, CVD history, systolic blood pressure, statins use, and non‐HDL‐C.

Conclusions

The present study demonstrated that reduction of REM‐SL is independently associated with a higher rate of new‐onset of CVD events, independent of SRBDs (OSA and CSA) and diabetes mellitus, non‐HDL‐C in HD study participants, suggesting impaired SQ as a potential CVD risk factor, and thus a definite treatment target to protect against CVD specifically in HD study participants. REM‐SL might be a new risk factor of CVD events in HD patients with SRBDs.

Pittsburgh Sleep Quality Index score predicts all-cause mortality in Chinese dialysis patients

BACKGROUND

The relationship between Pittsburgh Sleep Quality Index (PSQI) score and survival of dialysis patients has not been well studied. The aim of this study was to explore the association between PSQI score and all-cause mortality in dialysis patients.

METHODS

Fifty-one hemodialysis and 58 peritoneal dialysis patients were enrolled in this study. PSQI score > 5 and ≤ 5 indicated "poor sleepers" and "good sleepers", respectively. The primary outcome was all-cause mortality. Kaplan-Meier survival curve and Cox proportional hazards regression analysis were performed.

RESULTS

The median PSQI score was 7.0 (4.0-10.0). Sixty-seven (61.5%) patients had poor sleep quality (SQ). Compared with good sleepers, poor sleepers had significantly lower levels of hemoglobin [74.0 (61.0, 85.0) vs. 78.0 (68.0, 97.0), P = 0.03] and serum bicarbonate (18.0 ± 4.5 vs. 20.0 ± 3.7, P = 0.022). The follow-up time was 69.1 ± 29.9 months. By multivariate Cox proportional hazards analysis, PSQI total score was the independent risk factor of all-cause mortality [hazard ratio (HR) 1.20, 95% confidence interval (CI) 1.05-1.36, P = 0.007]. Restricted cubic spline (RCS) analysis showed that 7 was the cutoff value at which the effect of PSQI score on mortality changed. Patients with a PSQI score > 7 had a 2.96-fold increased risk of all-cause mortality (HR 2.96, 95% CI 1.15-7.61, P = 0.025).

CONCLUSIONS

PSQI score can be used as a predictor of all-cause mortality in dialysis patients, and those with PSQI > 7 were associated with increased odds of mortality.

Obstructive sleep apnea is associated with impaired renal function in patients with diabetic kidney disease

Obstructive sleep apnea (OSA) is a recognized risk factor for the development of diabetic kidney disease (DKD). Our objectives were to compare the urinary albumin-creatinine ratio (UACR) and estimated glomerular filtration rate (eGFR) of patients with DKD according to OSA severity, and to evaluate the contribution of sleep parameters to their renal function. In a multicenter, observational, cross-sectional study, 214 patients with DKD were recruited. After a sleep study, UACR and eGFR were measured, as well as serum creatinine, fasting glucose, glycated hemoglobin, insulin resistance, lipid profile and C-reactive protein. UACR was higher in severe OSA patients (920 ± 1053 mg/g) than in moderate (195 ± 232 mg/g, p < 0.001) or mild OSA/non-OSA subjects (119 ± 186 mg/g, p < 0.001). At the same time, eGFR showed an OSA severity-dependent reduction (48 ± 23 vs. 59 ± 21 vs. 73 ± 19 ml/min per 1.73 m², respectively; p < 0.001). Apnea-hypopnea index (AHI and desaturation index (ODI) were identified as independent predictors for UACR and eGFR, respectively. Therefore, in patients with DKD under optimized treatment, severe OSA is associated with a higher UACR and a lower eGFR, reflecting an additional contribution to the impairment of their renal function, although no causality can be inferred.

Bidirectional association between chronic kidney disease and sleep apnea: a systematic review and meta-analysis

BACKGROUND

Previous data have suggested a link between chronic kidney disease (CKD) and sleep apnea (SA). However, the prevalence and risk association of both disease entities are not uniformly described.

METHODS

Ovid MEDLINE, EMBASE, and the Cochrane Library were searched for eligible publications that included patients aged ≥ 18 years diagnosed with CKD or SA. Included studies were divided into two cohorts: (1) a cohort of CKD or end-stage kidney disease (ESKD) patients reporting the prevalence of SA or odds ratio (OR) for SA (CKD cohort) and (2) a cohort of SA patients reporting the prevalence of CKD/ESKD or OR for CKD/ESKD (SA cohort).

RESULTS

CKD cohort: Of 16 studies (n = 340,587), the pooled estimated prevalence of SA among CKD/ESKD patients was 47.5% (95% CI 28.8-66.9). The pooled adjusted OR for SA among CKD/ESKD patients was 1.961 (95% CI 1.702-2.260). Male sex, history of diabetes, and lower BMI were associated with increased prevalence of SA. SA cohort: Of 12 studies (n = 3,103,074), the pooled prevalence of CKD/ESKD among patients with SA was 8.2% (95% CI 4.7-13.7), whereas the pooled adjusted OR for CKD/ESKD among patients with SA was 2.088 (95% CI 1.777-2.452). Increasing age, higher BMI, male sex, white race, and history of diabetes were associated with higher prevalence of CKD/ESKD.

CONCLUSION

There was a bidirectional association between CKD/ESKD and SA. Interventions aiming to prevent the progression of either CKD or SA are important.

Chronic kidney disease and concomitant sleep apnea are associated with increased overall mortality: a meta-analysis

PURPOSE

Sleep apnea (SA) is common in advanced chronic kidney disease (CKD) patients. However, the association between CKD with concomitant SA and overall mortality remains inconclusive.

METHODS

Ovid MEDLINE, EMBASE, and the Cochrane Library were searched for eligible publications, including non-transplant CKD patients aged > 18 years with co-existing SA. CKD is defined by estimated glomerular filtration rate of < 60 mL/min/1.73 m².

RESULTS

Seven observational studies (n = 186,686) were included in the meta-analyses. 94.2% had end-stage kidney disease (ESKD) requiring hemodialysis (HD), 5.0% had ESKD requiring peritoneal dialysis (PD), and 0.8% had non-dialysis CKD. The mean age was 76.8 ± 2.2 years. Most patients were male (53.4%) and white (76.8%). Up to 39.3% had diabetes. The mean body mass index was 26.0 ± 0.6 kg/m². Among patients with advanced CKD and SA, the pooled estimated odds ratios (OR) for overall mortality and cardiovascular events were 2.092 (95% CI, 1.594-2.744) and 1.020 (95% CI, 0.929-1.119), respectively, compared to patients with CKD alone. The OR was 2.145 (95% CI, 1.563-2.944) when studies with polysomnography-diagnosed SA were examined independently. No potential publication bias was detected. There were no significant differences in odds ratios for overall mortality, based on subgroup analyses.

CONCLUSION

Co-existence between advanced CKD and SA is associated with increased overall mortality, but not cardiovascular (CV) events when compared with CKD alone. The analysis of CV events requires additional studies to confirm our findings. Moreover, clinical interventions aiming to prevent the progression of SA and CKD are encouraged.

Association of Sleep Apnea with Mortality in Patients with Advanced Kidney Disease

BACKGROUND AND OBJECTIVES

In the general population, sleep disorders are associated with mortality. However, such evidence in patients with CKD and ESKD is limited and shows conflicting results. Our aim was to examine the association of sleep apnea with mortality among patients with CKD and ESKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this prospective cohort study, 180 patients (88 with CKD stage 4 or 5, 92 with ESKD) underwent in-home polysomnography, and sleep apnea measures such as apnea hypopnea index (AHI) and nocturnal hypoxemia were obtained. Mortality data were obtained from the National Death Index. Cox proportional hazard models were used for survival analysis.

RESULTS

Among the 180 patients (mean age 54 years, 37% women, 39% with diabetes, 49% CKD with mean eGFR 18±7 ml/min per 1.73 m²), 71% had sleep apnea (AHI>5) and 23% had severe sleep apnea (AHI>30). Median AHI was 13 (range, 4-29) and was not significantly different in patients with advanced CKD or ESKD. Over a median follow-up of 9 years, there were 84 (47%) deaths. AHI was not significantly associated with mortality after adjusting for age, sex, race, diabetes, body mass index, CKD/ESKD status, and kidney transplant status (AHI>30: hazard ratio [HR], 1.5; 95% confidence interval [95% CI], 0.6 to 4.0; AHI >15 to 30: HR, 2.3; 95% CI, 0.9 to 5.9; AHI >5 to 15: HR, 2.1; 95% CI, 0.8 to 5.4, compared with AHI≤5). Higher proportion of sleep time with oxygen saturation <90% and lower mean oxygen saturation were significantly associated with higher mortality in adjusted analysis (HR, 1.4; 95% CI, 1.1 to 1.7; P=0.007 for every 15% higher proportion, and HR, 1.6; 95% CI, 1.2 to 2.1; P=0.003 for every 2% lower saturation, respectively). Sleep duration, sleep efficiency, or periodic limb movement index were not associated with mortality.

CONCLUSIONS

Hypoxemia-based measures of sleep apnea are significantly associated with increased risk of death among advanced CKD and ESKD.

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.

Relación entre calidad del sueño, ansiedad y depresión en pacientes con enfermedad renal crónica en hemodiálisis

Introducción. Los trastornos de sueño tienen una alta prevalencia en los pacientes con Enfermedad Renal Crónica en Hemodiálisis. Un descanso insuficiente o de mala calidad influye negativamente en la actividad cotidiana siendo causa o consecuencia de estados depresivos o ansiosos. Objetivo. Evaluar la calidad del sueño en pacientes en hemodiálisis y su relación con los niveles de depresión y ansiedad. Material y Método. Estudio observacional descriptivo con inclusión de 28 pacientes en hemodiálisis durante febrero de 2017. Se recogieron datos sociodemográficos, se administró el test Pittsburg de Calidad del Sueño, y se valoró el estado cognitivo con el examen Minimental y la depresión y ansiedad con la Hospital Anxiety and Depression Scale (HADS). Resultados. El 82,14% (n=23) presentó insomnio según el test de Pittsburg. Los resultados obtenidos con el HADS fueron positivos para ansiedad en un 21% (n=6) y positivos para depresión en un 35% (n=10). Los resultados en el test Pittsburg se correlacionaron positivamente con los niveles de ansiedad (p=0,004) y depresión (p=0,049). El grado de depresión se correlacionó negativamente con ausencia de deterioro cognitivo (p=0,010). Conclusiones. La calidad del sueño en los pacientes examinados es mala y se pueden relacionar con los resultados de depresión y ansiedad encontrados. Según estos resultados, incluiremos información sobre hábitos de sueño saludables en el proceso de educación a pacientes en hemodiálisis, así como pretendemos mejorar la detección y tratamiento especializado de la ansiedad y depresión.

Alteraciones del sueño más frecuentes en las personas en diálisis

Introducción: La persona con enfermedad renal crónica en terapia dialítica presenta alteraciones en diferentes dimensiones de su vida, entre ellos el sueño, considerado una de las necesidades biológicas más importantes del organismo. Objetivo: Conocer las principales alteraciones del sueño en pacientes con ERC en tratamiento dialítico, los factores que influyen en su aparición y cuidados de enfermería. Metodología: Revisión narrativa de la literatura. Los criterios de inclusión fueron estudios primarios y revisiones sistemáticas, tanto cualitativos como cuantitativos, sobre alteraciones del sueño en pacientes adultos con ERC en terapia dialítica. Se consultaron las bases de datos Medline, Scielo y Epistemonikos. Resultados: La prevalencia de trastornos del sueño es alta en personas con enfermedad renal crónica que se someten a diálisis, las principales son síndrome de piernas inquietas y síndrome de apnea obstructiva del sueño. En el primero, el principal factor causal es el déficit de hierro y disfunción de dopamina, mientras que en el segundo son la sobrecarga de volumen y estrechez de vías respiratorias. El manejo responde a medidas farmacológicas como administración de hierro, agentes dopaminérgicos y uso de CPAP, además de medidas no farmacológicas que son transversales a ambos, como higiene del sueño. Conclusión: Las alteraciones del sueño en los pacientes en diálisis claramente repercuten en su calidad de vida, por lo que es un aspecto en que los profesionales de salud debiesen adquirir conocimientos y otorgar cuidados de enfermería específicos para prevenir, atenuar síntomas y evitar complicaciones.

Obstructive Sleep Apnea Increases Sudden Cardiac Death in Incident Hemodialysis Patients

BACKGROUND

Mortality in end-stage renal disease (ESRD) occurs predominantly from cardiovascular disease (CVD) and sudden cardiac death (SCD). Obstructive sleep apnea (OSA) is characterized by periodic airflow limitation associated with sleep arousal and oxygen desaturation and is prevalent in patients with ESRD. Whether OSA increases the risk for SCD, cardiovascular and all-cause mortality among hemodialysis patients remains unknown.

METHODS

In a prospective cohort of 558 incident hemodialysis patients, we examined the association of OSA with all-cause mortality, cardiovascular mortality, and SCD using Cox proportional hazards models controlling for traditional CVD risk factors.

RESULTS

Sixty-six incident hemodialysis patients (12%) had OSA. Mean age (56 years) and percentage of males (56%) were identical in OSA and no-OSA groups. Fewer African Americans had OSA than non-African Americans (9 vs. 18%, respectively). Participants with OSA had higher body-mass index, Charlson comorbidity score, and left ventricular mass index and greater prevalence of diabetes and coronary artery disease. During 1,080 person-years of follow-up, 104 deaths occurred, 29% of which were cardiovascular. OSA was associated with a higher risk of all-cause mortality (HR 1.90 [95% CI 1.04-3.46]) and cardiovascular mortality (HR 3.62 [95% CI 1.36-9.66]) after adjusting for demographics and body-mass index. OSA was associated with a higher risk of SCD after adjusting for demographics (HR 3.28 [95% CI 1.12-9.57]) and multiple cardiovascular risk factors.

CONCLUSIONS

Incident hemodialysis patients with OSA are at increased risk of all-cause and cardiovascular mortality and SCD. Future studies should assess the impact of screening for OSA and OSA-targeted interventions on mortality in ESRD.

Fluid Redistribution in Sleep Apnea: Therapeutic Implications in Edematous States

Sleep apnea (SA), a condition associated with increased cardiovascular risk, has been traditionally associated with obesity and aging. However, in patients with fluid-retaining states, such as congestive heart failure and end-stage renal disease, both prevalence and severity of SA are increased. Recently, fluid shift has been recognized to play an important role in the pathophysiology of SA, since the fluid retained in the legs during the day shifts rostrally while recumbent, leading to edema of upper airways. Such simple physics, observed even in healthy individuals, has great impact in patients with fluid overload. Correction of the excess fluid volume has risen as a potential target therapy to improve SA, by attenuation of nocturnal fluid shift. Such strategy has gained special attention, since the standard treatment for SA, the positive airway pressure, has low compliance rates among its users and has failed to reduce cardiovascular outcomes. This review focuses on the pathophysiology of edema and fluid shift, and summarizes the most relevant findings of studies that investigated the impact of treating volume overload on SA. We aim to expand horizons in the treatment of SA by calling attention to a potentially reversible condition, which is commonly underestimated in clinical practice.

Association between circulating fibroblast growth factor 21 and mortality in end-stage renal disease

Fibroblast growth factor 21 (FGF21) is an endocrine factor that regulates glucose and lipid metabolism. Circulating FGF21 predicts cardiovascular events and mortality in type 2 diabetes mellitus, including early-stage chronic kidney disease, but its impact on clinical outcomes in end-stage renal disease (ESRD) patients remains unclear. This study enrolled 90 ESRD patients receiving chronic hemodialysis who were categorized into low- and high-FGF21 groups by the median value. We investigated the association between circulating FGF21 levels and the cardiovascular event and mortality during a median follow-up period of 64 months. A Kaplan-Meier analysis showed that the mortality rate was significantly higher in the high-FGF21 group than in the low-FGF21 group (28.3% vs. 9.1%, log-rank, P = 0.034), while the rate of cardiovascular events did not significantly differ between the two groups (30.4% vs. 22.7%, log-rank, P = 0.312). In multivariable Cox models adjusted a high FGF21 level was an independent predictor of all-cause mortality (hazard ratio: 3.98; 95% confidence interval: 1.39–14.27, P = 0.009). Higher circulating FGF21 levels were associated with a high mortality rate, but not cardiovascular events in patient with ESRD, suggesting that circulating FGF21 levels serve as a predictive marker for mortality in these subjects.

Impact of Compression Stockings vs. Continuous Positive Airway Pressure on Overnight Fluid Shift and Obstructive Sleep Apnea among Patients on Hemodialysis

INTRODUCTION

Obstructive sleep apnea (OSA) is common in edematous states, notably in hemodialysis patients. In this population, overnight fluid shift can play an important role on the pathogenesis of OSA. The effect of compression stockings (CS) and continuous positive airway pressure (CPAP) on fluid shift is barely known. We compared the effects of CS and CPAP on fluid dynamics in a sample of patients with OSA in hemodialysis, through a randomized crossover study.

METHODS

Each participant performed polysomnography (PSG) at baseline, during CPAP titration, and after 1 week of wearing CS. Neck circumference (NC) and segmental bioelectrical impedance were done before and after PSG.

RESULTS

Fourteen patients were studied (53 ± 9 years; 57% men; body mass index 29.7 ± 6.8 kg/m²). Apnea-hypopnea index (AHI) decreased from 20.8 (14.2; 39.6) at baseline to 7.9 (2.8; 25.4) during CPAP titration and to 16.7 (3.5; 28.9) events/h after wearing CS (CPAP vs. baseline, p = 0.004; CS vs. baseline, p = 0.017; and CPAP vs. CS, p = 0.017). Nocturnal intracellular trunk water was higher after wearing CS in comparison to baseline and CPAP (p = 0.03). CS reduced the fluid accumulated in lower limbs during the day, although not significantly. Overnight fluid shift at baseline, CPAP, and CS was -183 ± 72, -343 ± 220, and -290 ± 213 ml, respectively (p = 0.006). Overnight NC increased at baseline (0.7 ± 0.4 cm), decreased after CPAP (-1.0 ± 0.4 cm), and while wearing CS (-0.4 ± 0.8 cm) (CPAP vs. baseline, p < 0.0001; CS vs. baseline, p = 0.001; CPAP vs. CS, p = 0.01).

CONCLUSION

CS reduced AHI by avoiding fluid retention in the legs, favoring accumulation of water in the intracellular component of the trunk, thus avoiding fluid shift to reach the neck. CPAP improved OSA by exerting local pressure on upper airway, with no impact on fluid redistribution. CPAP performed significantly better than CS for both reduction of AHI and overnight reduction of NC. Complementary studies are needed to elucidate the mechanisms by which CPAP and CS reduce NC.

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.

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.

Diabetic kidney disease and obstructive sleep apnea: a new frontier?

PURPOSE OF REVIEW

Obstructive sleep apnea (OSA) has been shown to be an independent risk factor for the development and progression of diabetes mellitus. Interestingly, there is also a strong correlation between OSA and the development and progression of chronic kidney disease (CKD). As diabetes mellitus is the most common cause of CKD, in this review we summarize the current literature regarding this interconnecting relationship between OSA, CKD, and diabetes mellitus. The literature increasingly supports a bidirectional relationship between CKD and OSA among diabetes mellitus patients leading to an increased rate of progression of diabetic nephropathy.

RECENT FINDINGS

There is growing evidence that among patients with diabetes mellitus, OSA may be a strong risk factor for the development of diabetic nephropathy. The treatment of OSA in CKD patients may play a role in attenuating the rate of the progression of CKD.

SUMMARY

Clinicians should have a low threshold for evaluating diabetic patients with CKD for OSA. Further studies examining if treatment of OSA would improve the outcomes of CKD patients in general and diabetic CKD patients in particular are needed.

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 disordered breathing and cardiovascular risk in older patients initiating dialysis in the United States: a retrospective observational study using medicare data

Background

Sleep disordered breathing (SDB) such as sleep apnea is associated with cardiovascular disease in the general population. However, little is known about the cardiovascular risks of SDB in patients with end-stage renal disease (ESRD).

Methods

We identified Medicare fee-for-service beneficiaries aged ≥67 years initiating dialysis between 2004 and 2009. Outcomes of interest included all-cause mortality, incident myocardial infarction, ischemic stroke, and atrial fibrillation. We compared patients with and without diagnosed SDB using Cox proportional hazards regression.

Results

Between 2004 and 2009, 184,217 older patients developed ESRD, of whom 15,121 (8.2 %) were previously diagnosed with SDB. Patients diagnosed with SDB were younger, more likely to be male and Caucasian, less Medicaid eligible, had more non-Nephrology clinic visits, higher body mass index, and more comorbidity. In analyses adjusting for demographics and BMI, diagnosed SDB was associated with higher risk of death and atrial fibrillation, but not associated with myocardial infarction or ischemic stroke risk. After further adjustment for all baseline characteristics, diagnosed SDB was associated with slightly lower risks of death (hazard ratio [HR]: 0.93, 95 % confidence interval [CI]: 0.91–0.96), myocardial infarction (HR: 0.92, CI: 0.87–0.98), and ischemic stroke (HR: 0.90, 95 % CI: 0.82–0.98), and not associated with atrial fibrillation (HR: 1.02, CI: 0.98–1.07).

Conclusions

In older patients initiating dialysis in the U.S., diagnosed SDB was weakly associated with lower risks of death and important cardiovascular outcomes, thus adding to the list of established risk factors that are paradoxically associated with cardiovascular outcomes in the ESRD population.

Chronic Kidney Disease and Sleeping Disordered Breathing (SDB)

The outlines of the current manuscript are: 1. Re-establish the link between hypertension and SDB including prevalence, mechanism, and reversal of process (i.e. improvement in hypertension with improvement in SDB), why it is important-cardiovascular mortality with numbers. 2. Re-establish the link between hypertension and CKD including same points as above. Then ask if both CKD and SDB are combined, what happens to hypertension and cardiovascular mortality. 3. Lastly, talk about links between CKD and SDB on how each process feeds on the other and is a growing, common problem.

Relationship between dialysis adequacy and sleep quality in haemodialysis patients

AIM AND OBJECTIVES

The aim of this study is to examine the relationship between dialysis adequacy and sleep quality in haemodialysis patients.

BACKGROUND

Sleep problems are common in haemodialysis patients. Dialysis adequacy is one of the factors associated with sleep quality. Studies evaluating the association between dialysis adequacy and sleep quality in haemodialysis patients present different results.

DESIGN

Descriptive and cross-sectional study.

METHODS

This study was performed with a total of 119 patients who had applied to dialysis centres for haemodialysis treatment between January and March 2014. The data collection form consists of socio-demographic and medical characteristics as well as laboratory parameters. A modified Post-Sleep Inventory was used to examine sleep quality in the research.

RESULTS

There were no statistically significant relationship between sleep quality and dialysis adequacy (p > 0·05). When the Post-Sleep Inventory scores were evaluated according to sleep quality, 63·0% of patients had poor sleep quality, and 37·0% had good sleep quality. Sleep quality was worse in unemployed patients (X(2) = 4·852; p = 0·025) and patients who smoked heavily (Z = 2·289; p = 0·022).

CONCLUSIONS

In this study, there is no statistically significant relationship between dialysis adequacy and sleep quality. However, it was found that the majority of haemodialysis patients had poor sleep quality.

RELEVANCE TO CLINICAL PRACTICE

Even if the dialysis adequacy of patients is at the recommended level, their sleep qualities may be poor. Therefore, evaluations of the sleep quality of haemodialysis patients during the clinical practice must be taken into consideration.

Sleep-Disordered Breathing in Patients with Polycystic Liver and Kidney Disease Referred for Transcatheter Arterial Embolization

BACKGROUND AND OBJECTIVES

Sleep-disordered breathing (SDB) is prevalent among patients with CKD, but its prevalence among patients with symptomatic autosomal dominant polycystic kidney disease (ADPKD) and its association with total liver and kidney volume remain unclear.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study examined the association between height-adjusted total liver and kidney volume (htTLKV) and SDB in a cross-sectional study of 304 adult patients with symptomatic ADPKD who were hospitalized at Toranomon Hospital for transcatheter arterial embolization and who underwent pulse oximetry between April 2008 and November 2013. SDB was defined as having a 3% oxygen desaturation index of ≥15 events per hour of sleep. Logistic regression was performed with sex-specific quartiles of htTLKV as the main predictor, using patient data and comorbidities as covariates.

RESULTS

Overall (54.6% women, mean age 56.2±9.4 years, 83.5% on hemodialysis), 177 of 304 patients (58.2%) had SDB. SDB was strongly associated with htTLKV quartiles, demonstrating that odds ratios (ORs) and 95% confidence intervals (95% CIs) for SDB were 1.63 (0.76 to 3.48), 2.35 (1.09 to 5.06), and 4.61 (1.98 to 10.7) for htTLKV quartiles 2-4 (P for trend, P=0.003), respectively. Older age (OR, 1.81 per 10 years; 95% CI, 1.29 to 2.55), male sex (OR, 3.87; 95% CI, 1.96 to 7.66), receiving hemodialysis (OR, 3.46; 95% CI, 1.62 to 12.1), and higher body mass index (≥25 kg/m(2)) (OR, 3.03; 95% CI, 1.08 to 8.52) were also associated with SDB.

CONCLUSIONS

In this highly selected population of patients with symptomatic ADPKD referred for transcatheter arterial embolization, SDB was highly prevalent and independently associated with higher htTLKV.

Relationships Between Malnutrition, Inflammation, Sleep Quality, and Restless Legs Syndrome in Hemodialysis Patients

Restless legs syndrome (RLS) is a common neurologic sensorimotor disorder. It is also seen in hemodialysis patients in whom the mechanism is not thoroughly understood. The aim of this study was to evaluate the association between malnutrition-inflammation score (MIS), sleep quality, and RLS in chronic hemodialysis patients. This cross-sectional study included 232 adult stable chronic hemodialysis patients (mean age 60.9 ± 14.1 years, 56.5% male). RLS frequency, MIS, Pittsburgh Sleep Quality Index (PSQI), laboratory data of patients as well as severity of RLS were evaluated. Thirty-seven patients (15.9%) were diagnosed with RLS. Mean MIS of patients with or without RLS were similar. PSQI of patients with RLS was significantly higher than patients without RLS (P = 0.002). There was a significant positive correlation between RLS severity and PSQI (r = 0.445, P = 0.006). A significant positive correlation was also found between PSQI and MIS in patients with RLS (r = 0.419, P = 0.010). RLS severity was positively correlated with some inflammatory parameters such as white blood cell count and C-reactive protein (r = 0.427, P = 0.008 and r = 0.418 P = 0.010). PSQI was found as an independent significant predictor of RLS (odds ratio [OR] = 1.15 (1.06-1.25), P = 0.001) in multivariate logistic regression analysis. Our study revealed that there was no significant relationship between RLS and MIS in chronic hemodialysis patients. However, RLS severity is correlated with inflammatory parameters. Also, sleep quality in chronic hemodialysis patients with RLS is negatively associated with MIS.

Effects of sleepiness on survival in Japanese hemodialysis patients: J-DOPPS study

Sleep disorder and poor sleep quality are common in chronic hemodialysis (HD) patients. They have been claimed as a cause of morbidity and mortality. The relationship between the degree of sleepiness and survival has not been studied. We studied the degree of sleepiness in 1,252 adult HD patients (age ≥20 years) recruited into the Dialysis Outcomes Practice Pattern Study in Japan (J-DOPPS III), using the Japanese version of the Epworth Sleepiness Scale (JESS) questionnaire. Demographic data were presented for three subgroups: low, intermediate, and high JESS score. Cox proportional hazard regression analysis was performed to estimate the independent effect of several variables on survival. The hazard ratio for mortality was 2.312 (95% CI 1.267-4.220; p = 0.006) for those with a high JESS score (vs. those with a low JESS score) after adjusting for age, vintage (length of time on HD), sex, diabetes, body mass index, cardiovascular disease, HD treatment regimen (time, frequency, and single-pool Kt/V), laboratory data (serum albumin, creatinine, and total cholesterol), and medication (antihypertensive drugs, erythropoietin, vitamin D, and phosphate binders). Patients ≥70 years of age with comorbid conditions (congestive heart failure, stroke, and diabetes) showed a significantly higher JESS score (≥16). The JESS score did not show interaction by age. Results showed that the degree of sleepiness is related to survival in Japanese HD patients, particularly in elderly patients.

Association between Serum Soluble Klotho Levels and Mortality in Chronic Hemodialysis Patients

Klotho is a single-pass transmembrane protein predominantly expressed in the kidney. The extracellular domain of Klotho is subject to ectodomain shedding and is released into the circulation as a soluble form. Soluble Klotho is also generated from alternative splicing of the Klotho gene. In mice, defects in Klotho expression lead to complex phenotypes resembling those observed in dialysis patients. However, the relationship between the level of serum soluble Klotho and overall survival in hemodialysis patients, who exhibit a state of Klotho deficiency, remains to be delineated. Here we prospectively followed a cohort of 63 patients with a mean duration of chronic hemodialysis of 6.7 ± 5.4 years for a median of 65 months. Serum soluble Klotho was detectable in all patients (median 371 pg/mL, interquartile range 309-449). Patients with serum soluble Klotho levels below the lower quartile (<309 pg/mL) had significantly higher cardiovascular and all-cause mortality rates. Furthermore, the higher all-cause mortality persisted even after adjustment for confounders (hazard ratio 4.14, confidence interval 1.29-13.48). We conclude that there may be a threshold for the serum soluble Klotho level associated with a higher risk of mortality.

Death and disability in patients with sleep apnea--a meta-analysis

BACKGROUND

Several studies have been attempting to ascertain the risks of Sleep Apnea Syndrome (SAS) and its morbidity and mortality.

OBJECTIVE

The main objective was to verify whether SAS increases the risk of death; the secondary objective was to evaluate its morbidity in relation to cardiovascular disease and the number of days hospitalized.

METHODS

A systematic review and a meta-analysis were performed of the published literature. The research focused on studies comparing the number of deaths in patients with untreated SAS and in patients with non-SAS.

RESULTS

The meta-analysis was based on 13 articles, corresponding to a total of 13394 participants divided into two groups (non-SAS = 6631; SAS = 6763). The meta-analysis revealed a clear association of SAS with the occurrence of fatal events, where the presence of SAS corresponded to a 61% higher risk of total mortality (OR=1.61; CI: 1.43 - 1.81; p < 0.00001), while the risk of death from cardiac causes was 2.52 times higher in these patients (OR = 2.52; IC: 1.80 - 3.52; p < 0.00001). Similar results were obtained for mortality from other causes (OR = 1.68; CI: 1.08 - 2.61; p = 0.02). Resembling results were obtained in the remaining outcomes: non-fatal cardiovascular events were higher in the SAS group (OR = 2.46; IC: 1.80 - 3.36; p < 0.00001), the average number of days hospitalized was also higher in the SAS group (IV = 18.09; IC: 13.34 - 22.84; p < 0.00001).

CONCLUSION

The results show that untreated SAS significantly increases the risk of death, cardiovascular events and the average number of days hospitalized.

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.

Snoring amplifies the risk of heart failure and mortality in dialysis patients

BACKGROUND

Snoring, an indicator of sleep-disordered breathing (SDB), associates with all-cause and cardiovascular (CV) mortality in high-risk conditions such as chronic heart failure (HF). Because SDB and HF are exceedingly frequent in end-stage kidney disease (ESKD), we hypothesized that SDB as detected by snoring may impact upon the relationship between chronic HF and all-cause and CV mortality in these patients.

METHODS

We tested this hypothesis in a cohort of 827 ESKD patients, followed up for 2.3 years.

RESULTS

In this population, snoring was a strong modifier of the risk of chronic HF for all-cause and CV death. In fully adjusted Cox models, the hazard ratio (HR) associated to chronic HF for the study outcomes was highest in heavy snorers [all-cause death: HR 2.6 (95% CI 1.6-4.3, p < 0.001); CV death: HR 4.0 (95% CI 2.1-7.6, p < 0.001)], intermediate in moderate snorers [all-cause death: HR 1.6 (95% CI 1.1-2.2, p = 0.01); CV death: HR 1.8 (95% CI 1.2-2.8, p = 0.01)], and lowest and not significant in non-snorers [all-cause death: HR 0.9 (95% CI 0.6-1.6, p = NS); CV death: HR 0.8 (95% CI 0.4-1.6, p = NS)].

CONCLUSIONS

Snoring is a strong and independent effect modifier of the relationship between chronic HF and all-cause and CV mortality in ESKD. Since SDB and snoring are in part attributable to reversible pharyngeal oedema, intensified surveillance and treatment of chronic HF snorers on dialysis may translate into better clinical outcomes in this very high-risk population, an issue which remains to be tested in specifically designed clinical trials.

Central sleep apnea

Neurophysiologically, central apnea is due to a temporary failure in the pontomedullary pacemaker generating breathing rhythm. As a polysomnographic finding, central apneas occur in many pathophysiological conditions. Depending on the cause or mechanism, central apneas may not be clinically significant, for example, those that occur normally at sleep onset. In contrast, central apneas occur in a number of disorders and result in pathophysiological consequences. Central apneas occur commonly in high-altitude sojourn, disrupt sleep, and cause desaturation. Central sleep apnea also occurs in number of disorders across all age groups and both genders. Common causes of central sleep apnea in adults are congestive heart failure and chronic use of opioids to treat pain. Under such circumstances, diagnosis and treatment of central sleep apnea may improve quality of life, morbidity, and perhaps mortality. The mechanisms of central sleep apnea have been best studied in congestive heart failure and hypoxic conditions when there is increased CO2 sensitivity below eupnea resulting in lowering eupneic PCO2 below apneic threshold causing cessation of breathing until the PCO2 rises above the apneic threshold when breathing resumes. In many other disorders, the mechanism of central sleep apnea (CSA) remains to be investigated.

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.

Obstructive sleep apnea and cardiovascular risk: meta-analysis of prospective cohort studies

BACKGROUND

Previous studies suggest obstructive sleep apnea (OSA) may increase cardiovascular risk, but the results are inconclusive due to various limitations. We aimed to systematically evaluate the effect of OSA on the incidence of cardiovascular events by a meta-analysis of prospective cohort studies.

METHODS

We searched multiple electronic databases for studies that examined the prospective relationship between OSA and incidence of coronary heart disease (CHD), stroke, or total cardiovascular diseases (CVD) among adults. Either fixed- or random-effects models were used to calculate the pooled risk estimates. Sensitivity analysis was conducted to examine the robustness of pooled outcomes.

RESULTS

Of 17 studies included, 9 reported results on total CVD, 7 reported on fatal or non-fatal CHD, and 10 reported on fatal or non-fatal stroke. The pooled relative risks (95% confidence interval) for individuals with moderate-severe OSA compared with the reference group were 2.48 (1.98-3.10) for total CVD, 1.37 (0.95-1.98) for CHD, and 2.02 (1.40-2.90) for stroke. These results did not materially change in the sensitivity analyses according to various inclusion criteria.

CONCLUSIONS

In conclusion, findings from this meta-analysis supported that moderate-severe OSA significantly increased cardiovascular risk, in particular stroke risk.

Comorbidities and survival in obstructive sleep apnoea beyond the age of 50

BACKGROUND

Although mortality risk associated with obstructive sleep apnoea (OSA) tends to disappear from the age of 50, it has been suggested that OSA treatment by continuous positive airway pressure (CPAP) improves survival even in older subjects. Life expectancy of subjects with several diseases is worse if OSA coexists. The objectives of this study were to evaluate the relevance of comorbidities in the relationship between OSA and mortality, and in the effect of CPAP on survival, in subjects ≥ 50 years old.

METHODS

Data from 810 patients studied by polysomnography for suspected OSA between 1991 and 2000 were retrospectively evaluated. In 2009, state of survival and use of CPAP were enquired. Three hundred and thirteen subjects were < 50 and 497 were ≥ 50 years at diagnosis.

RESULTS

Age and comorbidities, but not apnoea/hypopnoea index (AHI) or lowest nocturnal arterial oxygen saturation (Nadir SaO(2)), predicted mortality in the whole sample. Nadir SaO(2) was related to mortality among the younger subjects without comorbidities (P = 0·01), but not among the older subjects. In the older patients with an AHI > 30 CPAP treatment was associated with a better survival only if comorbidities coexisted.

CONCLUSIONS

Unlike in younger subjects, in subjects ≥ 50 years old, comorbidities do not mask an effect of OSA on mortality. Among OSA subjects ≥ 50 years old, comorbidities could separate those who may expect an improvement in survival with CPAP treatment from those who may not. Possibly, after the age of 50, OSA per se does not affect survival, but worsens prognosis of subjects with coexisting diseases.

Obstructive sleep apnea in incremental hemodialysis: determinants, consequences, and impact on survival

Sleep disorders are common in hemodialysis patients, although causes and consequences remain unclear. We sought to establish prevalence, determinants, and outcomes of sleep disturbances in patients receiving incremental dialysis. One hundred two unselected patients undergoing incremental high-flux hemodialysis or hemodiafiltration underwent limited overnight sleep study. Large subsets underwent echocardiography, interdialytic ambulatory blood pressure monitoring, and brain natriuretic peptide measurements. Patients were followed up to 44 months. Full sleep data were obtained in 91 patients. All had sleep disturbance as evidenced by an apnea-hypopnea index >5/min. We defined major obstructive sleep apnea (MOSA) as an apnea-hypopnea index ≥ 15, together with either significant oxygen desaturation or symptoms of daytime sleepiness. Forty patients met these criteria. Significant independent predictors of MOSA were age <65 years, male gender, has diabetes, and has a brain natriuretic peptide >2500 pg/mL. Mean ambulatory blood pressure and left ventricular mass index were significantly higher in these patients. In a model controlling for body mass index, high C-reactive protein, and the presence of cancer, MOSA was associated with a twofold increased risk of mortality, although this did not reach statistical significance. MOSA was common, and was associated with hypertension and high left ventricular mass index. Whether obstructive sleep apnea contributes to the high mortality remains to be firmly established.

Supine fluid redistribution: should we consider this as an important risk factor for obstructive sleep apnea?

INTRODUCTION

Obstructive sleep apnea (OSA) is a common medical disorder affecting at least 2 % of women and 4 % of men living in Western societies. Obesity, older age, male gender, alcohol and sedative use, smoking, craniofacial parameters, and volume overload are some of the risk factors for this disorder.

DISCUSSION

OSA is a known risk factor complicating the course of arterial hypertension, heart failure, and chronic kidney disease. It is important to note that all of the aforementioned comorbid disorders are associated with volume overload. This explains why patients with OSA and comorbid disorders associated with fluid overload can benefit from treatment with diuretics and drugs modulating the renin-angiotensin-aldosterone system. Additionally, patients with heart failure and high sodium intake are at increased risk for OSA, further supporting the complex interrelationship.

CONCLUSIONS

Hemodialysis and renal transplantation can markedly improve the severity of OSA in patients with concomitant kidney disease. Finally, there is a potential of a vicious cycle between OSA and fluid overload disorders, whereby OSA can contribute to the pathogenesis of arterial hypertension, heart failure, and chronic kidney disease, which in turn will significantly contribute to the course OSA.

The intuitive case for β-blockers in patients with ESRD

Sudden cardiac death (SCD) is common in dialysis patients accounting for up to 25% of all-cause mortality. Unlike in the general population, occlusive coronary artery disease is implicated in a minority of these deaths. Activation of the sympathetic nervous system is prevalent in the dialysis population and may underlie this high rate of SCD. β-blockers reduce SCD in the general population and, given their mode of action, β-blockers would seem to be an ideal class of agents to prevent SCD in dialysis patients. In this review, we will explore the etiology of SCD in dialysis patients and discuss the evidence supporting the use of β-blockers in patients with ESRD. We will also examine potential impediments to the use β-blocker in the dialysis population and outline directions for future trials in this area.

Effect of continuous positive airway pressure on proteinuria in obstructive sleep apnea

Obstructive sleep apnea (OSA) is common in patients with renal disease, and an association between OSA and proteinuria has been proposed. However, the effect on proteinuria of OSA treatment with continuous positive airway pressure (CPAP) is unknown. We experienced a case of severe OSA, where proteinuria was clearly improved after CPAP initiation without any changes of medication or body weight. The remarkable reduction of repetitive apnea and hypopnea by CPAP might ameliorate proteinuria by lessening renal hypoxia and sympathetic nerve activation. This case suggests that CPAP is a promising option for OSA with proteinuria.

Mechanism by which chronic kidney disease causes cardiovascular disease and the measures to manage this phenomenon

In Japan, the number of chronic kidney disease (CKD) patients is thought to be 13,300,000, next in size after those with hypertension and diabetes. Although the number of patients with CKD seems large, it does not mean that all these patients require special treatment. Among them, nephrologists should pay special attention to patients with glomerular filtration rate below 50 mL/min/1.73 m(2) and progressive deterioration of renal function. Treatment of these CKD patients by a limited number of specialists is simply impossible; hence, it is essential to request treatment from physicians who are involved in general internal medicine and primary care. It is well known that not only does CKD cause end-stage renal failure, it also causes the onset of cardiovascular diseases (CVD) such as cardiac infarction and cerebral stroke; however, the question is how much significance does CKD have as a risk factor for CVD. It is understandable that hypertension and CVD are often complications of CKD; however, in addition to what is conventionally mentioned, there are three or four mechanisms that we would like to emphasize, and discuss herein. Among them, we would like to stress the role of klotho genes with special reference to the generation of CVD in CKD patients. When patients develop CKD, it is therefore necessary to remove as far as possible any factors that could represent a risk for CVD. Moreover, by taking appropriate measures against clinical conditions that often complicate CKD, such as hypertension, renal anemia, hyperuricemia, and hyperlipidaemia, the development of CVD can be prevented.