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

Effect of CPAP Therapy on Kidney Function in Patients With Chronic Kidney Disease: A Pilot Randomized Controlled Trial

BACKGROUND

OSA is common in chronic kidney disease (CKD) and may accelerate a decline in kidney function. It is not clear whether treatment of OSA with CPAP improves kidney function.

RESEARCH QUESTION

Does treatment with CPAP improve kidney function in patients with CKD and coexisting OSA?

STUDY DESIGN AND METHODS

A randomized, controlled, nonblinded, parallel clinical trial was performed of patients with stages 3 and 4 CKD and coexisting OSA comparing the effect of CPAP vs usual care on the estimated glomerular filtration rate (eGFR) and the urine albumin to creatinine ratio (ACR) over 12 months.

RESULTS

Fifty-seven patients were enrolled and 30 were randomized to CPAP. They had moderately severe CKD (eGFR, 38.4 ± 1.5 mL/min/1.73 m²) and significant OSA and nocturnal hypoxemia (oxygen desaturation index: 23.9 events/h; interquartile range [IQR], 20.3 events/h; mean peripheral capillary oxygen saturation: 89.5%; IQR, 1.7%); 60% had baseline albuminuria (ACR, > 3 mg/mmol). No significant difference was found between CPAP and usual care in the change in eGFR and ACR over 12 months. Although some improvement in eGFR occurred with CPAP therapy in patients with a lower risk of CKD progression, this did not reach statistical significance.

INTERPRETATION

Although CPAP did not provide additional renal benefits over usual care in all CKD patients, some evidence suggested that CPAP slowed the decline in eGFR in CKD patients with a lower risk of CKD progression. These preliminary data support the need for larger clinical trials exploring the effects of CPAP on kidney function.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT02420184; URL: www.clinicaltrials.gov.

Obstructive sleep apnea in patients with diabetes less than 40 years of age

BACKGROUND AND AIM

Obstructive sleep apnea (OSA) is known to be associated with diabetes mellitus (DM). Age is factor associated with different clinical features of OSA. There is limited data on clinical differences of young DM patients with OSA versus older DM patients with OSA. This study aimed to find clinical differences of DM coexisting with OSA between young age group and older.

METHODS

This is a retrospective, analytical study conducted at Srinagarind Hospital, Thailand. The inclusion criteria were adult patients diagnosed as DM with OSA. The study period was between January 2008 and December 2019. The diagnosis of OSA was made by presence of apnea hypopnea index (AHI) of ≥5 times/hour by polysomnography. Clinical predictors of OSA in young DM patients with age under 40 years were executed.

RESULTS

There were 56 patients in the young diabetes mellitus group, while there were 137 patients in the older diabetes mellitus group. The mean (SD) age of diagnosis for diabetes mellitus of both groups were 31.61 (6.53) and 54.68 (7.62) years, respectively. There were three independent predictors for DM in the young: atrial fibrillation (AF), body mass index (BMI) and glomerular filtration rate (GFR). Presence of AF perfectly predicted DM with OSA in age over 40 years. The adjusted odds ratio for BMI and GFR were 1.29 (95% CI 1.05, 1.58) and 1.06 (1.01, 1.13). The BMI over 32 kg/m² and GFR over 77 ml/min/m² gave sensitivity of 80.00%.

CONCLUSIONS

Young DM patients with OSA had more severe OSA, were more obese, had better renal function, and had fewer AF than the older ones.

A systematic review on the association between obstructive sleep apnea and chronic kidney disease

This systematic review aims to provide a more comprehensive overview of the association between obstructive sleep apnea (OSA) and chronic kidney disease (CKD). A PubMed search was conducted using the terms "(obstructive sleep disorders OR obstructive sleep apnea OR obstructive sleep apnea syndrome) AND (kidney function OR renal outcome OR chronic kidney disease OR end stage renal disease)". Four hundred seventy four articles were initially retrieved, 227 in the last five years. We included articles with similar definitions of OSA, in particular only diagnosed by polysomnography, in order to exclude bias related to different diagnostic clinical tools, prediction algorithms and questionnaires that affected previous studies. Six cross-sectional and two retrospective studies were analyzed. There were a total of 8795 participants across all the studies with a mean age between 51 and 63 years. One study included only males but the proportion of males in the other studies ranged from 58 to 85.6%. The mean body mass index ranged from 25.2 to 32 kg/m2. The majority of studies considered indicate that OSA and CKD are significantly associated, in particular in their more severe categories. It is of great importance to set up a strong clinical collaboration between sleep medicine and nephrology.

Neurologic Manifestations of Systemic Disease: Sleep Disorders

Purpose of review

Sleep is intimately involved in overall health and wellbeing. We provide a comprehensive report on the interplay between systemic diseases and sleep to optimize the outcomes of systemic disorders.

Recent findings

Spanning the categories of endocrinologic disorders, metabolic/toxic disturbances, renal, cardiovascular, pulmonary, gastrointestinal, infectious diseases, autoimmune disorders, malignancy, and critical illness, the review highlights the prevalent coexisting pathology of sleep across the spectrum of systemic disorders. Although it is rare that treating a sleep symptom can cure disease, attention to sleep may improve quality of life and may mitigate or improve the underlying disorder. Recent controversies in assessing the cardiovascular relationship with sleep have called into question some of the benefits of treating comorbid sleep disorders, thereby highlighting the need for an ongoing rigorous investigation into how sleep interplays with systemic diseases.

Summary

Systemic diseases often have sleep manifestations and this report will help the clinician identify key risk factors linking sleep disorders to systemic diseases so as to optimize the overall care of the patient.

Sleep Apnea and the Kidney

Purpose of Review

There are some uncertainties about the interactions between obstructive sleep apnea (OSA) and chronic kidney disease (CKD). We critically reviewed recent studies on this topic with a focus on experimental and clinical evidence of bidirectional influences between OSA and CKD, as well as the effects of treatment of either disease.

Recent Findings

Experimental intermittent hypoxia endangers the kidneys, possibly through activation of inflammatory pathways and increased blood pressure. In humans, severe OSA can independently decrease kidney function. Treatment of OSA by CPAP tends to blunt kidney function decline over time, although its effect may vary. OSA may increase cardiovascular complications and mortality in patients with end-stage renal disease (ESRD), while it seems of little harm after renal transplantation. Excessive fluid removal may explain some of the improvements in OSA severity in ESRD and after transplantation.

Summary

Severe OSA and CKD do interact negatively, mainly through hypoxia and fluid retention. The moderate mutually interactive benefits that treatment of each disease exerts on the other one warrant further studies to improve patient management.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Role of serum periostin in severe obstructive sleep apnea with albuminuria: an observational study

BACKGROUND

Periostin is a matricellular protein and is a useful marker in respiratory diseases. However, the roles of periostin in patients with obstructive sleep apnea (OSA) remain unclear. Several in vitro studies have suggested that mechanical stress, hypoxia, impaired metabolism, and kidney injury, which often accompany OSA, may upregulate the expression of periostin. Meanwhile, serum periostin level has been negatively associated with body mass index (BMI) in the general population. In this study, we hypothesized that a high level of serum periostin despite being overweight/obese may discriminate severe OSA or OSA with comorbidities from mild OSA with obesity alone. We aimed to clarify the roles of periostin in patients with OSA to assist in elucidating the heterogeneity of OSA with comorbidities.

METHODS

Among patients diagnosed as OSA, we examined the associations between serum periostin levels and clinical indices, including the severity of OSA, BMI, and comorbidities, using a multifaceted approach. The serum periostin levels and clinical indices were assessed after 3 months of continuous positive airway pressure (CPAP) treatment.

RESULTS

In 96 patients with OSA, serum periostin level was negatively correlated with BMI, albeit marginally, and tended to be higher in severe OSA than in others when adjusted for BMI. Cluster analysis identified four clusters, including two severe OSA clusters, one of which was characterized by high serum periostin levels and the presence of comorbidities, including albuminuria. In a comparative analysis of severe OSA cases (n = 53), the level of serum-free fatty acids and the frequency of albuminuria were higher in patients with high serum periostin level of ≥87 ng/mL, which was the highest quintile among all participants, than in those with low serum periostin levels (< 87 ng/mL, n = 41). In patients with severe OSA and high serum periostin levels, the levels of serum periostin and urinary albumin significantly decreased after 3 months of CPAP treatment.

CONCLUSIONS

Elevated serum periostin in patients with OSA despite being overweight/obese may be an indicator of severe OSA with comorbidities, particularly albuminuria.

Long-Term Changes in Sleep Disordered Breathing in Renal Transplant Patients: Relevance of the BMI

Sleep disordered breathing (SDB), as defined by the Apnea Hypopnea Index (AHI), is a highly prevalent disturbance in end stage kidney disease. SDB improves early on after renal transplantation but long-term changes in AHI in these patients have not been studied. We studied the long-term changes in AHI in a series of 221 renal transplant patients (mean age: 47 ± 12 years; 70% males) over a median follow up of 35 months. Data analysis was made by the generalized estimating equations method (GEE). On longitudinal observation, the median AHI rose from 1.8 (Interquartile range: 0.6-5.0) to 2.9 (IQR: 1.0-6.6) and to 3.6 (IQR: 1.7-10.4) at the second and third visit, respectively (p = 0.009 by the GEE model and the proportion of patients with moderate to severe SDB rose from 8% to 20%. Longitudinal changes in minimum oxygen saturation (minSaO2) mirrored those in the AHI. In adjusted analyses, repeated measurements of BMI (p < 0.009) emerged as the strongest independent longitudinal correlate of AHI and MinSaO2. The AHI worsens over time in renal transplant patients and longitudinal changes of this biomarker are directly related to simultaneous changes in BMI. Overweight/obesity, a potentially modifiable risk factor, is an important factor underlying the risk of SDB in this population.

Obstructive Sleep Apnea and Circulating Biomarkers of Oxidative Stress: A Cross-Sectional Study

Oxidative stress (OS) drives cardiometabolic diseases. Intermittent hypoxia consistently increases oxidative stress markers. Obstructive sleep apnea (OSA) patients experience intermittent hypoxia and an increased rate of cardiovascular disease, however, the impact of OSA on OS markers is not clear. The objective was to assess relationships between OSA severity and biomarker levels. Patients with suspected OSA referred for a polysomnogram (PSG) provided fasting blood sample. Plasma levels of 8-isoprostane, 8-hydroxydeoxyguanosine (8-OHdG), and superoxide dismutase (SOD) were measured. The relationship between OSA and OS was assessed both before and after controlling for confounders (age, sex, smoking history, history of cardiovascular disease, ethnicity, diabetes, statin usage, body mass index (BMI)). 402 patients were studied (68% male, mean age ± SD = 50.8 ± 11.8 years, apnea-hypopnea index (AHI) = 22.2 ± 21.6 events/hour, BMI = 31.62 ± 6.49 kg/m²⁾. In a multivariable regression, the AHI significantly predicted 8-isoprostane levels (p = 0.0008) together with age and statin usage; AHI was not a predictor of 8-OHdG or SOD. Female sex (p < 0.0001) and no previous history of cardiovascular disease (p = 0.002) were associated with increased antioxidant capacity. Circulating 8-isoprostane levels may be a promising biomarker of the severity of oxidative stress in OSA patients. Prospective studies are needed to determine whether this biomarker is associated with long-term cardiometabolic complications in OSA.

Obstructive sleep apnea syndrome and risk of renal impairment: a systematic review and meta-analysis with trial sequential analysis

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is associated with a variety of systemic diseases. Among patients with chronic kidney diseases (CKD), the prevalence of OSAS is high. OSAS can induce progression of CKD. However, whether or not OSAS can cause renal damage in healthy people is not clear. Thus, the purpose of this meta-analysis was to elucidate whether or not there was an association between OSAS and early renal damage.

METHODS

PubMed, Embase Database, Cochrane Library, Web of Science, China National Knowledge Infrastructure, China Biology Medicine Database, Chinese Scientific Journals Database, and Wanfang Database were searched systematically. The relative risk (RR), weighted mean difference (WMD), and 95% confidence intervals (CI) were used to evaluate the relationship between OSAS and early renal damage. Funnel plot and Egger's test were used to evaluate publication bias, and trial sequential analysis (TSA) was employed to verify the sufficiency of the research conclusions.

RESULTS

A total of 18 studies were analyzed comprising 4,567 participants. Compared with the healthy control group, levels of cystatin C (MD = 0.530, 95% CI 0.423, 0.637, P < 0.01) and proteinuria in patients with OSAS were significantly increased, while the levels of estimated glomerular filtration rate (eGFR) (MD = - 0.194, 95% CI - 0.268, - 0.121, P < 0.01) were significantly decreased. Furthermore, patients with OSAS also had an increased risk of CKD. Subgroup analysis showed that compared with patients without OSAS, the level of serum cystatin C in patients with OSAS was significantly increased independent of hypertension and diabetes, and the eGFR was significantly decreased in patients with moderate to severe OSAS and comorbid hypertension and/or diabetes.

CONCLUSION

In this meta-analysis, OSAS was associated with a higher risk of early renal damage. Patients with OSAS and comorbid hypertension and/or diabetes appear to suffer from severe renal damage.

Predictors of chronic kidney disease in obstructive sleep apnea patients

Introduction

Obstructive sleep apnea (OSA) is a common condition in patients with chronic kidney disease (CKD). It may worsen renal function in CKD patients and is associated with uncontrolled blood pressure. Although OSA is found in up to 80% of CKD patients, there are limited data available on its clinical features in patients with and without CKD.

Objective

This study aimed to identifying the differences in the clinical characteristics of OSA between CKD and non-CKD OSA patients and determine the clinical predictors for CKD in OSA patients.

Methods

This was a retrospective study conducted at Khon Kaen University's Srinagarind Hospital in Thailand between July and December 2018. The inclusion criteria were diagnosis with OSA via polysomnography and having undergone laboratory tests for CKD. Obstructive sleep apnea is diagnosed according to the apnea-hypopnea index (AHI) as experiencing ≥5 events/hour, while CKD diagnosed based on the KDOQI guidelines. Eligible patients were divided into two groups: OSA with CKD and OSA without CKD. Predictors of CKD in OSA patients were analyzed using multivariate logistic regression analysis.

Results

During the study period, there were 178 OSA patients who met the study criteria, 88 (49.44%) of whom were in the OSA with CKD group. Both age and body mass index were comparable between OSA patients with CKD and those without (age: 59 and 57 years, respectively; body mass index: 30 and 29 kg/m², respectively. There were three significant factors that differed between those with and without CKD group including systolic blood pressure (147 vs 135 mmHg), proportion of patients with diabetes (55% vs 34%), and proportion of patients with Mallampati scores of 3-4 (73% vs 39%). There were three independent predictors for OSA in patients with CKD: female sex, high systolic blood pressure, and Mallampati score of 3 or 4, with adjusted odds ratios (95% confidence interval) of 4.624 (1.554, 13.750), 1.060 (1.020, 1.101), and 2.816 (1.356, 5.849), respectively. The Hosmer-Lemeshow chi-square statistic of the predictive model was 6.06 (p 0.640). Systolic blood pressure of more than 130 and 150 mmHg resulted in sensitivity of 84.21% and specificity of 81.40%, respectively.

Conclusions

Female sex, high systolic blood pressure, and Mallampati score of 3-4 were suggestive of OSA with CKD. Obstructive sleep apnea patients with one or more of these predictors may have a high risk of CKD.

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.

Losartan protects against intermittent hypoxia-induced peritubular capillary loss by modulating the renal renin-angiotensin system and angiogenesis factors

Obstructive sleep apnea is characterized by chronic intermittent hypoxia (CIH), which is a risk factor for renal peritubular capillary (PTC) loss, and angiotensin II receptor blockers can alleviate PTC loss. However, the mechanism by which losartan (an angiotensin II receptor blocker) reduces CIH-induced PTC loss and attenuates kidney damage is still unknown. Thus, in this study, we examined the protective effects of losartan against CIH-induced PTC loss and explored the underlying mechanisms in rat CIH model. The immunohistochemical staining of CD34 and morphological examination showed that CIH reduced PTC density and damaged tubular epithelial cells. Immunohistochemistry, enzyme-linked immunosorbent assay (ELISA), real-time quantitative PCR, and western blot analysis results revealed that CIH increased the expression of hypoxia inducible factor-1α (HIF-1α), angiotensin II (Ang II), angiotensin II type 1 receptor (AT1R), pro-angiogenesis factor vascular endothelial growth factor (VEGF), and anti-angiogenesis factor thrombospondin-1 (TSP-1) in the renal cortex of rats. CIH may up-regulate VEGF expression and simultaneously increase TSP-1 production. By histopathological, immunohistochemistry, ELISA, RT-qPCR, and western blot analysis, we found that the expressions of renal renin-angiotensin system (RAS), HIF-1α, VEGF, and TSP-1 were decreased, and PTC loss and tubular epithelial cell injury were attenuated with losartan treatment. Losartan ameliorated CIH-induced PTC loss by modulating renal RAS to improve the crosstalk between endothelial cells and tubular epithelial cells and subsequently regulate the balance of angiogenesis factors. Our study provided novel insights into the mechanisms of CIH-induced kidney damage and indicated that losartan could be a potential therapeutic agent for renal protection by alleviating CIH-induced PTC loss.

Trastornos del sueño en el paciente con enfermedad renal crónica avanzada

Objetivo: Conocer las alteraciones y/o trastornos del sueño en los pacientes con Enfermedad Renal Crónica Avanzada. Método: Se realizó una búsqueda en las bases de datos Google Académico, Scielo, Science Direct, PubMed y Scopus. Se incluyeron artículos científicos en español e inglés y texto completo disponible. Se analizaron aquellos artículos que trataban sobre alteraciones del sueño en los pacientes en prediálisis, y en tratamiento renal sustitutivo: Hemodiálisis, Diálisis Peritoneal y Trasplante Renal. Resultados: Se han incluido 30 artículos publicados entre los años 2013 y 2018. Los pacientes con Enfermedad Renal Crónica Avanzada presentan una alta prevalencia de alteraciones del sueño, llegando a alcanzar una prevalencia de casi el 90% en pacientes en hemodiálisis y diálisis peritoneal, y 62% en pacientes con trasplante renal; y entre el 44% y el 77% en la etapa prediálisis. Las alteraciones del sueño más frecuentes encontradas, fueron: insomnio, síndrome de piernas inquietas, apnea del sueño y somnolencia diurna excesiva. Como principales medidas y tratamientos utilizados para las alteraciones del sueño en estos pacientes se han encontrado terapias tanto farmacológicas, como no farmacológicas y la combinación de ambas. Conclusiones: Las alteraciones del sueño tienen una alta prevalencia en los pacientes con Enfermedad Renal Crónica Avanzada, tanto en prediálisis como en tratamiento renal sustitutivo; siendo las más frecuentes el insomnio, el síndrome de piernas inquietas, la apnea obstructiva del sueño y la somnolencia diurna excesiva. Entre los factores de riesgo más influyentes destacan: ansiedad y depresión, Diabetes Mellitus, hipertensión arterial, problemas respiratorios y tiempo en diálisis.

Sleep apnea and kidney transplant outcomes: findings from a 20-year (1997-2017) historical cohort study

OBJECTIVE/BACKGROUND

A historic cohort single-center study of kidney transplant recipients with graft loss examined the associations between sleep apnea and two transplant outcomes, death with a functioning graft (DWFG), and graft survival time.

PATIENT/METHODS

Adult patients who received transplants and experienced graft failure or DWFG from January 1, 1997 to January 1, 2017 constituted the cohort (n = 322). Data for the study were obtained by merging two secondary data sources: the Organ Procurement and Transplantation Network (OPTN) database and the transplant center's medical records. A Cox regression modeled the association of diagnosed sleep apnea, stratified by year-of transplant surgery, with graft survival time. Using backward elimination, this model was adjusted for recipient age, race/ethnicity, gender, functional status, donor age, and antigen mismatch.

RESULTS

No statistically significant differences were found for proportions of DWFG in those with, versus without, sleep apnea, informing our censoring approach. When examining graft survival time, the Cox regression model was stratified given a sleep apnea and year-of-transplant interaction (p < 0.01, adjusted model). For patients transplanted between 1997 and 2008, sleep apnea was statistically significantly associated with a decreased risk of graft failure or cardiovascular-related DWFG [adjusted Hazard Ratio (aHR) = 0.63, 95%CI, 0.42-0.94]. For patients transplanted between 2009 and 2017, sleep apnea statistically significantly increased the risk of graft failure or cardiovascular-related DWFG (aHR = 2.61, 95%CI, 1.13-6.00).

CONCLUSIONS

In a cohort of transplant recipients with graft loss, sleep apnea increased the risk of graft loss nearly three-fold among patients transplanted between 2009 and 2017. Similar DWFG proportions by sleep apnea presence indicate this risk is likely driven by renal failure, not mortality. Further research on whether treatment of sleep apnea can improve graft survival is warranted.

Obstructive sleep apnea and hypertension in pediatric chronic kidney disease

BACKGROUND

Children with chronic kidney disease (CKD) are at risk for obstructive sleep apnea (OSA) and hypertension. The objectives of this study were to explore associations between OSA severity using the apnea-hypopnea-index(AHI) and obstructive apnea-hypopnea-index(OAHI) on polysomnography (PSG), OSA symptoms, and measures of hypertension in children with CKD.

METHODS

One-night in-laboratory PSGs and 24-h ambulatory blood pressure monitoring (ABPM) were performed on children with CKD stages 2-5 (non-dialysis dependent). Sleep questionnaires, including the modified Epworth Sleepiness Scale (ESS) and the Pediatric Sleep Questionnaire (PSQ), were administered during the sleep study.

RESULTS

Nineteen children and adolescents completed a PSG and questionnaires and thirteen completed ABPMs. Mean (standard deviation) age at the time of the sleep study was 14.1 (3.2) years. Eleven (58%) participants had CKD stage two, and eight (42%) had stage 3-4. None of the participants were found to have OSA on PSG. One participant had a positive ESS score (≥ 11) and five participants had positive PSQ scores (≥  eight). Night systolic and diastolic pressures were strongly correlated with the OAHI (r = 0.67 and r = 0.69, respectively, p < 0.05), while the AHI was not correlated with any blood pressure measures.

CONCLUSIONS

Our study did not find OSA on PSG in children with predominantly mild to moderate CKD. The OAHI was found to be strongly correlated with nighttime blood pressures. Future prospective studies with a larger sample size are needed to monitor for potential progression of symptoms and findings on PSG in pediatric patients as they evolve across the spectrum of CKD.

Risk factors of sleep-disordered breathing in haemodialysis patients

Background

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

Methods

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

Results

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

Conclusion

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

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.

Clinical characteristics of snoring patients with primary aldosteronism and obstructive sleep apnea-hypopnea syndrome

The 2016 guideline on the work-up of primary aldosteronism recommended that patients with obstructive sleep apnea–hypopnea syndrome (OSAS) be screened. This study aimed to identify the clinical characteristics of snoring patients with primary aldosteronism (PA) complicated by OSAS. Sixty-eight self-reported or witnessed snoring patients and 609 non-snoring patients diagnosed with PA between 2010 and 2015 were recruited in this retrospective study. Compared to non-snoring patients, snoring patients had significantly (P < 0.05) higher body mass index (BMI), diastolic blood pressure (DBP), and serum and urinary sodium, as well as lower estimated glomerular filtration rate (eGFR). Moreover, snoring patients exhibited significantly (P < 0.01) higher plasma renin activity levels and lower plasma aldosterone levels and aldosterone-to-renin activity ratios (ARRs) than patients with PA alone. When age, sex, duration of hypertension, and BMI were matched between groups, snoring patients still showed significantly (P < 0.05) higher plasma renin activity, serum and urinary sodium, and lower ARR and eGFR than those in the PA-only group. All 68 snoring patients underwent polysomnography, with 7 having mild (apnea–hypopnea index (AHI) ≥ 5 and <15), 21 moderate (AHI ≥ 15 and <30), and 40 severe (AHI ≥ 30) OSAS. The BMI of patients with OSAS was negatively correlated with the lowest SaO₂ (r = −0.318, P = 0.018) but not with the AHI. In conclusion, snoring patients with PA tend to have increased BMI and DBP, as well as decreased eGFR and ARR. Snoring patients with PA had higher prevalence of moderate-to-severe OSAS.

Obstructive sleep apnea and comorbidities: a dangerous liaison

Obstructive sleep apnea (OSA) is a highly prevalent disease, and is traditionally associated with increased cardiovascular risk. The role of comorbidities in OSA patients has emerged recently, and new conditions significantly associated with OSA are increasingly reported. A high comorbidity burden worsens prognosis, but some data suggest that CPAP might be protective especially in patients with comorbidities. Aim of this narrative review is to provide an update on recent studies, with special attention to cardiovascular and cerebrovascular comorbidities, the metabolic syndrome and type 2 diabetes, asthma, COPD and cancer. Better phenotypic characterization of OSA patients, including comorbidities, will help to provide better individualized care. The unsatisfactory adherence to CPAP in patients without daytime sleepiness should prompt clinicians to examine the overall risk profile of each patient in order to identify subjects at high risk for worse prognosis and provide the optimal treatment not only for OSA, but also for comorbidities.

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.

Renal cortical oxygen tension is decreased following exposure to long-term but not short-term intermittent hypoxia in the rat

Chronic kidney disease (CKD) occurs in more than 50% of patients with obstructive sleep apnea (OSA). However, the impact of intermittent hypoxia (IH) on renal function and oxygen homeostasis is unclear. Male Sprague-Dawley rats were exposed to IH (270 s at 21% O₂; 90 s hypoxia, 6.5% O₂ at nadir) for 4 h [acute IH (AIH)] or to chronic IH (CIH) for 8 h/day for 2 wk. Animals were anesthetized and surgically prepared for the measurement of mean arterial pressure (MAP), and left renal excretory function, renal blood flow (RBF), and renal oxygen tension (Po₂). AIH had no effect on MAP (123 ± 14 vs. 129 ± 14 mmHg, means ± SE, sham vs. IH). The CIH group was hypertensive (122 ± 9 vs. 144 ± 15 mmHg, P < 0.05). Glomerular filtration rate (GFR) (0.92 ± 0.27 vs. 1.33 ± 0.33 ml/min), RBF (3.8 ± 1.5 vs. 7.2 ± 2.4 ml/min), and transported sodium (TNa) (132 ± 39 vs. 201 ± 47 μmol/min) were increased in the AIH group (all P < 0.05). In the CIH group, GFR (1.25 ± 0.28 vs. 0.86 ± 0.28 ml/min, P < 0.05) and TNa (160 ± 39 vs. 120 ± 40 μmol/min, P < 0.05) were decreased, while RBF (4.13 ± 1.5 vs. 3.08 ± 1.5 ml/min) was not significantly different. Oxygen consumption (QO₂) was increased in the AIH group (6.76 ± 2.60 vs. 13.60 ± 7.77 μmol/min, P < 0.05), but it was not significantly altered in the CIH group (3.97 ± 2.63 vs. 6.82 ± 3.29 μmol/min). Cortical Po₂ was not significantly different in the AIH group (46 ± 4 vs. 46 ± 3 mmHg), but it was decreased in the CIH group (44 ± 5 mmHg vs. 38 ± 2 mmHg, P < 0.05). For AIH, renal oxygen homeostasis was preserved through a maintained balance between O₂ supply (RBF) and consumption (GFR). For CIH, mismatched TNa and QO₂ reflect inefficient O₂ utilization and, thereby, sustained decrease in cortical Po₂.

Risk, Severity, and Predictors of Obstructive Sleep Apnea in Hemodialysis and Peritoneal Dialysis Patients

Our study aimed to determine the incidence and severity of obstructive sleep apnea (OSA) in patients with end-stage renal disease (ESRD) and also whether different dialysis modalities confer different risk and treatment response for OSA. We used Taiwan's National Health Insurance Research Database for analysis and identified 29,561 incident dialysis patients as the study cohort between 2000 and 2011. Each dialysis patient was matched with four non-dialysis control cases by age, sex, and index date. Cox regression hazard models were used to identify the risk of OSA. The incidence rate of OSA was higher in the peritoneal dialysis (PD) cohort than the hemodialysis (HD) and control cohort (18.9, 7.03 vs. 5.5 per 10,000 person-years, respectively). The risk of OSA was significantly higher in the PD (crude subhazard ratio (cSHR) 3.50 [95% CI 2.71⁻4.50], p < 0.001) and HD cohort (cSHR 1.31 [95% CI 1.00⁻1.72], p < 0.05) compared with the control cohort. Independent risk factors for OSA in this population were age, sex, having coronary artery disease (CAD), hyperlipidemia, chronic obstructive pulmonary disease (COPD), and hypertension. Major OSA (MOSA) occurred in 68.6% in PD and 50.0% in HD patients with OSA. In the PD subgroup, the incidence of mortality was significantly higher in OSA patients without continuous positive airway pressure (CPAP) treatment compared with OSA patients undergoing CPAP treatment. The results of this study indicate that ESRD patients were at higher risk for OSA, especially PD patients, compared with control. The severity of OSA was higher in PD patients than HD patients. Treatment of MOSA with CPAP was associated with reduced mortality in PD patients.

Obstructive sleep apnoea and the risk for coronary heart disease and type 2 diabetes: a longitudinal population-based study in Finland

OBJECTIVE

To evaluate if obstructive sleep apnoea (OSA) modifies the risk of coronary heart disease, type 2 diabetes (T2D) and diabetic complications in a gender-specific fashion.

DESIGN AND SETTING

A longitudinal population-based study with up to 25-year follow-up data on 36 963 individuals (>500 000 person years) from three population-based cohorts: the FINRISK study, the Health 2000 Cohort Study and the Botnia Study.

MAIN OUTCOME MEASURES

Incident coronary heart disease, diabetic kidney disease, T2D and all-cause mortality from the Finnish National Hospital Discharge Register and the Finnish National Causes-of-Death Register.

RESULTS

After adjustments for age, sex, region, high-density lipoprotein (HDL) and total cholesterol, current cigarette smoking, body mass index, hypertension, T2D baseline and family history of stroke or myocardial infarction, OSA increased the risk for coronary heart disease (HR=1.36, p=0.0014, 95% CI 1.12 to 1.64), particularly in women (HR=2.01, 95% CI 1.31 to 3.07, p=0.0012). T2D clustered with OSA independently of obesity (HR=1.48, 95% CI 1.26 to 1.73, p=9.11×[Formula: see text]). The risk of diabetic kidney disease increased 1.75-fold in patients with OSA (95% CI 1.13 to 2.71, p=0.013). OSA increased the risk for coronary heart disease similarly among patients with T2D and in general population (HR=1.36). All-cause mortality was increased by OSA in diabetic individuals (HR=1.35, 95% CI 1.06 to 1.71, p=0.016).

CONCLUSION

OSA is an independent risk factor for coronary heart disease, T2D and diabetic kidney disease. This effect is more pronounced even in women, who until now have received less attention in diagnosis and treatment of OSA than men.

Telmisartan attenuates kidney apoptosis and autophagy-related protein expression levels in an intermittent hypoxia mouse model

Purpose

Obstructive sleep apnea (OSA) is associated with renal impairs. As a novel pathophysiological hallmark of OSA, chronic intermittent hypoxia (CIH) enhances apoptosis and autophagy. The present study aims to evaluate the effect of telmisartan on CIH-induced kidney apoptosis and autophagy in a mouse model of OSA.

Materials and methods

Mice were randomly allocated to normoxia, CIH, and CIH+telmisartan groups (n = 12 in each group). The CIH exposure duration was 12 weeks. Mice in the CIH+telmisartan group received telmisartan administration. The terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay and western blotting of Bax and cleaved caspase-3 were conducted for evaluating apoptosis in kidney tissue. While the autophagy-related proteins, beclin-1 and LC3, were also observed via western blotting.

Results

The percentage of apoptotic cell in the CIH group was significantly higher than that of normoxia group; meanwhile, Bax and cleaved caspase-3 protein levels were increased in the CIH group than those of normoxia group (all p < 0.05). Compared with the normoxia group, mice in the CIH group had greater autophagy-related proteins (beclin-1 and LC3) expression. When compared to the CIH group, both the renal apoptosis and autophagy in the CIH+telmisartan group were decreased.

Conclusion

The CIH accelerates renal apoptosis and autophagy levels. Telmisartan ameliorating those levels suggests that it might prevent renal impairs from the CIH in OSA patients.

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.

Serum levels of NGAL and cystatin C as markers of early kidney dysfunction in patients with obstructive sleep apnea syndrome

PURPOSE

Obstructive sleep apnea syndrome (OSAS) has been recently proposed as an independent risk factor for chronic kidney disease. Cystatin C (Cyst C) and neutrophil gelatinase-associated lipocalin (NGAL) are novel biomarkers for the earlier detection of latent kidney disease. The aim of the study was to assess serum Cyst C and NGAL levels in otherwise healthy OSAS patients and to explore possible associations with sleep parameters.

METHODS

Consecutive subjects (n = 96, 79.2% males), without known comorbidities, with symptoms suggestive of OSAS were included. All of them underwent polysomnography (PSG) and blood examination for the measurement of serum Cyst C and NGAL levels.

RESULTS

Based on apnea-hypopnea index (AHI), subjects were classified into two groups: 32 controls and 64 OSAS patients, with no significant differences in terms of age (50.1 ± 11.7 vs 51 ± 12.2 years, p = 0.747) and BMI (33.9 ± 8.8 vs 35.9 ± 13.1 kg/m², p = 0.449). Serum Cyst C and NGAL mean levels were higher in OSAS patients compared to those in controls (1155.2 ± 319.3 vs 966.8 ± 173 ng/ml, p = 0.001, and 43.7 ± 23.2 vs 35.6 ± 13.8 ng/ml, p = 0.035, respectively). After adjustment for age and BMI in OSAS patients, serum NGAL levels were associated with AHI (β = 0.341, p = 0.015) and minimum oxyhemoglobin saturation during sleep (β = - 0.275, p = 0.032), while serum Cyst C levels were associated with percentage of time with oxyhemoglobin saturation < 90% (β = 0.270, p = 0.043), average (β = - 0.308, p = 0.018), and minimum (β = - 0.410, p = 0.001) oxyhemoglobin saturation during sleep.

CONCLUSIONS

Higher risk for latent kidney disease in otherwise healthy OSAS patients is indicated. Sleep hypoxia seems to be a significant contributor in the pathogenetic process of renal dysfunction in OSAS.

Residual Renal Function and Obstructive Sleep Apnea in Peritoneal Dialysis: A Pilot Study

PURPOSE

Obstructive sleep apnea is common in patients with end-stage renal disease, and there is increasing evidence that clinical factors specific to end-stage renal disease contribute pathophysiologically to obstructive sleep apnea. It is not known whether circumstances specific to dialysis modality, in this case peritoneal dialysis, affect obstructive sleep apnea. Our study aimed to investigate the prevalence of obstructive sleep apnea in the peritoneal dialysis population and the relevance of dialysis-specific measures and kidney function in assessing this bidirectional relationship.

METHODS

Participants with end-stage renal disease who were treated with nocturnal automated peritoneal dialysis for at least 3 months were recruited from a hospital-based dialysis center. Laboratory measures of dialysis adequacy, peritoneal membrane transporter status, and residual renal function were gathered by chart review. Patients participated in a home sleep apnea test using a level III sleep apnea monitor.

RESULTS

Of fifteen participants recruited, 33% had obstructive sleep apnea diagnosed by apnea-hypopnea index ≥ 5 events per hour of sleep. Renal creatinine clearance based upon 24-h urine collection was negatively correlated with apnea-hypopnea index (ρ = - 0.63, p = 0.012). There were no significant associations between anthropometric measures, intra-abdominal dwell volume, or peritoneal membrane transporter status and obstructive sleep apnea measures.

CONCLUSIONS

The prevalence of obstructive sleep apnea and sleep disturbances is high in participants receiving peritoneal dialysis. Elevated apnea-hypopnea index is associated with lower residual renal function, whereas dialysis-specific measures such as intra-abdominal dwell volume and peritoneal membrane transporter status do not correlate with severity of obstructive sleep apnea.

Continuous Positive Airway Pressure Reduces Night-Time Blood Pressure and Heart Rate in Patients With Obstructive Sleep Apnea and Resistant Hypertension: The RHOOSAS Randomized Controlled Trial

Objective

Most patients with resistant hypertension (RH) have obstructive sleep apnea (OSA). We aimed to determine the impact of OSA and continuous positive airway pressure (CPAP) treatment on the leptin profile and blood pressure (BP) in patients with RH.

Methods

After an initial case-control study (RH with and without OSA), we performed a randomized, single blind study in OSA + RH patients receiving either sham CPAP (3 months) followed by active CPAP (6 months) or 6 months of active CPAP. The primary outcome was the comparison of leptin levels between groups of RH patients with or without OSA. Secondary outcomes were the comparison of metabolic parameters, biomarkers of sympathetic activity, and BP indices between the two groups of RH patients with or without OSA. The same outcomes were then evaluated and compared before and after sham and effective CPAP intervention.

Results

Sixty-two patients (60 ± 10 years; 77% men) with RH (24-h daytime systolic BP (SBP)/diastolic BP: 145 ± 13/85 ± 10 mmHg, 3.7 antihypertensive drugs) were included. The 37 RH patients exhibiting OSA (60%) were predominantly men (87 vs 64% for non-OSA patients), with a greater prevalence of metabolic syndrome and higher creatininemia. Their leptin concentrations were significantly lower than in non-OSA patients [9 (6; 15) vs 17 (6; 29) ng/mL] but increased after 6 months of CPAP. Three months of effective CPAP significantly decreased night-time SBP by 6.4 mmHg and heart rate (HR) by 6.0 bpm, compared to sham CPAP.

Conclusion

The association between OSA and RH corresponds to a specific, predominately male phenotype with a higher burden of metabolic syndrome and higher creatininemia but there was no significant difference between OSA and non-OSA patients regarding BP indices, and the number of antihypertensive drugs used. Active CPAP could be efficient at decreasing night-time BP and HR, but there was no difference between CPAP and sham CPAP groups for all metabolic and SNS markers (NCT00746902 RHOOSAS).

Intermittent hypoxia causes histological kidney damage and increases growth factor expression in a mouse model of obstructive sleep apnea

Epidemiological studies demonstrate an association between obstructive sleep apnea (OSA) and accelerated loss of kidney function. It is unclear whether the decline in function is due to OSA per se or to other confounding factors such as obesity. In addition, the structural kidney abnormalities associated with OSA are unclear. The objective of this study was to determine whether intermittent hypoxia (IH), a key pathological feature of OSA, induces renal histopathological damage using a mouse model. Ten 8-week old wild-type male CB57BL/6 mice were randomly assigned to receive either IH or intermittent air (IA) for 60 days. After euthanasia, one kidney per animal was paraformaldehyde-fixed and then sectioned for histopathological and immunohistochemical analysis. Measurements of glomerular hypertrophy and mesangial matrix expansion were made in periodic acid–Schiff stained kidney sections, while glomerular transforming growth factor-β1 (TGF-β1), connective tissue growth factor (CTGF) and vascular endothelial growth factor-A (VEGF-A) proteins were semi-quantified by immunohistochemistry. The antigen-antibody reaction was detected by 3,3′-diaminobenzidine chromogen where the color intensity semi-quantified glomerular protein expression. To enhance the accuracy of protein semi-quantification, the percentage of only highly-positive staining was used for analysis. Levels of TGF-β, CTGF and VEGF-A proteins in the kidney cortex were further quantified by western blotting. Cellular apoptosis was also investigated by measuring cortical antiapoptotic B-cell lymphoma 2 (Bcl-2) and apoptotic Bcl-2-associated X (Bax) proteins by western blotting. Further investigation of cellular apoptosis was carried out by fluorometric terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling (TUNEL) staining. Finally, the levels of serum creatinine and 24-hour urinary albumin were measured as a general index of renal function. Our results indicate that mice exposed to IH have an increased glomerular area (by 1.13 fold, p< 0.001) and expansion of mesangial matrix (by 1.8 fold, p< 0.01). Moreover, the glomerular expressions of TGF-β1, CTGF and VEGF-A proteins were 2.7, 2.2 and 3.8-fold higher in mice exposed to IH (p< 0.05 for all). Furthermore, western blotting protein analysis demonstrates that IH-exposed mice express higher levels of TGF-β1, CTGF and VEGF-A proteins by 1.9, 4.0 and 1.6-fold (p< 0.05 for all) respectively. Renal cellular apoptosis was greater in the IH group as shown by an increased cortical Bax/Bcl-2 protein ratio (p< 0.01) and higher fluorometric TUNEL staining (p< 0.001). Finally, 24-hr urinary albumin levels were higher in mice exposed to IH (43.4 μg vs 9.7 μg, p< 0.01), while there were no differences in serum creatinine levels between the two groups. We conclude that IH causes kidney injury that is accompanied by glomerular hypertrophy, mesangial matrix expansion, increased expression of glomerular growth factors and an increased cellular apoptosis.

Risk of glomerular filtration rate decline in patients with hypertrophic cardiomyopathy and obstructive sleep apnoea

Sleep apnoea is associated with chronic kidney diseases. A high obstructive sleep apnoea (OSA) prevalence is shown in patients with hypertrophic cardiomyopathy (HCM). Whether the presence of OSA would affect the renal function of patients with HCM is unknown. Forty-five consecutive patients with HCM were divided into the HCM OSA− and OSA+ groups. Forty-three patients with OSA without HCM were recruited as controls. Clinical indices, including estimated glomerular filtration rate (eGFR) and urine 8-hydroxy-2-deoxyguanosine (8-OHdG), were measured. The eGFR was significantly lower in the HCM OSA+ group than in the HCM OSA− (P < 0.05) and OSA (P < 0.001) groups. Multivariate linear regression analysis identified that the apnoea-hypopnoea index was independently associated with eGFR in all patients with HCM (β = −1.329, 95% confidence interval: −1.942, −0.717, P < 0.001). The urine 8-OHdG level, an oxidative stress marker, was significantly higher in the HCM OSA+ group than in the HCM OSA− (P < 0.001) and OSA (P < 0.001) groups and significantly correlated with the AHI (r = 0.467, P = 0.003) and eGFR (r = −0.457, P = 0.004) in all patients with HCM. Our study suggests a risk of eGFR decline in patients with HCM and OSA.

Chronic intermittent hypoxia exposure induces kidney injury in growing rats

OBJECTIVE

The objectives of this paper are to examine the effect of chronic intermittent hypoxia (CIH) on the morphological changes in the kidney of growing rats and to explore the mechanisms underlying the CIH-induced renal damage.

METHODS

Forty Sprague-Dawley rats were randomly divided into two groups: 2 and 4 weeks CIH groups (2IH, 4IH), and in the control group 2 and 4 weeks air-stimulated groups (2C, 4C), with 10 rats in each group. Pathological changes of renal tissue were observed by HE staining, PAS staining, and Masson staining. Real-time PCR method was used to detect the mRNA expression of HIF-1α, CuZnSOD/ZnSOD, and MnSOD in renal tissue.

RESULTS

(1) Intermittent hypoxia (IH) caused morphological damage in the kidney. Hypertrophy of epithelial cells in the kidney tubules and dilation in the glomeruli were observed under light microscope in HE and PAS stain, especially in 4IH group. Masson staining showed no significant fibrotic response in the IH groups. (2) Compared with the corresponding control groups, the levels of serum SOD were significantly lower in CIH groups, and especially in 4IH group. The mRNA expression of Cu/ZnSOD and MnSOD in CIH groups decreased significantly as compared to control groups. The mRNA levels of HIF-1α in the kidney were significantly higher in CIH groups than those in the corresponding control groups.

CONCLUSION

Oxidative stress played a critical role in renal damage by up-regulating HIF-1α transcription and down-regulating Cu/ZnSOD and MnSOD transcription after chronic intermittent hypoxia exposure in growing rats.

Association of sleep-disordered breathing with diabetes-associated kidney disease

INTRODUCTION

Diabetes-associated kidney disease is characterized by impairment of renal function and albuminuria. The aim of the present study was to assess whether sleep-disordered breathing is associated with decreased estimated glomerular filtration rate or increased urine-albumin-to-creatinine-ratio independently from known modulators of diabetes-associated kidney disease.

MATERIAL AND METHODS

Estimated glomerular filtration rate and urine-albumin-to-creatinine-ratio were determined in the baseline survey of the DIACORE-SDB substudy, a prospectively planned study of Diabetes mellitus 2 patients. As a measure of the severity of sleep-disordered breathing, the apnea-hypopnea-index was assessed using a 2-channel ambulatory SDB-monitoring device.

RESULTS

A total of 679 patients (mean age 66 years, men 61%, mean body-mass-index 31.2 kg/m²) were analyzed. In multivariable linear regression models adjusting for known modulators of diabetes-associated kidney disease, such as sex, age, body-mass-index, systolic blood pressure, duration of diabetes and HbA1c, apnea-hypopnea-index [beta-estimate -0.2 ml/min/1.73 m², 95% CI (-0.3; -0.1), p = .004], duration of diabetes and age were associated with estimated glomerular filtration rate. Apnea-hypopnea-index [beta-estimate 0.01 mg/g, 95% CI (0.00; 0.02), p = .009], duration of diabetes, HbA1c and systolic blood pressure were associated with ln(urine-albumin-to-creatinine-ratio).

CONCLUSION

In patients with diabetes mellitus type 2, more severe sleep-disordered breathing is significantly associated with lower estimated glomerular filtration rate and increased albuminuria, independent of known modulators of diabetes-associated kidney disease.

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.

Blood Pressure and Metabolic Changes After 3-Month CPAP Therapy in a Very Elderly Obese with Severe Obstructive Sleep Apnea: A Case Report and Review of the Literature

Age is one of the main risk factor for the presence of obstructive sleep apnea (OSA). This syndrome is associated with hypertension, cardiovascular disease, cognitive impairment and metabolic abnormalities, such as type 2 diabetes. Continuous positive airway pressure (CPAP) represents the gold standard therapy, but its benefit is still to be determined in very elderly. We report the blood pressure and metabolic changes in a very elderly obese with severe OSA after 3-month CPAP therapy. We have evaluated a very elderly obese male affected by severe symptomatic OSA, poor controlled nocturnal hypertension and insulin resistance. After 3-month CPAP therapy, without any changes in drug therapy, we observed a normalization of circadian blood pressure (BP) pattern, an improved insulin sensitivity, together with a reduced resting energy expenditure, despite no significant change in weight. This case report shows the benefits of OSA treatment with CPAP, not only on BP profile, but also on metabolic parameters in a very elderly, a particular type of patient in which scientific evidence is still scant. Further studies are needed to better investigate the relationship between OSA, CPAP therapy and energy expenditure not only in adults but also in elderly patients.

Angiotensin-(1-7) relieved renal injury induced by chronic intermittent hypoxia in rats by reducing inflammation, oxidative stress and fibrosis

We aimed to study the renal injury and hypertension induced by chronic intermittent hypoxia (CIH) and the protective effects mediated by angiotensin 1-7 [Ang(1-7)]. We randomly assigned 32 male Sprague-Dawley rats (body weight 180-200 g) to normoxia control, CIH, Ang(1-7)-treated normoxia, and Ang(1-7)-treated CIH groups. Systolic blood pressure (SBP) was monitored at the start and end of each week. Renal sympathetic nerve activity (RSNA) was recorded. CTGF and TGF-β were detected by immunohistochemistry and western blotting. Tissue parameters of oxidative stress were also determined. In addition, renal levels of interleukin-6, tumor necrosis factor-α, nitrotyrosine, and hypoxia-inducible factor-1α were determined by immunohistochemistry, immunoblotting, and ELISA. TUNEL assay results and cleaved caspase 3 and 12 were also determined. Ang(1-7) induced a reduction in SBP together with a restoration of RSNA in the rat model of CIH. Ang(1-7) treatment also suppressed the production of reactive oxygen species, reduced renal tissue inflammation, ameliorated mesangial expansion, and decreased renal fibrosis. Thus, Ang(1-7) treatment exerted renoprotective effects on CIH-induced renal injury and was associated with a reduction of oxidative stress, inflammation and fibrosis. Ang(1-7) might therefore represent a promising therapy for obstructive sleep apnea-related hypertension and renal injury.