Obstructive sleep apnea syndrome and chronic kidney disease: a new cardiorenal risk factor

Association between obstructive sleep apnea and 24-h urine protein quantification in patients with hypertension

The association between obstructive sleep apnea (OSA) and proteinuria is undetermined, with few studies on hypertension, a high-risk group for renal impairment. Therefore, we aimed to explore whether OSA is an independent risk factor for proteinuria in patients with hypertension. We investigated the cross-sectional association between OSA and proteinuria. Participants were divided into groups by apnea hypopnea index (AHI) category. Multivariable Logistic regression analysis was used to evaluate the association between OSA severity, objectively measured sleep dimensions, and proteinuria which is mainly defined by 24-h urine protein quantification > 300 mg/24 h. Sensitivity analyses were performed by excluding those with comorbidities (primary aldosteronism and homocysteine ≥ 15 μmol/L). Of the 2106 participants, the mean age was 47.57 ± 10.50 years, 67.2% were men, and 75.9% were OSA patients. In total participants, compared with those without OSA, patients with mild OSA, moderate OSA, and severe OSA showed 1.09 (95% CI 0.80-1.40), 1.24 (95% CI 0.89-1.74) and 1.47 (95% CI 1.04-2.08) fold risk for proteinuria with a trend test P trend < 0.05. Each 10-unit increase in the AHI, oxygen desaturation index (ODI), and time spent with oxygen saturation < 90% (T90) was found to be associated with 13%, 10%, and 2% higher likelihood of proteinuria in the crude model, significant in adjusted models. The more severe the OSA is, the higher the risk of proteinuria. AHI and T90 are independently associated with a higher risk of structural renal damage in the population with hypertension.

Exploring Symptom Clusters in Chinese Patients with Diabetic Kidney Disease: A Network Analysis

Purpose

The research on symptom management in patients with diabetic kidney disease (DKD) has shifted from separate symptoms to symptom clusters and networks recently. This study aimed to evaluate the unpleasant symptoms of DKD patients, and to investigate how these symptom clusters could affect patients.

Methods

408 DKD patients were recruited in this cross-sectional study. The symptoms of DKD patients were measured using the modified Dialysis Symptom Index. Network analysis was employed to evaluate the symptom network and the characteristics of individual nodes, while factor analysis was utilized to identify symptom clusters.

Results

Blurred vision was the most prevalent symptom among DKD patients. The symptoms identified as the most distressing, severe, and frequent were light headache or dizziness, arteriovenous fistula/catheterization pain, and diarrhea, respectively. Five symptom clusters were obtained from factor analysis, and the most central symptom cluster in the entire symptom network was sexual dysfunction.

Conclusion

This study identified five symptom clusters in Chinese DKD patients, with sexual dysfunction emerging as the most central cluster. These findings carry significant clinical implications, underscoring the necessity of assessing symptom clusters and their associations to enhance symptom management in DKD patients. Further research is essential to elucidate the underlying mechanisms of symptoms and to clarify the associations among symptoms in DKD patients across different disease trajectories or treatment modalities.

Continuous Positive Airway Pressure Effect on Progression of Retinal Disease in Patients with Sleep Apnea and Nonproliferative Diabetic Retinopathy: A Randomized Clinical Trial

Rationale: Obstructive sleep apnea (OSA) is associated with impaired glycemic control and a higher risk of vascular complications, such as diabetic retinopathy. However, the effect of apnea-hypopnea suppression on retinal disease progression is unclear. Objectives: To evaluate the efficacy and safety of continuous positive airway pressure (CPAP) for the reduction of retinal lesions in patients with non-proliferative diabetic retinopathy (NPDR) and OSA. Methods: This open-label, parallel-group, randomized controlled trial was conducted between October 2016 and February 2020 at a university hospital in Spain. The date of final follow-up was March 2, 2021. Eighty-three patients with OSA and mild to moderate NPDR receiving stable treatment were randomized to receive CPAP and usual care (43 patients with 79 available eyes) or usual care alone (40 patients with 67 available eyes) for 52 weeks. The primary outcomes were the change in the percentage of eyes with retinal exudates and the number of retinal microhemorrhages from baseline to week 52. We also assessed the effects of both interventions on retinal thickness by means of optical coherence tomography, serum concentrations of glycated hemoglobin, blood pressure, lipid concentrations, sleepiness, and quality of life. Results: Fifty-two weeks of CPAP treatment was associated with reductions from baseline in the percentage of eyes with hard exudates (overall difference, -21.7%; P = 0.035) and in optical coherence tomography indices of retinal edema, including central subfield thickness and cube volume. However, in patients who met prespecified criteria for CPAP adherence, treatment was also associated with a higher number of retinal microhemorrhages at 52 weeks (intergroup adjusted difference, 6.0 [95% confidence interval, 0.6-11.5]; P = 0.029), which was directly related to prescribed pressure levels. CPAP treatment also improved glycemic control, sleepiness, and general health-related quality of life. Conclusions: In patients with OSA and NPDR, long-term CPAP treatment in addition to usual care may result in slower progression of retinal disease, although it could also induce an increase in retinal microhemorrhages. Clinical trial registered with www.clinicaltrials.gov (NCT02874313).

The relationship between obstructive sleep apnea and risk of renal impairment in patients with hypertension, a longitudinal study

OBJECTIVE

Association of obstructive sleep apnea (OSA) with renal damage is undetermined, especially in the population with hypertension, a high-risk group for chronic kidney disease. Therefore, we aimed to explore whether OSA is an independent risk factor for renal impairment in patients with hypertension, by considering the effects of gender, age, obesity and OSA severity.

METHODS

The longitudinal observational study included patients with hypertension and suspected OSA without renal damage at baseline who visited Hypertension Center between January 2011 and December 2018, and followed up till renal outcomes, death, loss to follow-up, or May 31, 2022, using annual health check-ups, hospital readmission or out-patient visits. Main renal outcome was chronic kidney disease (CKD), defined as estimated glomerular filtration rate <60 ml/min per 1.73 m2 and/or positive proteinuria. Cox proportional hazard models were used to evaluate the association, and repeated after propensity score matching. Sensitivity analysis were performed by excluding those with primary aldosteronism.

RESULTS

7961 patients with hypertension were included with 5022 ones with OSA, and 82% were followed up. During median follow-up of 3.42 years, 1486 patients developed CKD. Per 1000 person-year incidence of CKD was 56.72 in OSA group. In Cox regression analysis, OSA and severe OSA group respectively showed 1.21 (95% CI: 1.08-1.35) and 1.27 (95% CI: 1.09-1.47) fold risk for CKD in total, compared with non-OSA group. Overall results remained consistent in propensity score matching and sensitivity analysis.

CONCLUSION

OSA is independently associated with higher risk of chronic kidney disease in hypertension.

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.

Continuous Positive Airway Pressure Effect on Albuminuria Progression in Patients with Obstructive Sleep Apnea and Diabetic Kidney Disease: A Randomized Clinical Trial

Rationale: Obstructive sleep apnea (OSA) is associated with impaired glycemic control and a higher risk of vascular complications, such as diabetic kidney disease (DKD). However, the effect of apnea-hypopnea suppression on DKD progression is unclear. Objectives: To assess the effect of continuous positive airway pressure (CPAP) on the urinary albumin-to-creatinine ratio (UACR) in patients with DKD and OSA. Methods: In a 52-week, multicentric, open-label, parallel, and randomized clinical trial, 185 patients with OSA and DKD were randomized to CPAP and usual care (n = 93) or usual care alone (n = 92). Measurements and Main Results: UACR, estimated glomerular filtration rate, serum concentrations of creatinine and glycated hemoglobin, insulin resistance, lipid concentrations, sleepiness, and quality of life. A 52-week change in UACR from baseline did not differ significantly between the CPAP group and the usual-care group. However, in per-protocol analyses that included 125 participants who met prespecified criteria for adherence, CPAP treatment was associated with a great reduction in UACR (mean difference, -10.56% [95% confidence interval, -19.06 to -2.06]; P = 0.015). CPAP effect on UACR was higher in nonsleepy patients with more severe OSA, worse renal function, and a more recent diagnosis of DKD. CPAP treatment also improved glycemic control and insulin resistance, as well as sleepiness and health-related quality of life. Conclusions: In patients with OSA and DKD, the prescription of CPAP did not result in a statistically significant reduction in albuminuria. However, good adherence to CPAP treatment in addition to usual care may result in long-term albuminuria reduction compared with usual care alone. Clinical trial registered with www.clinicaltrials.gov (NCT02816762).

Potential Use of SGLT-2 Inhibitors in Obstructive Sleep Apnea: A new treatment on the horizon

BACKGROUND

Obstructive sleep apnea (OSA) is characterized by hypoxic episodes due to collapse of the airway during sleep and is frequently associated with obesity, type 2 diabetes mellitus (T2DM) and cardiovascular diseases (CVD). There is currently no pharmacological agent approved for the treatment of OSA. Sodium-glucose cotransporter-2 (SGLT2) inhibitors have the potential to both increase life expectancy and quality of life of these patients making them promising agents for this role. There are relatively few studies investigating this possible beneficial relationship between these drugs and OSA.

METHOD

We aimed to increase awareness on the potential benefits of SGLT2 inhibitors in OSA patients by describing the current evidence on the effectiveness of these inhibitors in both overall and cardiovascular morbidity and mortality. We performed a literature search for articles reporting on the use of SGLT2 inhibitors in patients with OSA and T2DM.

RESULTS

We identified 4 manuscripts studying the use of SGLT2 inhibitors in 475 OSA patients with T2DM. Among them, 332 patients were administered SGLT2 inhibitors, and 143 patients were in a control group. SGLT2 inhibitors have many potential positive impacts on OSA patients by targeting various mechanisms involved in OSA pathogenesis.

CONCLUSION

SGLT2 inhibitors are prime pharmacological candidates for the treatment of OSA, and additional studies are needed to better explore mechanisms and outcomes unique to this population. Additionally, patients with OSA often have multiple comorbidities that are clinical indications for SGLT2 inhibitor therapy. Physicians should recognize and encourage the use of these agents in such patients.

Lung Dysfunction and Chronic Kidney Disease: A Complex Network of Multiple Interactions

Chronic kidney disease (CKD) is a progressive disease that affects > 10% of the total population worldwide or >800 million people. CKD poses a particularly heavy burden in low- and middle-income countries, which are least able to cope with its consequences. It has become one of the leading causes of death worldwide and is one of the few non-communicable diseases where the number of related deaths has increased over the last two decades. The high number of people affected, and the significant negative impact of CKD should be a reason to increase efforts to improve prevention and treatment. The interaction of lung and kidney leads to highly complex and difficult clinical scenarios. CKD significantly affects the physiology of the lung by altering fluid homeostasis, acid-base balance and vascular tone. In the lung, haemodynamic disturbances lead to the development of alterations in ventilatory control, pulmonary congestion, capillary stress failure and pulmonary vascular disease. In the kidney, haemodynamic disturbances lead to sodium and water retention and the deterioration of renal function. In this article, we would like to draw attention to the importance of harmonising the definitions of clinical events in pneumology and renal medicine. We would also like to highlight the need for pulmonary function tests in routine clinical practise for the management of patients with CKD, in order to find new concepts for pathophysiological based disease-specific management strategies.

Assessment of hypertension in obstructive sleep apnea by ambulatory blood pressure monitoring: a systematic review and meta-analysis

Among obstructive sleep apnea (OSA) patients, there exists a high prevalence of hypertension. Determining the optimal blood pressure (BP) monitoring modality in this population will lead to a better understanding of hypertension profiles and a more accurate diagnosis of hypertension. PubMed, Ovid/Medline, Web of Science, Scopus, Cochrane Library, and CINAHL databases were screened, and the relevant articles regarding BP monitoring in OSA patient population were selected. Studies evaluating both ambulatory (ABPM) and office BP measurements were selected to be analyzed for the hypertension diagnosis specificity of ABPM measurement in OSA patients compared with office measurements. If reported, additional information regarding white-coat, masked hypertension, and circadian BP pattern prevalence was included. A cumulative analysis of five studies revealed a prevalence of hypertension based on BP to be 44%, whereas a cumulative analysis of four studies revealed a prevalence of hypertension based on ABPM to be 66%. Excluding a study with the nighttime assessment of hypertension reduced the cumulative prevalence of hypertension in OSA patients to 59%. The cumulative prevalence of Studies demonstrated the prevalence of masked and white-coat hypertension to be 34 and 9%, respectively. As a higher prevalence of hypertension was detected by ABPM and nighttime measurement, it can be deduced that ABPM is more sensitive in determining OSA patients with hypertension, and that nighttime ABPM further increases this sensitivity. The presence of masked and white-coat hypertension in OSA patients underlines the importance of correct hypertension diagnosis as it affects further management in this population with increased cardiovascular risk.

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.

Does obstructive sleep apnoea contribute to obesity, hypertension and kidney dysfunction in children? A systematic review protocol

INTRODUCTION

Childhood obstructive sleep apnoea (OSA) is a highly prevalent disorder that may directly contribute to the development of obesity, hypertension and renal injury. Although those associations seem to be clearer in adults, studies in children have revealed conflicting results and updated synthesis of the evidence is lacking. The aim of this systematic review is to summarise the available evidence on the effect of OSA on obesity, systemic blood pressure and kidney function, to help to elucidate whether respiratory interventions to correct OSA would have the potential to improve those outcomes.

METHODS AND ANALYSIS

A systematic literature review search was created by a medical librarian and peer-reviewed by a second librarian prior to running. Ovid Medline, Ovid Embase, CINAHL via EbscoHOST, Wiley Cochrane Library and ProQuest Dissertations and Theses Global were searched on 25 February 2020. Titles and abstracts will be screened by two independent reviewers for inclusion, followed by full-text screening of relevant articles. Studies in children will be included if they report data on OSA and weight, systemic blood pressure or kidney parameters. The extracted data will be combined for analysis and the information subcategorised in groups based on outcome. Risk of bias will be determined using tools specific to study methodology and certainty of the evidence using the Grading of Recommendations, Assessment, Development and Evaluations approach.

ETHICS AND DISSEMINATION

This study will provide essential information for healthcare professionals to better understand the relationship between childhood OSA and changes in body mass index, systemic blood pressure and kidney function indicators. Our findings will be disseminated through conferences and publications. The results of this review may guide the initiation of new strategies and the development of future research studies. This research did not involve human subjects and therefore did not undergo research ethical review.

PROSPERO REGISTRATION NUMBER

CRD42020171186.

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.

Is Aberrant Reno-Renal Reflex Control of Blood Pressure a Contributor to Chronic Intermittent Hypoxia-Induced Hypertension?

Renal sensory nerves are important in the regulation of body fluid and electrolyte homeostasis, and blood pressure. Activation of renal mechanoreceptor afferents triggers a negative feedback reno-renal reflex that leads to the inhibition of sympathetic nervous outflow. Conversely, activation of renal chemoreceptor afferents elicits reflex sympathoexcitation. Dysregulation of reno-renal reflexes by suppression of the inhibitory reflex and/or activation of the excitatory reflex impairs blood pressure control, predisposing to hypertension. Obstructive sleep apnoea syndrome (OSAS) is causally related to hypertension. Renal denervation in patients with OSAS or in experimental models of chronic intermittent hypoxia (CIH), a cardinal feature of OSAS due to recurrent apnoeas (pauses in breathing), results in a decrease in circulating norepinephrine levels and attenuation of hypertension. The mechanism of the beneficial effect of renal denervation on blood pressure control in models of CIH and OSAS is not fully understood, since renal denervation interrupts renal afferent signaling to the brain and sympathetic efferent signals to the kidneys. Herein, we consider the currently proposed mechanisms involved in the development of hypertension in CIH disease models with a focus on oxidative and inflammatory mediators in the kidneys and their potential influence on renal afferent control of blood pressure, with wider consideration of the evidence available from a variety of hypertension models. We draw focus to the potential contribution of aberrant renal afferent signaling in the development, maintenance and progression of high blood pressure, which may have relevance to CIH-induced hypertension.

Self-reported snoring is associated with chronic kidney disease independent of metabolic syndrome in middle-aged and elderly Chinese

AIMS/INTRODUCTION

To investigate the correlation between snoring and chronic kidney disease (CKD), and explore whether metabolic syndrome (MetS) plays an important role in this relationship among middle-aged and elderly Chinese.

MATERIALS AND METHODS

The participants included in the present study were categorized into three subgroups based on self-reported snoring frequency (regularly [≥3 times per week], occasionally [between 'regularly' and 'never'] or never [<1 time per month]). An estimated glomerular filtration rate <60 mL/min/1.73 m2 was considered as CKD. We diagnosed MetS based on the 2004 Chinese Diabetes Society criteria. We explored the relationship between snoring and CKD by using multiple logistic regressions.

RESULTS

The frequency of MetS, MetS components and CKD was dramatically higher in regular snorers than in non-snorers and occasional snorers. The odds ratios for MetS and all the MetS elements, except for hyperglycemia, increased progressively with the snoring frequency (P < 0.001). Upon additional adjustment for other MetS components, snoring was not significantly related with hypertension; however, the associations between snoring frequency and overweight/obesity and dyslipidemia became attenuated, but still remained statistically significant (P < 0.01). Interestingly, odds ratios for CKD also increasingly augmented with snoring frequency (P < 0.001). Upon further adjustment for individual MetS components or MetS, regular snoring also resulted in a significantly increased odds ratio for CKD (odds ratio 1.72; P = 0.034) relative to non-snoring.

CONCLUSIONS

Self-reported snoring is closely associated with CKD independent of MetS among middle-aged and elderly Chinese.

Intermittent hypoxia exacerbates increased blood pressure in rats with chronic kidney disease

Kidney injury and sleep apnea (SA) are independent risk factors for hypertension. Exposing rats to intermittent hypoxia (IH) to simulate SA increases blood pressure whereas adenine feeding causes persistent kidney damage to model chronic kidney disease (CKD). We hypothesized that exposing CKD rats to IH would exacerbate the development of hypertension and renal failure. Male Sprague-Dawley rats were fed a 0.2% adenine diet or control diet (Control) until blood urea nitrogen was >120 mg/dl in adenine-fed rats (14 ± 4 days, mean ± SE). After 2 wk of recovery on normal chow, rats were exposed to IH (20 exposures/h of 5% O₂-5% CO₂ 7 h/day) or control conditions (Air) for 6 wk. Mean arterial pressure (MAP) was monitored with telemeters, and plasma and urine samples were collected weekly to calculate creatinine clearance as an index of glomerular filtration rate (GFR). Prior to IH, adenine-fed rats had higher blood pressure than rats on control diet. IH treatment increased MAP in both groups, and after 6 wk, MAP levels in the CKD/IH rats were greater than those in the CKD/Air and Control/IH rats. MAP levels in the Control/Air rats were lower than those in the other three groups. Kidney histology revealed crystalline deposits, tubule dilation, and interstitial fibrosis in both CKD groups. IH caused no additional kidney damage. Plasma creatinine was similarly increased in both CKD groups throughout whereas IH alone increased plasma creatinine. IH increases blood pressure further in CKD rats without augmenting declines in GFR but appears to impair GFR in healthy rats. We speculate that treating SA might decrease hypertension development in CKD patients and protect renal function in SA patients.

Sleep duration and chronic kidney disease: The Korean Genome and Epidemiology Study (KoGES)-Kangwha study

BACKGROUND/AIMS

Sleep duration affects health in various ways. The objective of this study was to investigate the associations of sleep duration with chronic kidney disease (CKD) in a Korean adult population.

METHODS

This cross-sectional analysis was conducted for total of 1,360 participants who completed baseline health examinations for the Korean Genome and Epidemiology Study-Kangwha study in 2010 to 2011. Sleep habits were measured by an interviewer-assisted questionnaire. Sleep duration was calculated based on the number of hours per day participants had slept over the past 1 year. CKD was defined as either proteinuria or estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m². Multiple logistic regression models were applied to examine associations between sleep duration and CKD.

RESULTS

Women with very long sleep duration (≥ 9 hours/day) were at significantly increased odds for having high serum creatinine (odds ratio [OR], 2.936; 95% confidence interval [CI], 1.176 to 7.326), low eGFR (OR, 3.320; 95% CI, 1.372 to 8.034), and CKD (OR, 3.112; 95% CI, 1.315 to 7.363), compared those with a typical sleep duration (7 to < 8 hours/day), after adjusting for sociodemographic status, socioeconomic status, health behaviors, comorbidities, and sleep quality. Among women, for every 1 hour increase in sleep duration per day, there was a 24.6% increase in the presence of CKD (OR, 1.246; 95% CI, 1.019 to 1.523). However, among men, sleep duration was not significantly associated with CKD.

CONCLUSIONS

Very long sleep duration was independently associated with a higher prevalence of CKD among Korean women. Gender may influence this association.

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.

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

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

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.

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.

Pharmacological models and approaches for pathophysiological conditions associated with hypoxia and oxidative stress

Hypoxia is the failure of oxygenation at the tissue level, where the reduced oxygen delivered is not enough to satisfy tissue demands. Metabolic depression is the physiological adaptation associated with reduced oxygen consumption, which evidently does not cause any harm to organs that are exposed to acute and short hypoxic insults. Oxidative stress (OS) refers to the imbalance between the generation of reactive oxygen species (ROS) and the ability of endogenous antioxidant systems to scavenge ROS, where ROS overwhelms the antioxidant capacity. Oxidative stress plays a crucial role in the pathogenesis of diseases related to hypoxia during intrauterine development and postnatal life. Thus, excessive ROS are implicated in the irreversible damage to cell membranes, DNA, and other cellular structures by oxidizing lipids, proteins, and nucleic acids. Here, we describe several pathophysiological conditions and in vivo and ex vivo models developed for the study of hypoxic and oxidative stress injury. We reviewed existing literature on the responses to hypoxia and oxidative stress of the cardiovascular, renal, reproductive, and central nervous systems, and discussed paradigms of chronic and intermittent hypobaric hypoxia. This systematic review is a critical analysis of the advantages in the application of some experimental strategies and their contributions leading to novel pharmacological therapies.

Renoprotective effects of continuous positive airway pressure in chronic kidney disease patients with sleep apnea

PURPOSE

Chronic kidney disease (CKD) is associated with a high incidence of obstructive sleep apnea (OSA). We assessed the effect of continuous positive airway pressure (CPAP) on renal function in patients with CKD and OSA.

METHODS

In this retrospective cohort study, 42 patients with Stage 3-5 CKD and OSA were stratified into two groups: patients who use CPAP more (average >4 h/night on >70 % of nights) and patients who use CPAP less (average ≤4 h/night on ≤70 % of nights). Median follow-up time was 2.3 (1.6-2.9) years for greater and 2.0 (0.6-3.5) years for lesser CPAP users. Chart reviews were carried out to record clinical characteristics, proteinuria measurements by urine dipstick, and eGFR values calculated by CKD-EPI equations. Univariate analyses were performed using Wilcoxon rank-sum and Kruskal-Wallis tests. Multivariate logistic regression models were applied to assess eGFR decline after CPAP prescription.

RESULTS

Twelve (29 %) of the 42 subjects used CPAP more. Groups were similar with respect to age, body mass index, blood pressure, Charlson Comorbidity Index, and baseline eGFR and proteinuria. The median rate of decline of eGFR was significantly slower at -0.07 mL/min/1.73 m(2)/year (range -30 to 13) in those who used more CPAP compared to those who used it less at -3.15 mL/min/1.73 m(2)/year (range -27 to 7) (p = 0.027).Greater use of CPAP was also associated with a significantly reduced level of proteinuria at 0.15 (range 0.0-3.0) versus 0.70 g/L (range 0.0-3.0) (p = 0.046). Less compliant CPAP users were more likely to have progressive decline of eGFR (decline >3 mL/min/1.73 m(2)/year), with unadjusted OR 5.0 (95 % CI 0.93-26.8) and adjusted OR 8.9 (95 % CI 1.1-72.8), adjusting for CCI and baseline eGFR.

CONCLUSIONS

Compliance to CPAP therapy is associated with a slower rate of progression of CKD in patients with CKD and OSA.

Tailoring therapy to improve the treatment of children with obstructive sleep apnea according to grade of adenotonsillar hypertrophy

BACKGROUND

Obstructive sleep apnea (OSA) is a common disease in children with the major causes of hypertrophy of adenoid or tonsil and nasal diseases. The treatment methods for this disease include the resection of adenoid or tonsil, and drug therapy as well. However, no agreement on the selection of treatment method is available to date.

OBJECTIVE

To investigate the individualized treatment methods for children with OSA with different sizes of adenoids and tonsils.

METHODS

Children with OSA (diagnosed by polysomnography) were included into groups A (adenoid/tonsil grade ≤III) and B (adenoid/tonsil grade=IV), and further subdivided into subgroups A1 (3-month medication), A2 (3-month medication and negative-pressure sputum aspiration [NPSA]), B1 (3-month medication plus NPSA), B2 (coblation adenotonsillectomy with preoperative/postoperative medication for 3 days/2 weeks) and B3 (coblation adenotonsillectomy with preoperative/postoperative medication for 2 weeks/3 months). Six-month outcomes included quality of life for children with obstructive sleep apnea-18 item (OSA-18), obstructive apnea index (OAI), apnea hypopnea index (AHI) and lowest oxygen saturation (LSaO2).

RESULTS

Three hundred and eighty six patients (310 male; 6.70±2.44 years-old) were included. Preoperative OSA-18, OAI, AHI and LSaO2 were not significantly different. At all postoperative time points, subgroup A2 had significantly lower OSA-18 than subgroup A1; postoperative improvements in OAI, AHI and LSaO2 were also superior in subgroup A2 (P<0.05). The initial decrease in OSA-18 was not maintained in subgroups B1 and B2, whereas subgroup B3 showed a sustained reduction at 6 months. OAI and AHI were more improved in subgroup B3 (P<0.05). Surgical/anesthetic complications in subgroups B2 and B3 were 5.5% and 0%.

CONCLUSION

Conservative therapy could achieve satisfactory outcomes in children with grade III hypertrophy, while surgery and drugs could achieve good outcomes in grade IV.

Uric acid as a potential mediator of cardiovascular morbidity in obstructive sleep apnea syndrome

BACKGROUND AND AIMS

Obstructive sleep apnea (OSA) is now considered as an independent risk factor for cardiovascular (CV) disease. Although uric acid is increasingly being implicated in CV morbidity and mortality, no study attempted to determine independent role of uric acid in CV morbidity of OSA patients. We aimed to assess the role of serum uric acid as a potential mechanism of CV morbidity in a nonselected cohort of OSA patients.

METHODS

This was a cohort study in which patients who had undergone a formal sleep study for diagnosis of OSA were recruited. Included patients were grouped according to apnea-hypopnea index (AHI) as mild, moderate and severe OSA. Patients with AHI<5 served as control group. Patients were interrogated as to cardiovascular morbid conditions which included prior history and an established diagnosis of coronary artery disease, cerebrovascular accident, congestive heart failure due to coronary artery disease and arrhythmias.

RESULTS

436 OSA patients included (72 controls, 97 with mild, 75 with moderate, and 192 with severe OSA). The severe group also had higher serum uric acid level compared with the control and other OSA groups. Linear regression showed that the Ln uric acid was positively associated with Ln AHI score. In unadjusted logistic regression, severe OSA was associated with higher odds of a cardiovascular event, OR=2.81 (1.307-6.041), p=0.0081 while the other categories of sleep apnea were not. However, severe OSA was no longer significant after adjusting for age, gender, diabetes mellitus status, hypertension status, BMI, and smoking, OR=1.882 (0.826-4.287), p=0.1322. Uric acid was significantly higher in those who had a cardiovascular event even in the mild, moderate and severe OSA groups.

CONCLUSION

Hyperuricemia is strongly associated with cardiovascular disease in OSA patients. This strong relationship persists even after controlling for well-known traditional risk factors for cardiovascular disease.