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

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.

Obstructive sleep apnea and ambulatory blood pressure abnormalities in children with chronic kidney disease

BACKGROUND

Obstructive sleep apnea (OSA) and hypertension are common complications in children with chronic kidney disease (CKD). Progression of CKD can aggravate OSA and hypertension whereas worsening sleep apnea can make hypertension difficult to treat in CKD patients. We, therefore, conducted a prospective study to evaluate the association between OSA and hypertension in pediatric patients with CKD.

METHOD

In this prospective observational study consecutive children with CKD stage 3-5 (nondialysis dependent) underwent overnight polysomnography and 24-h ambulatory blood pressure monitoring (ABPM). The detailed clinical features and investigations were recorded in a prestructured performa.

RESULTS

Twenty-two children completed overnight polysomnography and 24-h ABPM was performed within 48 h of performing polysomnography. The median (IQR) age of the study population was 11 (8.5-15.5) years, with an age range of 5-18 years. Moderate-severe OSA defined as apnea-hypopnea index (AHI ≥5) was seen in 14 (63.6%) children, periodic limb movement syndrome in 20 (91%) and poor sleep efficacy in 9 (40.9%) children. Ambulatory blood pressure was abnormal in 15 (68.2%) children with CKD. Of them, 4 (18.2%) had ambulatory hypertension, 9 (40.9%) had severe ambulatory hypertension and 2 (9.1%) had masked hypertension. A statistically significant correlation of sleep efficiency with nighttime DBP SD score/Z score (SDS/Z) (r = -0.47; P = 0.02); estimated glomerular filtration rate with SBP loads (r = -0.61; P < 0.012); DBP loads (r = -0.63; P < ) and BMI with SBP load (r = 0.46; P = 0.012) was found.

CONCLUSION

Our preliminary findings suggest that ambulatory blood pressure abnormalities, OSA, periodic limb movement syndrome and poor sleep efficiency are highly prevalent in children with CKD stages 3-5.

Circadian rhythm and clinical characteristics in patients with acute myocardial infarction combined with obstructive sleep apnea

Objective

The present study aimed to investigate the circadian rhythm and clinical characteristics of patients with acute myocardial infarction (AMI) combined with obstructive sleep apnea (OSA).

Methods

Patients with AMI combined with OSA were enrolled in the study, and those that met the inclusion criteria were divided into three time‐period groups based on their sleep–wake rhythm (22:00–5:59, 6:00–13:59, and 14:00–21:59). The differences between the three groups of patients in sleep‐monitoring data, blood routine, biochemical indicators, and coronary angiographic parameters were analyzed and compared. Count data were expressed as the number of cases, and the chi‐square test was used for statistical analysis. Continuous data were expressed as mean ± standard deviation, and analysis of variance was used for the statistical analysis of these data. The characteristics of circadian rhythm and clinical features in patients with AMI combined with OSA were analyzed.

Results

Of the 148 patients, 90/148 (61%) had chest pain and 58/148 (39%) had non‐chest pain symptoms. In the 22:00–05:59 group, there were 70/148 (47%) patients with AMI (of these, 46/70 [66%] had chest pain). In the 06:00–13:59 period group, there were 44/148 (30%) patients with AMI (of these, 26/44 [60%] had chest pain). In the 14:00–21:59 period group, there were 34/148 (23%) patients with AMI (of these, 17/34 [50%] had chest pain). There was no statistically significant difference in the apnea–hypopnea index (AHI) and SYNTAX score between patients in the 22:00–5:59 and 6:00–13:59 groups. However, the AHI and SYNTAX scores in the 22:00–5:59 and 6:00–13:59 groups were higher than those in the 14:00–21:59 group, and the differences were statistically significant. In patients in the 22:00–5:59 group, the levels of serum D‐dimer (DD), hemoglobin (Hb), and oxygen desaturation index (ODI3) were higher, the sleep mean oxygen saturation (MeanSaO₂) was lower and the percentage of nighttime spent with oxygen saturation of less than 90% (Tsat₉₀) and less than 85% (Tsat₈₅) was longer.

Conclusion

The peak period for the onset of AMI in patients with OSA was 22:00–5:59, and the incidence of chest pain was high. During this period, patients had higher DD and Hb, higher ODI3, lower MeanSaO₂ during sleep, and longer TSat₉₀ and TSat₈₅. During the 22:00–5:59 and 6:00–13:59 periods, patients had higher AHI and a higher SYNTAX score.

New Approaches to Cardiovascular Disease and Its Management in Kidney Transplant Recipients

Cardiovascular events, including ischemic heart disease, heart failure, and arrhythmia, are common complications after kidney transplantation and continue to be leading causes of graft loss. Kidney transplant recipients have both traditional and transplant-specific risk factors for cardiovascular disease. In the general population, modification of cardiovascular risk factors is the best strategy to reduce cardiovascular events; however, studies evaluating the impact of risk modification strategies on cardiovascular outcomes among kidney transplant recipients are limited. Furthermore, there is only minimal guidance on appropriate cardiovascular screening and monitoring in this unique patient population. This review focuses on the limited scientific evidence that addresses cardiovascular events in kidney transplant recipients. Additionally, we focus on clinical management of specific cardiovascular entities that are more prevalent among kidney transplant recipients (ie, pulmonary hypertension, valvular diseases, diastolic dysfunction) and the use of newer evolving drug classes for treatment of heart failure within this cohort of patients. We note that there are no consensus documents describing optimal diagnostic, monitoring, or management strategies to reduce cardiovascular events after kidney transplantation; however, we outline quality initiatives and research recommendations for the assessment and management of cardiovascular-specific risk factors that could improve outcomes.

Correlation of Dyslipidemia and Inflammation With Obstructive Sleep Apnea Severity

Introduction: Obstructive sleep apnea (OSA) is a serious condition linked with various metabolic disorders and associated with increased all-cause and cardiovascular mortality. Although the potential mechanisms of pathophysiological processes related to OSA are relatively well known, the data regarding the correlation between obstructive sleep apnea, dyslipidemia, and systemic inflammation are still inconclusive.

Methods: The study was conducted as a retrospective cohort study including 328 patients with newly diagnosed obstructive sleep apnea during the period between April 2018, and May 2020, in University Clinical Hospital Center “Bezanijska kosa”, Belgrade, Serbia. Polysomnography was performed in all patients according to the protocol. Numerous demographic, antropometric, laboratory, and clinical data were correlated to Apnea-Hypopnea Index (AHI) as a dependent variable, with a particular review on the relation between lipid abnormalities, inflammatory parameters, and obstructive sleep apnea severity. Multivariate logistic regression model was used to assess predictors of severe OSA (AHI ≥30 per hour).

Results: A total of 328 patients were included in the study. The mean age of the patients was 54.0 ± 12.5 years and more than two-thirds were male (68.8%). The majority of the patients had an AHI of at least 30 events per hour. Patients with severe OSA were more frequently male, obese, hypertensive and hyperlipidemic, and had increased neck circumference (both male and female patients). One hundred and thirty-two patients had metabolic syndrome. Patients with severe OSA more frequently had metabolic syndrome and significantly higher levels of glucose, creatinine, uric acid, AST, ALT, CK, microalbumine/creatinine ratio, triglyceride, total cholesterol, HDL, total cholеsterol to HDL‐C ratio, CRP, and ESR. In the multivariate linear regression model with AHI (≥30 per hour) as a dependent variable, of demographic and clinical data, triglycerides ≥1.7 mmol/L and CRP >5 mg/L were significantly associated with AHI≥30 per hour.

Conclusion: The present study on 328 patients with newly diagnosed obstructive sleep apnea revealed significant relation of lipid abnormalities, inflammatory markers, and other clinically important data with obstructive sleep apnea severity. These results can lead to a better understanding of the underlying pathophysiological processes and open the door to a new world of potentially useful therapeutic modalities.

Role of the Nox4/AMPK/mTOR signaling axe in adipose inflammation-induced kidney injury

Diabetic kidney disease is one of the most serious complications of diabetes worldwide and is the leading cause of end-stage renal disease. While research has primarily focused on hyperglycemia as a key player in the pathophysiology of diabetic complications, recently, increasing evidence have underlined the role of adipose inflammation in modulating the development and/or progression of diabetic kidney disease. This review focuses on how adipose inflammation contribute to diabetic kidney disease. Furthermore, it discusses in detail the underlying mechanisms of adipose inflammation, including pro-inflammatory cytokines, oxidative stress, and AMPK/mTOR signaling pathway and critically describes their role in diabetic kidney disease. This in-depth understanding of adipose inflammation and its impact on diabetic kidney disease highlights the need for novel interventions in the treatment of diabetic complications.

Approach and Management of Hypertension After Kidney Transplantation

Hypertension is one of the most common cardiovascular co-morbidities after successful kidney transplantation. It commonly occurs in patients with other metabolic diseases, such as diabetes mellitus, hyperlipidemia, and obesity. The pathogenesis of post-transplant hypertension is complex and is a result of the interplay between immunological and non-immunological factors. Post-transplant hypertension can be divided into immediate, early, and late post-transplant periods. This classification can help clinicians determine the etiology and provide the appropriate management for these complex patients. Volume overload from intravenous fluid administration is common during the immediate post-transplant period and commonly contributes to hypertension seen early after transplantation. Immunosuppressive medications and donor kidneys are associated with post-transplant hypertension occurring at any time point after transplantation. Transplant renal artery stenosis (TRAS) and obstructive sleep apnea (OSA) are recognized but common and treatable causes of resistant hypertension post-transplantation. During late post-transplant period, chronic renal allograft dysfunction becomes an additional cause of hypertension. As these patients develop more substantial chronic kidney disease affecting their allografts, fibroblast growth factor 23 (FGF23) increases and is associated with increased cardiovascular and all-cause mortality in kidney transplant recipients. The exact relationship between increased FGF23 and post-transplant hypertension remains poorly understood. Blood pressure (BP) targets and management involve both non-pharmacologic and pharmacologic treatment and should be individualized. Until strong evidence in the kidney transplant population exists, a BP of <130/80 mmHg is a reasonable target. Similar to complete renal denervation in non-transplant patients, bilateral native nephrectomy is another treatment option for resistant post-transplant hypertension. Native renal denervation offers promising outcomes for controlling resistant hypertension with no significant procedure-related complications. This review addresses the epidemiology, pathogenesis, and specific etiologies of post-transplant hypertension including TRAS, calcineurin inhibitor effects, OSA, and failed native kidney. The cardiovascular and survival outcomes related to post-transplant hypertension and the utility of 24-h blood pressure monitoring will be briefly discussed. Antihypertensive medications and their mechanism of actions relevant to kidney transplantation will be highlighted. A summary of guidelines from different professional societies for BP targets and antihypertensive medications as well as non-pharmacological interventions, including bilateral native nephrectomy and native renal denervation, will be reviewed.

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.

Association of diagnosed obstructive sleep apnea with kidney transplant outcomes

Obstructive sleep apnea (OSA) is common but underdiagnosed among patients with kidney disease. This study examines whether the diagnosis of OSA in kidney transplant recipients (KTR) affected death, death-censored graft failure (DCGF), and acute rejection (AR). We analyzed the records of KTR who underwent transplant between 2000 and 2015. A total of 4014 kidney transplants were performed during the study period. Of these, 415 (10.3%) had a diagnosis of pretransplant OSA. Pretransplant OSA was associated with a higher risk of death in unadjusted analyses. After adjustment for potential confounders, pretransplant OSA was not associated with risk of death (HR = 1.04, 95% CI: 0.80-1.36). Similarly, pretransplant OSA was associated with a slightly higher incidence of DCGF or AR but neither associations were significant (HR: 1.23, 95% CI: 0.85-1.47 for DCGF; HR 1.10, 95% CI: 0.90-1.36 for AR). A total of 117 (3.3%) were diagnosed with de novo OSA after transplant. Similar to the pretransplant OSA, unadjusted HR for death was significantly higher in the de novo OSA group (HR: 1.48, 95% CI: 1.19-1.84); however, after adjustment, de novo OSA was not significantly associated with risk of death (HR: 1.15, 95% CI: 0.92-1.45). Similarly, DCGF and AR rates were not significantly associated with de novo OSA (HR: 1.10, 95% CI: 0.84-1.44 for DCGF; HR 1.10, 95% CI: 0.90-1.33 for AR). Our work did not detect significant associations between OSA and risk of death, graft failure, and rejection but the estimates might be underestimated due to underdiagnosis of OSA.

Cardiometabolic correlates of sleep-disordered breathing in renal transplant children

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

Independent Contributions of Obstructive Sleep Apnea and the Metabolic Syndrome to the Risk of Chronic Kidney Disease

STUDY OBJECTIVES

This retrospective study was conducted to evaluate the associations and interactions among obstructive sleep apnea (OSA), chronic kidney disease (CKD), and metabolic syndrome (MS).

METHODS

This study included 1,732 subjects (1,482 male and 250 female) in whom OSA was diagnosed by polysomnography. The severity of OSA was defined as mild, moderate, or severe with an apnea-hypopnea index (AHI) score of 5 to < 15, 15 to < 30, and ≥ 30 events/h, respectively. CKD was defined as an estimated glomerular filtration rate < 60 mL/min/1.73 m² or albuminuria.

RESULTS

The prevalence of MS was 29.2% (n = 505). One hundred twenty-nine subjects (7.4%) had CKD. In subjects with MS, CKD prevalence increased progressively with OSA severity: 7.4%, 12.5%, and 15.8% in those with mild, moderate, or severe OSA, respectively (P = .025). Each 10-point increment in AHI score was independently associated with a 1.15-fold higher prevalence of CKD [95% confidence interval (CI), 1.036-1.280; P = .009] after adjustment for all individual components of MS. On the contrary, in those without MS, AHI was not associated with increased odds for CKD [odds ratio, 1.054; 95% CI, 0.930-1.195].

CONCLUSIONS

The independent association between OSA severity and CKD prevalence was observed only in subjects with MS. Further studies are needed to ascertain if OSA contributes to the development of CKD in subjects with MS.

Insulin Resistance in Kidney Disease: Is There a Distinct Role Separate from That of Diabetes or Obesity?

Insulin resistance is a central component of the metabolic dysregulation observed in obesity, which puts one at risk for the development of type 2 diabetes and complications related to diabetes such as chronic kidney disease. Insulin resistance and compensatory hyperinsulinemia place one at risk for other risk factors such as dyslipidemia, hypertension, and proteinuria, e.g., development of kidney disease. Our traditional view of insulin actions focuses on insulin-sensitive tissues such as skeletal muscle, liver, adipose tissue, and the pancreas. However, insulin also has distinct actions in kidney tissue that regulate growth, hypertrophy, as well as microcirculatory and fibrotic pathways which, in turn, impact glomerular filtration, including that governed by tubuloglomerular feedback. However, it is often difficult to discern the distinct effects of excess circulating insulin and impaired insulin actions, as exist in the insulin resistance individual, from the associated effects of obesity or elevated systolic blood pressure on the development and progression of kidney disease over time. Therefore, we review the experimental and clinical evidence for the distinct impact of insulin resistance on kidney function and disease.