Sleep Apnea and Hypertension: Prevalence in Chronic Kidney Disease

Is kidney a new organ target in patients with obstructive sleep apnea? Research priorities in a rapidly evolving field

The bidirectional relationship between sleep disordered breathing and chronic kidney disease (CKD) has recently gained a lot of interest. Several lines of evidence suggest the high prevalence of coexistent obstructive sleep apnea (OSA) in patients with CKD and end-stage renal disease (ESRD). In addition, OSA seems to result in loss of kidney function in some patients, especially in those with cardio-metabolic comorbidities. Treatment of CKD/ESRD and OSA can alter the natural history of each other; still better phenotyping with selection of appropriate treatment approaches is urgently needed. The aim of this narrative review is to provide an update of recent studies on epidemiological associations, pathophysiological interactions, and management of patients with OSA and CKD or ESRD.

Comparisons of sleep apnoea rate and outcomes among patients with resistant and non-resistant hypertension

BACKGROUND AND OBJECTIVE

We directly compared sleep apnoea (SA) rates and risk of cardiovascular and mortality outcomes among SA patients with resistant hypertension (RH) and non-RH within a large diverse hypertension population.

METHODS

A retrospective cohort study between 1 January 2006 and 31 December 2010 among hypertensive adults (age ≥ 18 years) was performed within an integrated health system. Rates of SA in RH and non-RH were determined. Multivariable logistic regression analyses were used to calculate OR for SA. Cox proportional hazard modelling was used to estimate hazard ratios (HRs) for cardiovascular and mortality outcomes between SA in RH versus SA in non-RH adjusting for age, gender, race, BMI, chronic kidney disease and other comorbidities.

RESULTS

SA was identified in 33 682 (7.2%) from 470 386 hypertensive individuals. SA in RH accounted for 5806 (9.6%) compared to SA in non-RH 27 876 individuals (6.8%). Multivariable OR (95% CI) for SA was 1.16 (1.12, 1.19), 3.57 (3.47, 3.66) and 2.20 (2.15, 2.25) for RH versus non-RH, BMI ≥ 30, and males, respectively. Compared to SA in non-RH individuals, SA in RH had a multivariable adjusted HR (95% CI) of 1.24 (1.13, 1.36), 1.43 (1.28, 1.61), 0.98 (0.85, 1.12) and 1.04 (0.95, 1.14) for ischaemic heart event (IHE), congestive heart failure (CHF), stroke and mortality, respectively.

CONCLUSION

We observed a modest increase in likelihood for SA among RH compared to non-RH patients. Risks for IHE and CHF were higher for SA in RH compared to SA in non-RH patients; however, there were no differences in risk for stroke and mortality.

Treatment Strategies to Prevent Renal Damage in Hypertensive Children

Hypertension secondary to chronic kidney disease prevails in earlier childhood and obesity-related primary hypertension in adolescence. Both are associated with a high risk of renal and cardiovascular morbidity. In children with chronic kidney disease, uncontrolled hypertension may accelerate progression to end-stage renal disease before adulthood is reached and increase a child’s risk of cardiac death a thousand-fold. Obesity-related hypertension is a slow and silent killer, and though early markers of renal damage are recognized during childhood, end-stage renal disease is a risk in later life. Renal damage will be a formidable multiplier of cardiovascular risk for adults in whom obesity and hypertension tracks from childhood. Management options to prevent renal damage will vary for these different target groups. This review provides a summary of the available renoprotective strategies in order to aid physicians involved in the care of this challenging group of children.

Pharmacologic treatment of hypertension in patients with chronic kidney disease

Hypertension remains an important cause of morbidity and mortality in patients with chronic kidney disease. It both contributes to and is a consequence of chronic renal dysfunction. There is a high prevalence of hypertension in chronic kidney disease, and rates of control remain sub-optimal. Numerous studies have highlighted the benefit of treating hypertension in reducing the overall mortality as well as progression of renal disease in this population. Non-pharmacologic treatment strategies remain the primary intervention in all patients but are insufficient on their own to control hypertension in most cases. Pharmacologic treatment recommendations, however, vary depending on the specific etiology of disease as well as patient characteristics. Though most classes of anti-hypertensive drugs can be used to lower blood pressure in chronic kidney disease, therapy needs to be selected based on the presence of specific co-morbidities as well as the etiology of the kidney disease. Most patients will require multi-drug therapy for achieving target blood pressure goals. This review discusses the pharmacologic options in management of hypertension in various forms of chronic kidney disease.

Sleep apnea in early childhood associated with preterm birth but not small for gestational age: a population-based record linkage study

STUDY OBJECTIVES

Investigate the relationship between gestational age and weight for gestational age and sleep apnea diagnosis in a cohort of children aged up to 6 years old.

DESIGN

A cohort study, using record linked population health data.

SETTING

New South Wales, Australia.

PARTICIPANTS

398,961 children, born between 2000 and 2004, aged 2.5 to 6 years.

MEASUREMENTS

The primary outcome was sleep apnea diagnosis in childhood, first diagnosed between 1 and 6 years of age. Children with sleep apnea were identified from hospital records with the ICD-10 code G47.3: sleep apnea, central or obstructive.

RESULTS

A total of 4,145 (1.0%) children with a first diagnosis of sleep apnea were identified. Mean age at first diagnosis was 44.2 months (SD 13.9). Adenoidectomy, tonsillectomy, or both were common among the children diagnosed with sleep apnea (85.6%). Children born preterm compared to term were significantly more likely to be diagnosed with sleep apnea (< 32 weeks versus term hazard ratio 2.74 [95% CI: 2.16, 3.49]) this remained even after adjustment for known confounding variables. Children born small for gestational age were not at increased risk of sleep apnea compared to children born appropriate for gestational age, hazard ratio 0.95 (95% CI 0.86-1.06).

CONCLUSIONS

This is the largest study investigating preterm birth and sleep apnea diagnosis and suggests that diagnosis of sleep disordered breathing is more prevalent in children born preterm, but not those who are small for gestational age.

Improving prognosis estimation in patients with heart failure and the cardiorenal syndrome

The coexistence of heart failure and renal dysfunction constitutes the “cardiorenal syndrome” which is increasingly recognized as a marker of poor prognosis. Patients with cardiorenal dysfunction constitute a large and heterogeneous group where individuals can have markedly different outcomes and disease courses. Thus, the determination of prognosis in this high risk group of patients may pose challenges for clinicians and for researchers alike. In this paper, we discuss the cardiorenal syndrome as it pertains to the patient with heart failure and considerations for further refining prognosis and outcomes in patients with heart failure and renal dysfunction. Conventional assessments of left ventricular function, renal clearance, and functional status can be complemented with identification of coexistent comorbidities, medication needs, microalbuminuria, anemia, biomarker levels, and pulmonary pressures to derive additional prognostic data that can aid management and provide future research directions for this challenging patient group.

Review article: Managing sleep apnoea in kidney diseases

A higher prevalence of sleep apnoea (SA) has been observed in the chronic kidney disease (CKD) population compared with estimates in the general population. Increased rates of SA have been described in patients with various renal-related diagnoses including dialysis, renal transplant, early-stage CKD and proteinuria. The mechanism or underlying aetiology for this association is different for each type of kidney disease. The extracellular fluid volume and metabolic derangements that characterize the uremic state likely contributes to SA in the dialysis population. SA causing direct renal insults from haemodynamic changes, ischaemic stress, or an intermediary condition such as hypertension, can lead to early CKD and proteinuria. While renal transplantation has cured SA in some patients, the post-transplant state is itself a risk factor for SA. The high prevalence of SA in kidney disease and the associated clinical implications warrant vigilance in diagnosis and treatment of SA in the CKD patient. This review focuses on the prevalence of SA in patients with CKD including dialysis and transplant patients, and those with early-stage CKD and proteinuria. SA may vary in form and aetiology depending on type or stage of CKD. Based on these associations, we discuss our rationale for recommendations on screening and management of SA specific to the CKD population.