Sleep apnea is not associated with worse outcomes in kidney transplant recipients

Sleep Disorders in CKD: A Review

Sleep disorders are highly prevalent in patients with chronic kidney disease (CKD) but are often underrecognized. The most common sleep disturbances in people with CKD include insomnia, sleep apnea syndrome, restless legs syndrome, and periodic limb movement disorder. The presence of sleep disorders in CKD can further worsen the burden of high morbidity and mortality in a patient population with already high mortality rates. The detection and management of sleep disorders in patients with CKD are often challenging because the classic symptoms of sleep disorders (poor concentration, daytime sleepiness, and insomnia) overlap with CKD symptomatology. The treatment of one symptom may have a negative impact on others; hence treatment of these disorders is challenging and may need to be individualized and modified based on the response to treatment and the development of adverse effects. However, treatment of sleep disorders may have significant clinical benefits, leading to improved health-related quality of life. This Review presents an overview of sleep disorders in patients with CKD, with emphasis on relevant pathophysiology, diagnosis and treatment strategies.

Sleep-Related Disorders in Patients with CKD and Kidney Transplant Recipients

Sleep disorders such as insomnia, restless legs syndrome (RLS), and sleep apnea (SA) are common in patients with CKD. These conditions tend to become more prevalent and more severe as kidney function deteriorates and when a patient reaches ESKD. The prevalence of insomnia in the general population ranges from 4% to 29% compared with ( 1 ) 30%-67%, ( 2 ) 39%-54%, ( 3 ) 41%-79%, and ( 4 ) 9%-49% in patients with CKD, on hemodialysis, on peritoneal dialysis (PD), or in kidney transplant recipients (KTRs), respectively. RLS occurs in approximately 1%-15% of the general population compared with ( 1 ) 5%-18%, ( 2 ) 24%-33%, ( 3 ) 23%-64%, and ( 4 ) 6%-8% in patients with CKD, on hemodialysis, on PD, or in KTRs, respectively. Obstructive SA has been reported in ( 1 ) 40%-69%, ( 2 ) 25%-47%, ( 3 ) 9%-52%, and ( 4 ) 25%-30% in patients with CKD, on hemodialysis, on PD, or in KTRs, respectively. Fatigue is a complex symptom that has been reported in patients with CKD, ESKD, and in KTRs and can be associated with sleep disorders. Fatigue and sleep disorders have been associated with negative outcomes such as progression of CKD, increased risk of morbidity, mortality, and lower health-related quality of life. In this review, we highlight nonpharmacologic and pharmacologic options for treatment of these sleep disorders. Specifically, the diagnosis and evaluation, epidemiology, risk factors and associations, outcomes (such as CKD progression, morbidity, and mortality), treatment, and post-transplant outcomes for sleep disorders (insomnia, RLS, and SA) and fatigue will be discussed.

History of Sleep Disorders in Chronic Kidney Disease: First Approach

OBJECTIVES

In this study, we examined the history of sleep disorders in chronic kidney disease, 60 years after the advent of hemodialysis and renal transplant of genetically nonrelated organs, which have spurred a critical mass of data.

MATERIALS AND METHODS

We analyzed selected literature on sleep disorders in chronic kidney disease from 1959 onward.

RESULTS

Sleep disturbances are present in the general population. They cause loss of renal function and progressive nephron loss. Insomnia, sleep apnea, restless leg syndrome, and periodic limb movements represent sleep disturbances in chronic kidney disease. These symptoms manifest early in chronic kidney disease and are a rule in patients on dialysis and kidney transplant recipients. Sleep disturbances cause fatigue, excessive daily sleepiness, impaired daytime function, impaired health-related quality of life, increased morbidity, and increased mortality.

CONCLUSIONS

Sleep disorders affect most patients with chronic kidney disease. No ascertained pharmacological therapy exists, and even a successful transplant does not totally restore a refreshing sleep. Longer nocturnal hemodialysis is of benefit. Sleep apnea may be cured with continuous positive airway pressure.

What are the sleep characteristics among early kidney transplant recipients? An objective and subjective measurement from China

OBJECTIVE

To evaluate the sleep quality by self-reported questionnaires and polysomnography (PSG) among early kidney transplant recipients (KTRs) and to further explore their correlation.

DESIGN

This was a prospective and cross-sectional analysis of the sleep characteristics among early kidney transplant recipients through an objective and subjective measurement.

PARTICIPANTS

Patients with end stage renal disease on the transplant waiting list and after kidney transplantation were from a major organ transplantation center in Southern China (n = 83).

PRIMARY AND SECONDARY OUTCOME MEASUREMENTS

Objective outcomes: PSG, noise and light. Subjective outcomes: demographic and clinical questionnaires, self-reported pain and Richards Campbell sleep questionnaire (RCSQ). After agreement with the informed consent, participants first completed demographic and clinical questionnaires, then worn the PSG within 5-10 days after kidney transplantation. Both noise, light and self-reported pain were monitored during sleep. After completion of PSG, the RCSQs were filled out next morning.

RESULTS

A total of 298 patients were recruited and 83 participants were finally analyzed. The total RCSQ mean score was 51.0±18.9mm. The prevalence of poor sleep quality among early KTRs was 45.1%. Most of PSG characteristics were significantly correlated with their corresponding RCSQ items. And the total RCSQ scores were significantly correlated with the number of awakenings, the N2 percentage and the total sleep time (r = 0.79, 0.47 and 0.40, P<0.05) respectively. Noise was a statistically significant factor affecting the subjective sleep quality.

CONCLUSIONS

The sleep quality in early KTRs measured by both PSG and RCSQ exhibits consistency with each other. Sleep disruption always remains a substantial problem and is affected by self-reported noise among early KTRs. The RCSQ is easily applicable and interpretable so that it can be used for future daily clinical practice.

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.

Obstructive sleep apnea, sleep duration and chronic kidney disease in patients with coronary artery disease

BACKGROUND

Limited evidence is available addressing the potential role of sleep disorders on renal function. Here, we aimed to explore the associations of obstructive sleep apnea (OSA) and sleep duration (SD) with renal function in subjects with high cardiovascular risk.

METHODS

Consecutive subjects with coronary artery disease (CAD) underwent clinical evaluation, sleep study to define OSA and one-week wrist actigraphy to objectively measure SD. OSA was defined by an apnea-hypopnea index (AHI) of ≥15 events/hour. The estimated glomerular filtration rate (eGFR) was calculated using the CKD-EPI equation. We analyzed the associations of OSA and SD with continuous eGFR values and according to the presence of CKD (eGFR<60 mL/min/1.73 m²) after adjusting for multiple confounding factors.

RESULTS

We studied 242 subjects (62.8% men). The frequency of OSA was 55.4% and the median SD was 412.8 (363.4-457.25) min. There was no difference in the eGFRs between participants with and without OSA (69.3 ± 19.1 vs. 74.6 ± 19.3 mL/min/1.73 m², p = 0.72) and the rate of eGFR <60 mL/min/1.73 m² (34.3% vs. 25.9%; p = 0.21). Similarly, we did not find differences in patients in eGFR for those with SD ≥ 6 h versus SD < 6 h (72.5 ± 20.3 vs. 71.4 ± 19.1 mL/min/1.73 m², p = 0.72). In the linear regression analysis, AHI was independently associated with an eGFR<60 mL/min/1.73 m² in the unadjusted model [-0.15 (-0.27 to -0.04)], (P = 0.01), but not in the adjusted models. Analyses of continuous SD or the stratification in SD ≥ 6 h or <6 h also revealed neutral results on eGFR.

CONCLUSION

OSA severity and SD were not independently associated with CKD in subjects with CAD.

Sleep Apnea as a Cardiorenal Risk Factor in CKD and Renal Transplant Patients

BACKGROUND

Chronic kidney disease (CKD) is a public health priority of increasing concern worldwide. Sleep apnea (SA) of moderate-to-severe degree has a 3-9% prevalence in women and 10-17% in men in the general population.

SUMMARY

In CKD patients, the prevalence of SA parallels the decline of the GFR being 27% in CKD patients with a GFR of >60 mL/min/1.73 m2 and 57% in patients with end-stage kidney disease (ESKD). In the early CKD stages, fluid overload is probably the sole risk factor for SA in this population. At more severe CKD stages, disturbed central and peripheral chemosensitivity and the accumulation of uremic toxins might contribute to SA. Still, there is no direct evidence supporting this hypothesis in human studies. Observational studies coherently show that SA is a risk factor for CKD incidence and CKD progression as well as for cardiovascular disease and death in this population. However, there is no randomized clinical trial testing continuous positive airway pressure or other interventions documenting that attenuation of SA may have a favorable effect on renal and cardiovascular outcomes in CKD and ESKD patients. However, most likely, the causal nature of the association between SA and cardiorenal outcomes remains unproven. Renal transplantation is the most effective treatment of SA in patients with ESKD, but this disturbance re-emerges on long-term observation in this population. However, after renal transplantation, SA does not seem to be a predictor of adverse health outcomes.

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.

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.

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.

Sleep disorders: Serious threats among kidney transplant recipients

In patients with chronic kidney disease (CKD) and kidney transplant recipients who continue to have some degree of CKD, the prevalence of sleep-related disorders is very high. Common sleep disorders in both groups include insomnia, sleep-disordered breathing (SDB), restless legs syndrome (RLS), excessive daytime sleepiness (EDS), and others. Depending on the kidney graft function, some patients see sleep disorders resolve after kidney transplantation, while others continue to have persistent sleep disorders or develop new ones. Kidney transplant recipients (KTRs) are unique patients due to the presence of a single kidney, the use of immunosuppressive medications, and other comorbidities including obesity, a high risk of cardiovascular disease, malignancy, and the anxiety of losing their allograft. All of these factors contribute to the risk for sleep disorders. CKD and sleep disorders have a bidirectional relationship; that is, CKD may increase the risk of sleep disorders and sleep disorders may increase the risk of CKD. Obstructive sleep apnea (OSA) is the most common form of SDB and is known to alter renal hemodynamics. OSA leads to hypoxemia and sleeps fragmentation, which activates the sympathetic nervous system. This activates the renin-angiotensin-aldosterone system and ultimately alters cardiovascular hemodynamics. Sleep disorders may have deleterious effects on the kidney allograft and proper screening and management are important for both graft and patient survival.

Association of obstructive sleep apnoea with the risk of vascular outcomes and all-cause mortality: a meta-analysis

OBJECTIVE

This study aimed to conduct a meta-analysis to explore and summarise the evidence regarding the association between obstructive sleep apnoea (OSA) and the subsequent risk of vascular outcomes and all-cause mortality.

METHODS

Electronic databases PubMed, Embase and the Cochrane Library were searched to identify studies conducted through May 2016. Prospective cohort studies that reported effect estimates with 95% CIs of major adverse cardiac events (MACEs), coronary heart disease (CHD), stroke, cardiac death, all-cause mortality and heart failure for different levels versus the lowest level of OSA were included.

RESULTS

A total of 16 cohort studies reporting data on 24 308 individuals were included. Of these, 11 studies reported healthy participants, and the remaining five studies reported participants with different diseases. Severe OSA was associated with an increased risk of MACEs (relative risk (RR): 2.04; 95% CI 1.56 to 2.66; P<0.001), CHD (RR: 1.63; 95% CI 1.18 to 2.26; P=0.003), stroke (RR: 2.15; 95% CI 1.42 to 3.24; P<0.001), cardiac death (RR: 2.96; 95% CI 1.45 to 6.01; P=0.003) and all-cause mortality (RR: 1.54; 95% CI 1.21 to 1.97; P<0.001). Moderate OSA was also significantly associated with increased risk of MACEs (RR: 1.16; 95% CI 1.01 to 1.33; P=0.034) and CHD (RR: 1.38; 95% CI 1.04 to 1.83; P=0.026). No significant association was found between mild OSA and the risk of vascular outcomes or all-cause mortality (P>0.05). Finally, no evidence of a factor-specific difference in the risk ratio for MACEs among participants with different levels of OSA compared with those with the lowest level of OSA was found.

CONCLUSIONS

Severe and moderate OSAs were associated with an increased risk of vascular outcomes and all-cause mortality. This relationship might differ between genders. Therefore, further large-scale prospective studies are needed to verify this difference.

Association of symptoms of insomnia and sleep parameters among kidney transplant recipients

OBJECTIVE

Insomnia complaints are frequent among kidney transplant (kTx) recipients and are associated with fatigue, depression, lower quality of life and increased morbidity. However, it is not known if subjective insomnia symptoms are associated with objective parameters of sleep architecture. Thus, we analyze the association between sleep macrostructure and EEG activity versus insomnia symptoms among kTx recipients.

METHODS

Participants (n₁=100) were selected from prevalent adult transplant recipients (n₀=1214) followed at a single institution. Insomnia symptoms were assessed by the Athens Insomnia Scale (AIS) and standard overnight polysomnography was performed. In a subgroup of patients (n₂=56) sleep microstructure was also analyzed with power spectral analysis.

RESULTS

In univariable analysis AIS score was not associated with sleep macrostructure parameters (sleep latency, total sleep time, slow wave sleep, wake after sleep onset), nor with NREM and REM beta or delta activity in sleep microstructure. In multivariable analysis after controlling for covariables AIS score was independently associated with the proportion of slow wave sleep (β=0.263; CI: 0.026-0.500) and REM beta activity (β=0.323; CI=0.041-0.606) (p<0.05 for both associations).

CONCLUSIONS

Among kTx recipients the severity of insomnia symptoms is independently associated with higher proportion of slow wave sleep and increased beta activity during REM sleep but not with other parameters sleep architecture. The results suggest a potential compensatory sleep protective mechanism and a sign of REM sleep instability associated with insomnia symptoms among this population.

Habitual sleep and kidney function in chronic kidney disease: the Chronic Renal Insufficiency Cohort study

Physiological evidence suggests that sleep modulates kidney function. Our objective was to examine the cross-sectional association between kidney function and objectively-estimated habitual sleep duration, quality and timing in a cohort of patients with mild to moderate chronic kidney disease. This study involved two US clinical centers of the Chronic Renal Insufficiency Cohort (CRIC) study, including 432 participants in a CRIC ancillary sleep study. Habitual sleep duration, quality and timing were measured using wrist actigraphy for 5-7 days. Validated sleep questionnaires assessed subjective sleep quality, daytime sleepiness and risk of sleep apnea. Kidney function was assessed with the estimated glomerular filtration rate using the Chronic Kidney Disease Epidemiology Collaboration equation, and the urinary protein to creatinine ratio. Lower estimated glomerular filtration rate was associated with shorter sleep duration (-1.1 mL min^-1  1.73 m^-2 per hour less sleep, P = 0.03), greater sleep fragmentation (-2.6 mL min^-1  1.73 m^-2 per 10% higher fragmentation, P < 0.001) and later timing of sleep (-0.9 mL min^-1  1.73 m^-2 per hour later, P = 0.05). Higher protein to creatinine ratio was also associated with greater sleep fragmentation (approximately 28% higher per 10% higher fragmentation, P < 0.001). Subjective sleep quality, sleepiness and persistent snoring were not associated with estimated glomerular filtration rate or protein to creatinine ratio. Thus, worse objective sleep quality was associated with lower estimated glomerular filtration rate and higher protein to creatinine ratio. Shorter sleep duration and later sleep timing were also associated with lower estimated glomerular filtration rate. Physicians treating patients with chronic kidney disease should consider inquiring about sleep and possibly sending for clinical sleep assessment. Longitudinal and interventional trials are needed to understand causal direction.

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.

Association of incident obstructive sleep apnoea with outcomes in a large cohort of US veterans

RATIONALE

There is a paucity of large cohort studies examining the association of obstructive sleep apnoea (OSA) with clinical outcomes including all-cause mortality, coronary heart disease (CHD), strokes and chronic kidney disease (CKD).

OBJECTIVES

We hypothesised that a diagnosis of incident OSA is associated with higher risks of these adverse clinical outcomes.

METHODS, MEASUREMENTS

In a nationally representative cohort of over 3 million (n=3 079 514) US veterans (93% male) with baseline estimated glomerular filtration rate (eGFR)≥60 mL/min/1.73 m(2), we examined the association between the diagnosis of incident OSA, treated and untreated with CPAP, and: (1) all-cause mortality, (2) incident CHD, (3) incident strokes, (4)incident CKD defined as eGFR<60 mL/min/1.73 m(2), and (5) slopes of eGFR.

MAIN RESULTS

Compared with OSA-negative patients, untreated and treated OSA was associated with 86% higher mortality risk, (adjusted HR and 95% CI 1.86 (1.81 to 1.91) and 35% (1.35 (1.21 to 1.51)), respectively. Similarly, untreated and treated OSA was associated with 3.5 times (3.54 (3.40 to 3.69)) and 3 times (3.06 (2.62 to 3.56)) higher risk of incident CHD; 3.5 times higher risk of incident strokes (3.48 (3.28 to 3.64) and 3.50 (2.92 to 4.19)) for untreated and treated OSA, respectively. The risk of incident CKD was also significantly higher in untreated (2.27 (2.19 to 2.36)) and treated (2.79 (2.48 to 3.13)) patients with OSA. The median (IQR) of the eGFR slope was -0.41 (-2.01 to 0.99), -0.61 (-2.69 to 0.93) and -0.87 (-3.00 to 0.70) mL/min/1.73 m(2) in OSA-negative patients, untreated OSA-positive patients and treated OSA-positive patients, respectively.

CONCLUSIONS

In this large and contemporary cohort of more than 3 million US veterans, a diagnosis of incident OSA was associated with higher mortality, incident CHD, stroke and CKD and with faster kidney function decline.