Reversal of sleep apnea hypopnea syndrome in end-stage renal disease after kidney transplantation

Sleep disorders in chronic kidney disease

Sleep disorders are highly prevalent in chronic kidney disease (CKD) but are often under-recognized. Restless legs syndrome, which is common in CKD owing to issues with dopamine metabolism and is exacerbated by iron deficiency and uraemia, can lead to poor sleep quality and increased daytime fatigue. Insomnia is also prevalent in CKD, particularly in patients requiring dialysis, with increased sleep latency and sleep fragmentation being reported. The cause of insomnia in CKD is multifactorial - poor sleep habits and frequent napping during dialysis, uraemia, medications and mood disorders have all been suggested as potential contributing factors. Sleep apnoea and CKD are also now recognized as having a bi-directional relationship. Sleep apnoea is a risk factor for accelerated progression of CKD, and fluid overload, which is associated with kidney failure, can lead to both obstructive and central sleep apnoea. The presence of obstructive sleep apnoea in CKD can exacerbate the already heightened cardiovascular morbidity and mortality in these patients, as well as leading to daytime fatigue and reduced quality of life. Increased awareness, timely diagnosis and appropriate therapeutic interventions are essential to reduce the negative impact of sleep disorders in patients with kidney disease.

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.

Sleep-Disordered Breathing and 24-Hour Ambulatory Blood Pressure Monitoring in Renal Transplant Patients: Longitudinal Study

Background Sleep-disordered breathing (SDB) is considered a strong risk factor for hypertension in the general population. This disturbance is common in end-stage kidney disease patients on long-term hemodialysis and improves early on after renal transplantation. Whether SDB may be a risk factor for hypertension in renal transplant patients is unclear. Methods and Results We investigated the long-term evolution of simultaneous polysomnographic and 24-hour ambulatory blood pressure (BP) monitoring recordings in a cohort of 221 renal transplant patients. Overall, 404 paired recordings were made over a median follow-up of 35 months. A longitudinal data analysis was performed by the mixed linear model. The apnea-hypopnea index increased from a median baseline value of 1.8 (interquartile range, 0.6-5.0) to a median final value of 3.6 (interquartile range, 1.7-10.4; P=0.009). Repeated categorical measurements of the apnea-hypopnea index were directly associated with simultaneous 24-hour, daytime, and nighttime systolic ambulatory BP monitoring (adjusted analyses; P ranging from 0.002-0.01). In a sensitivity analysis restricted to 139 patients with at least 2 visits, 24-hour, daytime, and nighttime systolic BP significantly increased across visits (P<0.05) in patients with worsening SDB (n=40), whereas the same BP metrics did not change in patients (n=99) with stable apnea-hypopnea index. Conclusions In renal transplant patients, worsening SDB associates with a parallel increase in average 24-hour, daytime, and nighttime systolic BP. These data are compatible with the hypothesis that the link between SDB and hypertension is causal in nature. Clinical trials are, however, needed to definitively test this hypothesis.

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

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

Impact of kidney transplantation on sleep apnea severity: A prospective polysomnographic study

Fluid overload has been associated with a high prevalence of sleep apnea (SA) in patients with end-stage kidney disease (ESKD). In this prospective study, we hypothesized that improvement in kidney function and hydration status after kidney transplantation (Tx) may result in an improvement in SA severity. A total of 196 patients on the kidney Tx waiting list were screened for SA using home nocturnal polysomnography (PSG) to measure the apnea-hypopnea index (AHI) and underwent bioimpedance to assess body composition. Of 88 participants (44.9%) with SA (AHI ≥ 15/h), 42 were reassessed 6 months post-Tx and were compared with 27 control patients. There was a significant, but small, post-Tx improvement in AHI (from 44.2 ± 24.3 to 34.7 ± 20.9/h, P = .02) that significantly correlated with a reduction in fluid overload (from 1.8 ± 2.0 to 1.2 ± 1.2 L, P = .02) and body water (from 54.9% to 51.6%, P = .003). A post-Tx increase in body fat mass (from 26% to 30%, P = .003) possibly blunted the beneficial impact of kidney Tx on SA. All parameters remained unchanged in the control group. In conclusion, SA is a frequent condition in ESKD patients and partially improved by kidney Tx. We suggest that SA should be systematically assessed before and after kidney Tx. ClinicalTrials.gov Identifier: NCT02020642.

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.

Nocturnal dialysis improves sleep apnea more than daytime dialysis: a meta-analysis of crossover studies

PURPOSE

To systematically review the literature for articles evaluating differences in polysomnography (PSG) data when patients are on primarily daytime hemodialysis (conventional hemodialysis or continuous ambulatory peritoneal dialysis) versus nocturnal hemodialysis (nocturnal hemodialysis or nocturnal peritoneal dialysis). Then to perform a meta-analysis on the available PSG data, specifically evaluating differences in apnea hypopnea index (AHI) and mean saturation of oxygen (SpO₂) between these two groups.

METHODS

Two authors systematically searched MEDLINE/Pubmed, Scopus, EMBASE, CINAHL, and Cochrane. Searches were performed through December 6, 2018.

RESULTS

A total of four adult crossover studies (91 patients, age 50.4 ± 12.4, BMI 25.1 ± 5.3) reported PSG data. The daytime hemodialysis (DHD) and nocturnal hemodialysis (NHD) AHI decreased from 24.6 ± 18.2 to 12.6 ± 11.8 (events/hour) with a mean difference of -11.9 [95% CI -13.47, -10.37], Z score of 15.07 (P < 0.00001). The standardized mean difference was -1.35 [95% CI -2.70, 0.01]. Two studies reported mean SpO₂ changes during PSG. The DHD and NHD SpO₂ increased from 92.7 ± 2.4 to 94.7 ± 2.2 with a mean difference of 2.26 [95% CI -0.18, 4.71], Z score 1.82 (P = 0.07).

CONCLUSION

In the current literature, nocturnal hemodialysis improves AHI more than daytime hemodialysis. A trend towards improvement in mean SpO₂ with nocturnal dialysis was noted, but did not reach statistical significance. Consideration can be given for transitioning patients who have end stage renal disease and sleep apnea from daytime to nocturnal hemodialysis as an adjunct to other treatment modalities.

Snoring and incident chronic kidney disease: a community-based prospective cohort study

OBJECTIVES

Previous studies have shown that symptoms of sleep-disordered breathing are associated with metabolic derangements and vascular disease development. However, the relationship between snoring and renal function is not well investigated. The association between snoring and the development of incident chronic kidney disease (CKD) in subjects with normal renal function was evaluated.

DESIGN

Prospective cohort study.

SETTING

Ansung (rural community) and Ansan (urban community) cities.

PARTICIPANTS

Community-based cohort participants aged 40-69 years.

METHODS

A total of 9062 participants in the Ansung-Ansan cohort study were prospectively followed up from 2001 to 2014. The participants were classified into three groups: non-snorer, <1 day/week and ≥1 day/week. The main outcome was incident CKD, which was defined as an estimated glomerular filtration rate of <60 mL/min/1.73 m² during the follow-up period.

PRIMARY OUTCOME

Incident CKD.

RESULTS

The mean subject age was 52.0±8.9 years, and 4372 (48.2%) subjects were male. The non-snorer,<1 day/week and ≥1 day/week groups included 3493 (38.5%), 3749 (41.4%), and 1820 (20.1%) subjects, respectively. Metabolic syndrome was more prevalent in the snoring groups than in the non-snoring group. Snoring frequency showed a significant positive relationship with age, waist:hip ratio, fasting glucose, total cholesterol (Tchol) and low-density lipoprotein cholesterol. During a mean follow-up of 8.9 years, 764 (8.4%) subjects developed CKD. Cox proportional hazards model analysis revealed that the risk of CKD development was significantly higher in subjects who snored ≥1 day/week than in non-snorers, even after adjustments for confounding factors (HR 1.23, 95% CI 1.09 to 1.38, p<0.01).

CONCLUSION

Snoring may increase the risk of CKD development in subjects with normal renal function.

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.

Effect of nocturnal hemodialysis on sleep parameters in patients with end-stage renal disease: a systematic review and meta-analysis

Introduction

Recently, a small but growing literature has depicted the beneficial effects of nocturnal hemodialysis (NHD) over conventional hemodialysis (CHD) in the fields of sleep disorders such as sleep apnea. The impact of various dialysis models on sleep disorders, however, has not been determined. The objective of our meta-analysis is to examine the potential effects of NHD, compared with CHD, on sleep disorders in HD patients.

Methods

Several electronic databases including PubMed, EMBASE, Cochrane Central Register of Controlled Trials, ClinicalTrials.gov and CNKI were searched, using the search terms “nocturnal” (or “nightly”) and “dialysis” (or “hemodialysis” or “renal dialysis”) from the earliest available date of indexing to March 2018. Two authors independently extracted data, evaluated the study quality, and conducted random-effects meta-analyses using STATA 12.0.

Results

Of 1789 potentially relevant citations, 9 fulfilled eligibility criteria, consisting of 6 single-arm studies (comparing pre- and post-intervention outcomes), 1 observational study, and 2 randomized controlled trials (a total of 286 participants). Regarding objective sleep assessments, conversion from CHD to NHD resulted in a significant reduction in the AHI (Mean difference was -14.90; 95% CI, -20.12 to -9.68), a significant increase of SaO2 (Mean difference was 1.38%; 95% CI, 0.35% to 2.42%), and a significant decrease of TST (Mean difference was -0.31; 95% CI, -0.47 to -0.15). The trends were even stronger in the HD patients with sleep disorders. However, regarding subjective sleep assessments, improved sleep quality was found in the prospective pre-post intervention studies and cohort studies, while no significant improvements were found in the randomized controlled trials.

Conclusion

Although a significant improvement of sleep apnea was observed by switching from CHD to NHD, it may not yield a net benefit in overall subjective sleep quality.

Insomnia is Associated with Systolic Hypertension in Uremic Patients on Hemodialysis

A newly developed questionnaire was administered to 140 hemodialyzed patients (82 M and 58 F) who have achieved adequate anemia correction according to the best guidelines with the aim: to evaluate the prevalence of clinical/subclinical dyssomnias in these patients; to study the influence of the dialytic shift (morning versus afternoon schedules) on sleep duration and disturbancies; and to evaluate the relationship between clinical sleep disorders and blood pressure values in uremic patients. Results indicated that 85% of uremic patients undergoing hemodialysis complain of clinical insomnia (frequent, persistent and associated with daytime consequences) or subclinical sleep disorders; patients dialyzing in the morning sleep significantly less during the night preceding the treatment, than those dialyzing in the afternoon; older patients complaining of clinical insomnia have a higher risk of failure to achieve target-optimal values in systolic blood pressure.

Quality of sleep in renal transplant recipients and patients on hemodialysis

BACKGROUND

Sleep disorders are very common in patients with chronic kidney disease and they may not always subside after kidney transplantation.

AIM AND METHODS

The aim of this cross-sectional study was to evaluate the self-reported quality of sleep, insomnia problems in particular, and examine the factors that disturb sleep of kidney transplant recipients (KTx: n=152) in comparison to age- and sex-matched patients on dialysis (HD: n=67) and participants with normal renal function (NOR: n=49), through the administration of the Athens Insomnia Scale (AIS) at least six months after transplantation. Clinical and laboratory data, as well as health-related quality of life, depression, anxiety, post-traumatic stress symptoms, and the presence of restless legs syndrome (RLS) and pruritus were investigated in relation to sleep problems.

RESULTS

The highest mean AIS score was observed in the transplant patients (KTx: 4.6±13.3 vs. HD: 3.8±8.1 vs. NOR: 2.4±10.2); both KTx and HD patients had a lower quality of sleep compared to participants with normal renal function. Multiple linear regression analysis showed that the determinants of the total AIS score were the frequency of post-traumatic stress symptoms, depression, RLS, diastolic blood pressure, and pain (all p<0.0001).

CONCLUSION

Although amelioration of renal function post-transplantation improves several aspects of quality of life, it does not seem to have a beneficial effect on self-reported sleep.

Emerging co-morbidities of obstructive sleep apnea: cognition, kidney disease, and cancer

Obstructive sleep apnea (OSA) causes daytime fatigue and sleepiness, and has an established relationship with cardiovascular and metabolic disease. Recent years have seen the emergence of an evidence base linking OSA with an increased risk of degenerative neurological disease and associated cognitive impairment, an accelerated rate of decline in kidney function with an increased risk of clinically significant chronic kidney disease (CKD), and with a significantly higher rate of cancer incidence and death. This review evaluates the evidence base linking OSA with these seemingly unrelated co-morbidities, and explores potential mechanistic links underpinning their development in patients with OSA, including intermittent hypoxia (IH), sleep fragmentation, sympathetic excitation, and immune dysregulation.

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.

Altered sleep structure in patients with end-stage renal disease

OBJECTIVE

Although symptoms of sleep disturbances are widely recognized in end-stage renal disease (ESRD), the effect of uremia on sleep structure has not been well investigated. We hypothesized that compared to individuals without ESRD, those with ESRD would have altered sleep structure after controlling for the severity of sleep apnea (SA).

METHODS

We studied 57 ESRD patients (42 men) and 57 controls (46 men) who had undergone polysomnography. Control subjects were matched to the ESRD patients by age, body mass index (BMI), frequency of periodic leg movements per hour of sleep, and the frequency of apneas and hypopneas per hour of sleep [apnea-hypopnea index (AHI)].

RESULTS

The AHI and the percentage of patients with an AHI ≥15 were similar between ESRD and control groups. However, total (p = 0.002), rapid eye movement (REM) (p = 0.007), and non-REM (p = 0.022) sleep times were lower in ESRD patients than in the control group. In a multivariable analysis adjusted for age, sex, AHI, BMI, arousal index, and diabetes, ESRD remained independently associated with lower REM (p = 0.021) and total sleep times (p = 0.026).

CONCLUSION

ESRD is independently associated with reduced total and REM sleep times after controlling for the severity of SA and other variables. Although we could not identify the cause of reduced sleep times, these could be related to uremia or fluid overload or both. Accordingly, our data provide a strong rationale for examining the effects of intensifying dialysis on sleep structure in ESRD patients.

Sleep apnea syndrome and restless legs syndrome in kidney transplant recipients

Background:

This study was aimed to evaluate the prevalence of obstructive sleep apnea (OSA) and restless legs syndrome (RLS) in patients with end-stage renal disease (ESRD) after kidney transplantation.

Materials and Methods:

Two hundred kidney transplant recipients were enrolled in this cross-sectional study. Data on age, gender, etiology of ESRD, history of previous kidney transplantation, serum creatinine, and the presence or absence of OSA and RLS were collected. Symptoms of RLS were identified using the RLS questionnaire which was completed by the patients. The Berlin questionnaire and polysomnography were used for diagnosing OSA.

Results:

The mean age of the studied patients was 45.86 ± 10.24 years. The prevalence of OSA was 26% (52 of 200 studied patients) and of RLS was 51.5% (103 of 200 studied patients). Majority of the patients with high-risk OSA were male and significantly older than the patients with low-risk OSA (P < 0.05). The prevalence of RLS was higher in patients with high-risk OSA and a higher level of creatinine compared to that in those with a low risk of OSA (P < 0.0001). Level of creatinine in patients with positive RLS was significantly higher than in those with negative RLS (P < 0.0001). OSA was observed in almost 42% of patients with positive RLS, compared to 9% of patients with negative RLS (P < 0.0001).

Conclusion:

In summary, our results indicate that the prevalence of OSA and RLS in kidney transplant recipients was higher than in the general population. Also, there was a significant association between OSA and RLS in these patients.

Effect of Renal Transplantation in Restless Legs Syndrome

OBJECTIVES

Restless legs syndrome is a disorder in which patients have irresistible urge to move legs during rest. Restless legs syndrome seems to be common in end-stage renal disease. After a successful renal transplant, symptoms ameliorate with renal function improvement and restless legs syndrome is seen less in this population. Here, we aimed to investigate restless legs syndrome frequency and associated factors in renal transplant patients.

MATERIALS AND METHODS

In a cross-sectional study with 193 patients (116 hemodialysis patients, 45 transplant patients, and 32 controls), the presence of restless legs syndrome was assessed using the Restless Legs Syndrome Questionnaire. Medical history, demographic, and laboratory data were collected from the patients' medical records. Patients were questioned about the presence of restless legs syndrome using the Restless Legs Syndrome Questionnaire. Patients were evaluated with Beck Depression Scale for depression and Pittsburgh tests for sleep disturbances.

RESULTS

While the rate of restless legs syndrome was similar between transplants and controls, it was significantly greater in hemodialysis patients. Hemodialysis patients and controls had similar depression scores that were higher compared with transplant patients. Pittsburgh score was similar in transplant patients and controls and significantly increased in the hemodialysis patients. The rate of insomnia was significantly higher in the hemodialysis patients compared with the other 2 groups. Logistic regression analysis revealed independent correlates of restless legs syndrome as insomnia, Beck depression score, and being on hemodialysis. Linear regression analysis showed that independent correlates of higher Pittsburgh score were higher depression score, higher age, and presence of restless legs syndrome.

CONCLUSIONS

The prevalence of restless legs syndrome is significantly lower in transplant patients than it is in patients on maintenance dialysis. In renal transplant patients, restless legs syndrome frequency was found to be lower because of improved renal functions (normalization of uremia), psychological symptoms, and sleep disturbances.

Obstructive sleep apnea syndrome is related to the progression of chronic kidney disease

BACKGROUND AND AIM

Obstructive sleep apnea syndrome (OSAS) is an independent risk factor for the development of cardiovascular events and hypertension. The possible causes are oxygen desaturation due to hypopnea, increased cytokine levels and insulin resistance. All these risk factors also have a role in the progression of chronic kidney disease (CKD). The aim of this study was to determine the relationship between OSAS and the severity of CKD.

MATERIALS AND METHODS

We retrospectively evaluated the medical records of 175 subjects who were admitted for the polysomnography study. OSAS was diagnosed by polysomnography if Apnea-Hypopnea Index (AHI) > 5 and glomerular filtration rate (GFR) was calculated with Cockcroft-Gault formula. According to AHI, individuals with AHI < 5 were recruited as group 1 (OSAS negative group), those with AHI = 5-15 group 2 (mild OSAS group), those with AHI = 15-30 group 3 (moderate OSAS group), and those with AHI > 30 group 4 (severe OSAS group).

RESULTS

Of the subjects, 117 (67%) were men, 58 (33%) were women and the mean age was 54.0 ± 12.1 years. There were 28 (14.3%), 18 (10.3%), 35 (20.0%) and 97 (55.4%) patients in groups 1, 2, 3 and 4 respectively. The prevalence of diabetes mellitus and hypertension and body mass index was significantly higher in severe OSAS group (P < 0.05). A significant decrease in GFR was detected when the severity of OSAS increased (group 1 = 50.0 ± 11.8, group 2 = 44.8 ± 15.9, group 3 = 40.8 ± 14.7, group 4 = 38.8 ± 16.0; P for trend < 0.001).

CONCLUSION

In the light of the present study, we speculate that OSAS is an independent risk factor for the progression of chronic kidney disease, which is a growing health problem. Further randomized-multicenter prospective studies are warranted to evaluate this relationship.

Sleep pattern in an experimental model of chronic kidney disease

The prevalence of sleep disorders is significantly elevated in chronic kidney disease (CKD) patients. Numerous factors likely contribute to the high prevalence of sleep problems in uremic patients. The objective of this study was to evaluate the long-term sleep pattern changes in uremic rats during disease progression. Sleep recordings of the rats were monitored during light and dark periods that lasted 12 h each. These recordings were performed on days 7, 30, 60, and 90 after CKD induction. Cardiovascular, hormonal, and biochemical changes were evaluated at these same time points in control and uremic rats. CKD progression was reflected by the presence of hypertension and progressive increases in urea, creatinine, and cholesterol levels. We also observed hormonal fluctuations of corticosterone and ACTH, which indicated a potential alteration in the hypothalamic-pituitary-adrenal axis in diseased rats. In addition, rats with CKD demonstrated fragmented sleep with a greater number of arousals and decreased sleep efficiency in the light period during disease progression. In the dark period, there was an initial increase in sleep efficiency in CKD rats, but after 90 days of CKD, these animals slept less compared with the control group. Collectively, these metabolic and cardiovascular changes were associated with the persistent alterations in sleep architecture observed in CKD rats.

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.

Resolution of sleep-disordered breathing in a dialysis-dependent child post-renal transplantation

This case alerts paediatricians and renal physicians to the potential for significant sleep-disordered breathing in children with renal disease, particularly those with end stage kidney disease requiring dialysis. In some cases, management of the underlying renal disease may result in amelioration of the sleep-disordered breathing. Proactive sleep history taking and formal sleep monitoring in experienced centres may be indicated for these children to limit morbidity, especially if respiratory support is indicated.

Sleep apnea is associated with cardiovascular risk factors among kidney transplant patients

BACKGROUND AND OBJECTIVES

We assessed the prevalence of obstructive sleep apnea (OSA) and its clinical correlates in a large sample of patients who received a kidney transplant (Tx). We also compared the prevalence of the disorder between dialysis patients who were on the waiting list for a Tx (WL) and Tx patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This was a cross-sectional study of 100 Tx and 50 WL patients who underwent one-night polysomnography (SLeep disorders Evaluation in Patients after kidney Transplantation [SLEPT] Study). Sociodemographic information and data about medication, comorbidity, and laboratory parameters were collected.

RESULTS

The prevalence of mild (apnea-hypopnea index [AHI] > or =5/h and <15/h), moderate (AHI > or =15/h and <30/h), and severe OSA (AHI > or =30/h) was 18, 11, and 14% in the Tx group and 28, 16, and 10% in the WL group, respectively. The AHI was significantly correlated with age (rho = 0.34), body mass index (rho = 0.45), neck circumference (rho = 0.4), abdominal circumference (rho = 0.51), and hemoglobin (rho = 0.24) in the Tx group. The proportion of Tx patients who were treated with three or more antihypertensive drugs was significantly higher in the OSA group (56 versus 31%; P = 0.022). Despite taking significantly more antihypertensive drugs, the average systolic BP was still higher in patients with versus without OSA (147 +/- 21 versus 139 +/- 18 mmHg; P = 0.059).

CONCLUSIONS

The prevalence of OSA is similar in Tx and WL patients and it may contribute to presence of hypertension in patients who receive a Tx.

Sleep disordered breathing in renal transplant patients

Sleep disordered breathing (SDB) is a prevalent, important nontraditional cardiovascular (CV) risk factor in end-stage renal disease patients. The prevalence of SDB in renal transplant patients is unknown. We compared polysomnographic studies in 163 transplant patients with matched samples in the general population and explored longitudinally the effect of return to dialysis after graft failure on SDB in three consecutive cases. Episodes of nocturnal hypoxemia, average and minimal O(2) saturation overnight in transplant patients did not differ from those in individuals in the general population matched for age, gender and body mass index (BMI). The prevalence of moderate-to-severe SBD in these patients did not exceed the estimated prevalence of the same disturbance in the general population. The respiratory disturbance index in transplant patients was directly associated with BMI (p < 0.001). In the longitudinal study all indicators of SDB coherently increased after transplant failure. The prevalence of SDB in transplant patients does not differ from that in well-matched individuals in the general population. The favorable effect of renal transplantation on CV risk may be at least partially explained by the lack of risk excess for SDB in this population. Longitudinal observations after transplant failure are compatible with the hypothesis that renal transplantation reverses SDB.

Improvement in sleep apnea during nocturnal peritoneal dialysis is associated with reduced airway congestion and better uremic clearance

BACKGROUND AND OBJECTIVES

Among peritoneal dialysis (PD) patients, nocturnal PD (NPD) is known to improve sleep apnea compared with continuous ambulatory peritoneal dialysis (CAPD), but the contributing factors are unclear.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

Thirty-eight incident ESRD patients underwent overnight polysomnography (PSG) during NPD and CAPD. Bioelectrical impedance analysis, magnetic resonance imaging of the upper airway, and urea kinetics (Kt/V) during sleep were measured on both occasions.

RESULTS

The prevalence of severe sleep apnea (apnea-hypopnea index, AHI > or = 15/h) was 21.1% during NPD, and 42.1% during CAPD. Mean AHI increased from 9.6 +/- 2.7/h during NPD to 21.5 +/- 4.2/h during CAPD. Both obstructive and central apnea worsened after conversion to CAPD. NPD achieved greater reductions in total body water, hydration fraction, and net ultrafiltration than CAPD during sleep. Overnight peritoneal Kt/V and creatinine clearance were lower after conversion. Both peritoneal Kt/V and peritoneal creatinine clearance correlated with AHI, as did their changes after conversion. Volumetric magnetic resonance imaging revealed reduced pharyngeal volumes and cross-sectional area, and tongue enlargement after conversion.

CONCLUSIONS

Improvement in sleep apnea during NPD versus CAPD is associated with better fluid and uremic clearance and reduced upper airway congestion during sleep.

Reduced renal function and sleep-disordered breathing in community-dwelling elderly men

BACKGROUND

Sleep-disordered breathing (SDB) may increase the risk of cardiovascular disease (CVD) and death in chronic kidney disease (CKD). However, the association between mild reductions in renal function and SDB is uncertain.

METHODS

We studied 508 community-dwelling men aged>or=67 years (mean 76.0+/-5.3) who were enrolled at the Minnesota site for the Minneapolis center of the Outcomes of Sleep Disorders in Older Men (MrOS) sleep study and had serum cystatin-C and creatinine measured coincident with overnight polysomnography. CKD was defined as estimated glomerular filtration rate (eGFR)<60 ml/min/1.73 m2 using Cockcroft-Gault (CG), modification of diet in renal disease (MDRD) and Mayo Clinic formulae. SDB was defined by a respiratory disturbance index (RDI)>or=15 events/h.

RESULTS

Mean cystatin-C was 1.21+/-0.30 mg/L, and mean creatinine was 1.09+/-0.23 mg/dL. Median RDI was 7.0 events/h (range 0-73). Higher quartiles of cystatin-C were associated with higher mean RDI (p for trend=0.007). This association persisted after adjustment for age and race (p for trend=0.03), but not after adjustment for body mass index (BMI, p for trend=0.34). After adjusting for age, race, BMI, diabetes, hypertension, and CVD, CKD defined by the Mayo Clinic formula, but not CG or MDRD, was associated with a higher odds of SDB [odds ratio (OR) 1.95, 95% confidence interval (CI) 1.04-3.65, p=0.04].

CONCLUSIONS

Older men with reduced renal function as defined by higher cystatin-C concentration have higher average RDI. This effect is explained by higher BMI in men with higher cystatin-C. CKD defined by the Mayo Clinic formula is independently associated with twofold higher odds for SDB. Therefore, reduced renal function may be associated with SDB in older men.

PSYCHOSOCIAL FACTORS IN PATIENTS WITH CHRONIC KIDNEY DISEASE: Sleepiness, Sleeplessness, and Pain in End-Stage Renal Disease: Distressing Symptoms for Patients

Symptoms are increasingly recognized as problematic for patients with end-stage renal disease (ESRD) treated with dialysis. Sleep disorders are common in ESRD patients treated with dialysis and are associated with patients' perceptions of quality of life, assessed by diverse measures, as well as depressive affect. Sleep disorders appear to be equally prevalent in peritoneal dialysis (PD) and hemodialysis (HD) patients. Treatment for sleep disorders in dialysis patients depends on establishing the diagnosis, often in a sleep laboratory, using polysomnography. Reversing coexistent medical and psychological disorders is important. The sleep apnea syndrome (SAS) can be treated with continuous positive airway pressure in dialysis patients, but conventional hemodialytic techniques have little effect on its severity. In contrast, nocturnal HD and transplantation appear to have important beneficial effects on sleep disordered breathing in ESRD patients. Although pain has been appreciated as a problem for ESRD patients for more than 20 years, few studies exist on this subject. Pain appears to be an underappreciated problem for ESRD patients. More research must be performed on the problem of pain in patients with chronic kidney disease (CKD).

Renal function and sleep-disordered breathing in older men

BACKGROUND

Sleep-disordered breathing (SDB) is common in severe chronic kidney disease (CKD) and may contribute to morbidity and mortality in this population. However, the association between mild to moderate CKD and likelihood of SDB is uncertain.

METHODS

We studied 2696 men >or=65 years (mean 73.0 +/- 5.5) enrolled in the Outcomes of Sleep Disorders in Older Men (MrOS Sleep) study who had serum creatinine (SCr) measured 3.4 years prior to overnight polysomnography (PSG). CKD was expressed as quartiles of estimated glomerular filtration rate (eGFR) using the four-variable Modification of Diet in Renal Disease (MDRD) formula. SDB was assessed using the respiratory disturbance index (RDI) with >or=4% oxygen desaturation.

RESULTS

Mean SCr was 0.99 +/- 0.20 mg/dl; 14.8% had eGFR <60 ml/min/1.73 m(2). Median RDI was 7.4 events/hour (inter-quartile range 2.6-15.8). Lower eGFR was not associated with higher mean RDI in the unadjusted model (P for trend = 0.180). There was evidence of an interaction between eGFR and age for the prediction of RDI; an association between lower eGFR and higher RDI was evident only among men <or=72 (median) years. Among this age group, however, the association was not statistically significant after further adjustment for body mass index (BMI) (P for trend = 0.278).

CONCLUSIONS

In this cohort of older community-dwelling men, reduced renal function was not associated with greater evidence of SDB, except among younger old men. However, this association was largely explained by higher BMI at lower eGFR. Further prospective study in younger populations is needed to clarify our findings.

High Prevalence of chronic kidney disease among patients with sleep related breathing disorder (SRBD)

Sleep apnea syndrome, a sleep-related breathing disorder (SRBD) of which obstructive sleep apnea syndrome (OSAS) is representative, is often associated with obesity, and therefore patients with SRBD might have a high prevalence of chronic kidney disease (CKD). However, the relationship between obesity and the prevalence of CKD has not yet been investigated in a large cohort of patients with SRBD. The Okinawa Nakamura Clinic Sleep Apnea Syndrome (ONSLEEP) registry contains records for all patients evaluated by full-scale polysomnography (PSG) from September 1990 to the end of 2003 (n=5,651). We studied the total of 4,056 (71.8%) of these patients who had an apnea hypopnea index (AHI) of more than 5 events per hour. The glomerular filtration rate (GFR) was estimated using the abbreviated Modification of Diet in Renal Disease equation in the 1,624 patients for whom serum creatinine data was obtained at the time of the PSG. We defined CKD as a GFR of less than 60 mL/min/1.73 m2. The mean age was 49.9+/-13.5 (mean+/-SD) years; the mean body mass index (BMI) was 28.4+/-5.0 (mean+/-SD) kg/m2. We compared the findings with those from participants in the 1993 general screening registry in Okinawa (n=94,267). From among the total 94,267 screening participants, we selected 7,454 subjects who were age- and sex-matched to the experimental group with SRBD; the ratio of cases to controls was thus approximately 1:4. CKD was detected in 496 (30.5%) patients, with SRBD a higher incidence than that in the screened population (9.1%); the adjusted odds ratio (95% confidence interval) was 4.542 (3.922-5.260, p<0.0001). In contrast to the screened population, the prevalence of CKD decreased as BMI increased (it was 35.7% in SRBD patients with a BMI<25.0 kg/m2, 31.4% in those with a BMI 25.0 to 29.9 kg/m2, and 25.2% in those with a BMI > or =30.0 kg/m2); in the controls the values were 8.1%, 10.5%, and 10.6%, respectively. Taken together, these results suggest that surveillance of CKD is warranted among SRBD patients, particularly those who are not obese.

Sleep apnea and dialysis therapies: things that go bump in the night?

Sleep apnea has been linked to excessive daytime sleepiness, depressed mood, hypertension, and cardiovascular disease in the general population. The prevalence of severe sleep apnea in the conventional thrice-weekly hemodialysis population has been estimated to be more than 50%. Sleep apnea leads to repetitive episodes of hypoxemia, hypercapnia, sleep disruption, and activation of the sympathetic nervous system. The hypoxemia, arousals, and intrathoracic pressure changes associated with sleep apnea lead to sympathetic activation, endothelial dysfunction, oxidative stress, and inflammation. Because sleep apnea has been shown to be widespread in the conventional dialysis population, it may be that sleep apnea contributes substantially to the sleepiness, poor quality of life, and cardiovascular disease found in this population. The causal links between conventional dialysis and sleep apnea remain speculative, but there are likely multiple factors related to volume status and azotemia that contribute to the high rate of severe sleep apnea in dialysis patients. Both nocturnal automated peritoneal dialysis and nocturnal hemodialysis have been associated with reduced severity of sleep apnea. Nocturnal dialysis modalities may provide tools to increase our understanding of the uremic sleep apnea and may also provide therapeutic alternatives for end-stage renal disease patients with severe sleep apnea. In conclusion, sleep apnea is an important, but overlooked, public health problem for the dialysis population. The impact of sleep apnea treatment in this high-risk population may include reduced sleepiness, better mood and blood pressure, and lowered risk of cardiovascular disease.