Central Sleep Apnea in Kidney Disease

Kidney transplantation: a possible solution to obstructive sleep apnea in patients with end-stage kidney disease

INTRODUCTION

Obstructive sleep apnea (OSA) is frequently reported among patients with chronic kidney disease resulting in considerable morbidity and mortality. OSA may cause repetitive stimulation of the sympathetic nervous system and elevations in pulmonary artery pressure leading to an elevated risk of cardiac and vascular complications in patients with chronic kidney disease. Furthermore, OSA is associated with progressive worsening of kidney injury and loss of renal function.

METHODS

In this systematic review and meta-analysis, we evaluated the effect of renal transplantation on the progression of OSA in patients with end-stage kidney disease.

RESULTS

The meta-analysis included eight studies with a total of 401 patients. Findings showed that kidney transplantation does not lead to a statistically significant effect on the apnea-hypopnea index (MD 2.6 events/hr, 95% CI -3.2 to 8.3, p = 0.21), total sleep time (MD 14.7 min/night, 95% CI -8.4 to 37.8, p = 0.76), sleep efficiency (MD 2.5%, 95% CI -1.4 to 6.3, p = 0.57), slow wave sleep (MD 0.4% of total sleep time, 95% CI -7.5 to 8.4, p = 0.05), and rapid eye movement sleep (MD 0.6% of total sleep time, 95% CI -2.2 to 3.3, p = 0.98). There was no statistically significant effect of kidney transplantation on OSA in patients with chronic renal disease.

Mortality Patterns Associated with Central Sleep Apnea among Veterans: A Large, Retrospective, Longitudinal Report

Rationale: Central sleep apnea (CSA) is associated with high mortality. Current knowledge stems from studies with limited sample size (fewer than 100 subjects) and in homogeneous populations such as heart failure (HF). Objectives: To address this knowledge gap, we compared the mortality pattern and time to death between the CSA and obstructive sleep apnea (OSA) patients in the large Veterans Health Administration patient population using the big data analytic approach. Methods: This is a retrospective study using national Veterans Health Administration electronic medical records from October 1, 1999, through September 30, 2020. We grouped the patients with underlying sleep disorders into CSA and OSA, using the International Classification of Diseases, Ninth and Tenth Revision codes. We applied Cox regression analysis to compare the mortality rate and hazard ratio (HR) among the two groups and adjusted HR by gender, race, body mass index (BMI), age, and Charlson Comorbidity Index. In CSA groups, a machine-learning algorithm was used to determine the most important predictor of time to death. Further subgroup analysis was also performed in patients that had comorbid HF. Results: Evaluation of patients resulted in 2,961 grouped as CSA and 1,487,353 grouped as OSA. Patients with CSA were older (61.8 ± 15.6 yr) than those with OSA (56.7 ± 13.9 yr). A higher proportion of patients with CSA (25.1%) died during the study period compared with the OSA cohort (14.9%). The adjusted HR was 1.53 (95% confidence interval [CI], 1.43-4.65). Presence of HF history of cerebrovascular disease, hemiplegia, and having a BMI less than 18.5 were among the highest predictors of mortality in CSA. The subgroup analysis revealed that the presence of HF was associated with increased mortality both in CSA (HR, 7.4; 95% CI, 6.67-8.21) and OSA (HR, 4.3; 95% CI, 4.26-4.34) groups. Conclusions: Clinically diagnosed CSA was associated with a shorter time to death from the index diagnostic date. Almost one-fifth of patients with CSA died within 5 years of diagnosis. The presence of HF, history of cerebrovascular disease and hemiplegia, male sex, and being underweight were among the highest predictors of mortality in CSA. CSA was associated with higher mortality than OSA, independent of associated comorbidity.

Predictors and consequences of residual apnea during positive airway pressure therapy

STUDY OBJECTIVES

Determine the risk factors for, and consequences of, residual apnea during long-term positive airway pressure (PAP) therapy for obstructive sleep apnea (OSA).

METHODS

A prospective cohort study of 195 subjects after a split-night polysomnogram. Estimation of residual respiratory events on PAP were done by both automated and manual scoring of data in EncoreAnywhere™. Clinical and polysomnographic predictors of residual apnea were estimated.

RESULTS

There were 166 and 101 patients still on PAP at the 3 and 12 months, respectively. Seventy four (44.6%) and 46 (45.5%) had a residual scored respiratory event index-flow (sREI_FLOW) ≥ 15/hour of use and 46 (45.5%) at the 3rd and 12th month, respectively. Treatment phase central apnea hypopnea index (TCAHI), a surrogate of high loop gain, was the main predictor for residual sREI_FLOW (β = 0.345, p: 0.025) at the 3rd and 12th month (β = 0.147, p: 0.020). TCAHI also predicted unstable breathing (U) %. The body mass index (hazard ratio [HR] 1.034, 95% CI 1.008-1.062, p: 0.012) and effective sREI_FLOW>15/hour in the first month (HR 2.477, 95% CI 1.510-4.065, p < 0.001) were the key predictors for drop out of PAP use at the 12th month. Effective sREI_FLOW>15/hour in the first month was also a predictor for median usage duration >4 h for 70% of the night at both the 3rd month (odds ratio [OR] 0.947, 95% CI 0.909-0.986, p: 0.008) and 12th month (OR 0.973, 95% CI 0.951-0.994, p: 0.014).

CONCLUSIONS

Treatment-phase CAHI predicts long-term residual apnea on PAP. High residual disease adversely impacts adherence.

High nocturnal periodic breathing reported by PAP adherence data predicts decompensation of heart failure

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) often coexists with heart failure (HF) and is commonly treated with positive airway pressure (PAP) therapy. Periodic breathing (PB) may be present in HF and is an indicator of poor prognosis, but there is no easy way to detect PB in an outpatient setting. However, it can be detected by analyzing PAP usage data. The study aimed to assess if high PB% detected by PAP machine could predict impending HF exacerbation and if better PAP adherence is associated with reduced hospitalization and mortality.

METHODS

We retrospectively reviewed medical records of 115 patients with OSA from the sleep clinic of our VA Medical Center. The cross-sectional data on demographics, labs, PAP adherence, PB% in the previous 30 days, echocardiogram in the previous 6 months, and hospitalizations and mortality in the subsequent 180 days were extracted. Based on left ventricular ejection fraction (LVEF), patients were classified into (1) HF with normal-midrange LVEF (LVEF ≥40%, n = 74) and (2) HF with reduced LVEF (LVEF < 40%, n = 41). Pairwise correlation and linear regressions were done to assess predictors of PB%. Binomial and logistic regressions assessed the relationship of PB% and PAP adherence with hospitalization from HF and all-cause mortality.

RESULTS

In the HF with reduced LVEF group, the mean PB% was 2.6 times higher (P < .001) and PAP adherence was 29% lower (P < .001). PB% positively correlated with brain natriuretic peptide level (r = .447, P < .01) and number of hospitalizations (r = .331, P < .01). Higher PB% negatively correlated with LVEF (r = -.423, P < .01) and estimated glomerular filtration rate (r = -.246, P < .01). Every 10% increase in PAP adherence decreased odds of hospitalization by 0.78 times (P < .001) and odds of death by 0.86 (P = .043).

CONCLUSIONS

High PB% detected by PAP machine data is a predictor of impending HF exacerbation and hospitalization. Improved PAP adherence and optimization of medical therapy may reduce hospitalization and all-cause mortality.

CITATION

Ullah MI, Tamanna S, Bhagat R. High nocturnal periodic breathing reported by PAP adherence data predicts decompensation of heart failure. J Clin Sleep Med. 2023;19(3):431-441.

Bidirectional association between chronic kidney disease and sleep apnea: a systematic review and meta-analysis

BACKGROUND

Previous data have suggested a link between chronic kidney disease (CKD) and sleep apnea (SA). However, the prevalence and risk association of both disease entities are not uniformly described.

METHODS

Ovid MEDLINE, EMBASE, and the Cochrane Library were searched for eligible publications that included patients aged ≥ 18 years diagnosed with CKD or SA. Included studies were divided into two cohorts: (1) a cohort of CKD or end-stage kidney disease (ESKD) patients reporting the prevalence of SA or odds ratio (OR) for SA (CKD cohort) and (2) a cohort of SA patients reporting the prevalence of CKD/ESKD or OR for CKD/ESKD (SA cohort).

RESULTS

CKD cohort: Of 16 studies (n = 340,587), the pooled estimated prevalence of SA among CKD/ESKD patients was 47.5% (95% CI 28.8-66.9). The pooled adjusted OR for SA among CKD/ESKD patients was 1.961 (95% CI 1.702-2.260). Male sex, history of diabetes, and lower BMI were associated with increased prevalence of SA. SA cohort: Of 12 studies (n = 3,103,074), the pooled prevalence of CKD/ESKD among patients with SA was 8.2% (95% CI 4.7-13.7), whereas the pooled adjusted OR for CKD/ESKD among patients with SA was 2.088 (95% CI 1.777-2.452). Increasing age, higher BMI, male sex, white race, and history of diabetes were associated with higher prevalence of CKD/ESKD.

CONCLUSION

There was a bidirectional association between CKD/ESKD and SA. Interventions aiming to prevent the progression of either CKD or SA are important.

Does Kidney Transplantation Affect Sleep and Fatigue in Patients With Kidney Disease?

Supplemental Digital Content is available in the text.

Sleep disorders and fatigue are highly prevalent in chronic kidney disease (CKD) and end-stage kidney disease (ESKD) patients but there is limited evidence on the effect of kidney transplant (KTx) on these.

Sleep disordered breathing and fibroblast growth factor 23 in the Hispanic Community Health Study/Study of Latinos

Preclinical data suggest that hypoxia stimulates fibroblast growth factor 23 (FGF23) transcription and cleavage in osteocytes, resulting in elevated circulating c-terminal (cFGF23) levels but normal intact FGF23 (iFGF23) levels. We conducted a case-control study within the Hispanic Community Health Study/Study of Latinos to investigate whether sleep disordered breathing, as a model of hypoxemia, is independently associated with elevated cFGF23 levels in the general population and with elevated cFGF23 and iFGF23 levels in patients with chronic kidney disease (CKD), in whom FGF23 cleavage may be impaired. Cases (n = 602) had severe sleep disordered breathing defined as an apnea/hypopnea index (AHI) of ≥30. Controls without severe sleep disordered breathing (n = 602) were matched for sex and CKD stage. The median AHI in the cases was 45.8 (IQR 35.5-62.5) compared to 2.6 (IQR 0.6-8.2) in the controls. Cases had higher cFGF23 levels than controls (66.2 RU/mL, IQR 52.8-98.4 vs. 61.2 RU/mL, IQR 49.5-80.1, p value <0.001). There were no differences in iFGF23 levels between cases and controls. In adjusted linear regression and multinomial regression analyses, body mass index attenuated the relationship between severe sleep disordered breathing and cFGF23 levels. No significant relationships were seen in analyses of severe sleep disordered breathing and iFGF23 levels or in analyses of iFGF23 and cFGF23 stratified by CKD status. Additional studies using other models of intermittent and chronic hypoxia are needed to confirm whether hypoxia stimulates FGF23 transcription in humans and to determine the impact on iFGF23 levels in CKD.

Obstructive Sleep Apnea Increases Sudden Cardiac Death in Incident Hemodialysis Patients

BACKGROUND

Mortality in end-stage renal disease (ESRD) occurs predominantly from cardiovascular disease (CVD) and sudden cardiac death (SCD). Obstructive sleep apnea (OSA) is characterized by periodic airflow limitation associated with sleep arousal and oxygen desaturation and is prevalent in patients with ESRD. Whether OSA increases the risk for SCD, cardiovascular and all-cause mortality among hemodialysis patients remains unknown.

METHODS

In a prospective cohort of 558 incident hemodialysis patients, we examined the association of OSA with all-cause mortality, cardiovascular mortality, and SCD using Cox proportional hazards models controlling for traditional CVD risk factors.

RESULTS

Sixty-six incident hemodialysis patients (12%) had OSA. Mean age (56 years) and percentage of males (56%) were identical in OSA and no-OSA groups. Fewer African Americans had OSA than non-African Americans (9 vs. 18%, respectively). Participants with OSA had higher body-mass index, Charlson comorbidity score, and left ventricular mass index and greater prevalence of diabetes and coronary artery disease. During 1,080 person-years of follow-up, 104 deaths occurred, 29% of which were cardiovascular. OSA was associated with a higher risk of all-cause mortality (HR 1.90 [95% CI 1.04-3.46]) and cardiovascular mortality (HR 3.62 [95% CI 1.36-9.66]) after adjusting for demographics and body-mass index. OSA was associated with a higher risk of SCD after adjusting for demographics (HR 3.28 [95% CI 1.12-9.57]) and multiple cardiovascular risk factors.

CONCLUSIONS

Incident hemodialysis patients with OSA are at increased risk of all-cause and cardiovascular mortality and SCD. Future studies should assess the impact of screening for OSA and OSA-targeted interventions on mortality in ESRD.

Effect of extended hours dialysis on sleep quality in a randomized trial

AIM

Poor sleep quality is common in haemodialysis patients and associated with worse outcomes. In this pre-specified analysis, we examined the impact of extended hours haemodialysis on sleep quality.

METHODS

The ACTIVE Dialysis trial randomized 200 participants to extended (≥24 h/week) or standard (target 12-15 h) hours haemodialysis over 12 months. Sleep quality was measured in the Kidney Disease Quality of Life Short Form 1.3 (KDQOL-SF) by overall sleep quality score (0-10, 10 = 'very good') and the sleep subscale (0-100, 100 = 'best possible sleep') every 3 months via blinded telephone interview. The average intervention effect was calculated by mixed linear regression adjusted by time point and baseline score. Factors predicting sleep quality were assessed by multivariate regression analysis.

RESULTS

Overall sleep quality score and sleep subscale at baseline were similar in both groups (5.9 [95%CI 5.4-6.4] vs. 6.3 [5.9-6.8]; 65.0 [60.9-69.1] vs. 63.2 [59.1-67.3]; extended and standard hours, respectively). Extended hours haemodialysis led to a non-significant improvement in overall sleep quality score (average intervention effect 0.44 (-0.01 to 0.89), P = 0.053) and sleep subscale (average intervention effect 3.58 (-0.02 to 7.18), P = 0.051). Poor sleep quality was associated with being female and with current smoking. Sleep quality was positively associated with EuroQol-5D (EQ5D) and the SF-36 Physical Component and Mental Component Summary Scores but not with hospitalizations.

CONCLUSION

Sleep quality was not significantly improved by extended hours dialysis in this study. Sleep quality is positively correlated with quality of life in haemodialysis patients and is poorer in women and current smokers.

Central Sleep Apnea in Patients with Congestive Heart Failure

Central sleep apnea and Cheyne-Stokes respiration are commonly observed breathing patterns during sleep in patients with congestive heart failure. Common risk factors are male gender, older age, presence of atrial fibrillation, and daytime hypocapnia. Proposed mechanisms include augmented peripheral and central chemoreceptor sensitivity, which increase ventilator instability during both wakefulness and sleep; diminished cerebrovascular reactivity and increased circulation time, which impair the normal buffering of Paco₂ and hydrogen ions and delay the detection of changes in Paco₂ during sleep; and rostral fluid shifts that predispose to hypocapnia.

Complementary roles of gasotransmitters CO and H2S in sleep apnea

Sleep apnea, which is the periodic cessation of breathing during sleep, is a major health problem affecting over 10 million people in the United States and is associated with several sequelae, including hypertension and stroke. Clinical studies suggest that abnormal carotid body (CB) activity may be a driver of sleep apnea. Because gaseous molecules are important determinants of CB activity, aberrations in their signaling could lead to sleep apnea. Here, we report that mice deficient in heme oxygenase-2 (HO-2), which generates the gaseous molecule carbon monoxide (CO), exhibit sleep apnea characterized by high apnea and hypopnea indices during rapid eye movement (REM) sleep. Similar high apnea and hypopnea indices were also noted in prehypertensive spontaneously hypertensive (SH) rats, which are known to exhibit CB hyperactivity. We identified the gaseous molecule hydrogen sulfide (H₂S) as the major effector molecule driving apneas. Genetic ablation of the H₂S-synthesizing enzyme cystathionine-γ-lyase (CSE) normalized breathing in HO-2^-/- mice. Pharmacologic inhibition of CSE with l-propargyl glycine prevented apneas in both HO-2^-/- mice and SH rats. These observations demonstrate that dysregulated CO and H₂S signaling in the CB leads to apneas and suggest that CSE inhibition may be a useful therapeutic intervention for preventing CB-driven sleep apnea.

Associations of common chronic non-communicable diseases and medical conditions with sleep-related problems in a population-based health examination study

A cross-sectional population-based survey, the National FINRISK 2012 Study, designed to monitor chronic diseases and their risk factors in Finland. A random sample of 10,000 adults aged 25-74 years, and of them, 64% (n=6424) participated the study. Participants subjectively reported the total durations for sleep and naps (n=6238), sleep quality (n=5878), bedtimes and wake-up times separately for working days and weekends yielding the amount of sleep debt (n=5878), and the seasonal variation in sleep duration (n=4852). The participants were asked whether they were diagnosed or treated for common chronic diseases in the past 12 months. Logistic regression models were adopted to analysis and adjusted for a range of covariates as potential confounding factors. Total sleep duration and nap duration prolonged in depression and other mental disorder (p<.001 for all). Seasonal variation in sleep duration was associated with depression (p=.014), hypertension (p=.018) and angina pectoris (p=.024). Participants with gallstones, cardiac insufficiency, depression, or degenerative arthritis had poor sleep quality (odds ratios of 1.6-6.3, p=.001 or less for each). Those with degenerative arthritis had sleep debt less (p<.05) and those with angina pectoris more (p<.05) than individuals without these medical conditions. Depression is significantly associated with sleep problems, albeit no sleep debt. Cardiovascular diseases, degenerative arthritis, and gallstones had significant associations with one or more sleep problems. There is therefore a need for more successful management of sleep problems in chronic diseases to improve the quality of life, to reduce treatment relapses, and to increase health and longevity in a population.

Role of adipocytes in hypertension

Although it has known for some time that obesity is associated with salt sensitivity and hypertension, recent data suggests that the adipocyte may actually be the proximate cause of this physiological changes. In the following review, the data demonstrating this association as well as the potentially operative pathophysiological mechanisms are reviewed and discussed.