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Nephrol Dial Transplant (2016) 31: 772–779 doi: 10.1093/ndt/gfv306 Advance Access publication 26 August 2015
ORIGINAL ARTICLE
Proteinuria is associated with sleep apnea in chronic kidney disease Gary C.W. Chan1, Bing Lam2, Desmond Y.H. Yap1, Mary S.M. Ip2, Kar Neng Lai3 and Sydney C.W. Tang1 1
Division of Nephrology, Department of Medicine, University of Hong Kong, Queen Mary Hospital, Pok Fu Lam, Hong Kong, 2Division of
Respiratory and Sleep Medicine, Department of Medicine, University of Hong Kong, Queen Mary Hospital, Pok Fu Lam, Hong Kong and 3
Nephrology Center, Hong Kong Sanatorium and Hospital, Happy Valley, Hong Kong
Correspondence and offprint requests to: Sydney C.W. Tang; E-mail:
[email protected] and proteinuria were 1.23 (95% CI 1.05, 1.45; P ≤ 0.05) and 1.75 (95% CI 1.12, 2.76; P ≤ 0.05). However, no significant correlation between the prevalence and severity of SA and NH with progressive renal deterioration was observed. Furthermore, no significant mean difference in the apnea–hypopnea index and ODI was observed for an ESS above and below 10. Conclusions. SA is prevalent in CKD patients and strongly correlated with BMI and proteinuria, but not with renal function. The ESS is an investigative tool that lacks discriminatory power in patients with renal insufficiency. Therefore clinical vigilance for SA is paramount when attending to CKD patients with significant proteinuria.
A B S T R AC T Background. The prevalence and severity of sleep apnea (SA) in the chronic kidney disease (CKD) population is not well characterized. Recent studies have yielded highly variable prevalence rates due to cohort heterogeneity and interstudy inconsistencies in defining SA. This study sought to determine the association of SA with CKD by recruiting a uniform cohort to undertake overnight polysomnography (PSG). Methods. A total of 141 male Chinese CKD patients, ages 40– 60 years, underwent overnight PSG to delineate the prevalence and severity of SA and nocturnal hypoxemia (NH). Body mass index (BMI), neck girth, estimated glomerular filtration rate, urinary protein excretion and Epworth sleepiness scale (ESS) score were collected at baseline to determine associative factors. Results. The prevalence rates of SA and NH were 35.5 and 10.6%, respectively, in this study population [mean (±SD) age 51.44 ± 6.05 years; BMI 26.05 ± 4.22 kg/m2]. The adjusted odds ratios (ORs) for SA by BMI and proteinuria were 1.18 [95% confidence interval (CI) 1.02, 1.37; P ≤ 0.05] and 1.57 (95% CI 1.12, 2.46; P ≤ 0.05), respectively. The adjusted ORs for the median cohort oxygen desaturation index (ODI) by BMI © The Author 2015. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.
Keywords: chronic kidney disease, proteinuria, sleep apnea
INTRODUCTION Sleep apnea (SA) has emerged as a major health problem with social and economic implications in our resource-restricted healthcare system [1]. Affecting up to 6% of the general population [2–4], it is characterized by intermittent nocturnal hypoxemia (NH) with subsequent sleep disturbance and 772
M AT E R I A L S A N D M E T H O D S Patient selection and recruitment Male patients, ages 40–60 years, attending outpatient nephrology clinics at Queen Mary Hospital and Tung Wah Hospital were recruited into this study. Patients with acute kidney injury from any cause, active acute medical complications, such as congestive heart failure and chronic obstructive pulmonary disease exacerbation, were excluded. All patients receiving corticosteroid therapy or medications for nocturnal sedation were also excluded. CKD classification Patients were stratified based on their estimated glomerular filtration rate (GFR) at enrollment into five discrete CKD stages as per the National Kidney Foundation CKD classification [34]. Estimated GFR was calculated using the four-variable Modification of Diet in Renal Disease formula. This study was approved by the local institutional review board and complies with the Declaration of Helsinki. Informed consent was obtained from all study participants.
Proteinuria, sleep apnea and CKD
Data collection The baseline data collection for all enrolled patients included age, height, weight, neck circumference and Epworth sleepiness scale (ESS) questionnaire score. Serum creatinine, estimated GFR and spot urinary protein excretion within 2 months of PSG assessment were collected from electronic patient records. Assessment of sleep-disordered breathing A full sleep assessment was performed for each patient using overnight PSG, the gold standard diagnostic tool in detecting sleep disorders. The Alice 5 PSG machine recordings included electroencephalogram, electrooculogram, submental electromyogram (EMG), bilateral anterior tibial EMG, electrocardiogram, chest and abdominal wall movement by inductance plethysmography, respiratory airflow by nasal pressure transducer and finger pulse oximetry. All variables were continuously recorded by a computerized data acquisition system. Subsequently, recordings were analyzed by an automated scoring system in accordance with standardized criteria in an offline procedure. Definitions and criteria Apneas are defined as cessation, or near cessation, of airflow for ≥10 s. Hypopneas are defined as airflow reductions of ≥30% from baseline for at least 10 s and accompanied by ≥3% oxygen desaturation [35]. These definitions are continuously updated and validated by the American Academy of Sleep Medicine. The average total number of apneas and hypopneas per hour of sleep constitutes the AHI. Arbitrarily, a stand-alone AHI ≥15 signifies SA [36], whereas an index ≥30 represents severe SA. NH as a result of apnea and hypopnea is defined by oxygen desaturations to
