currently , chronic kidney disease ( ckd ) is one of the most serious public health problems . 

some recent epidemiological studies have suggested that approximately one million people 
 with end stage renal disease ( esrd ) undergo replacement therapy worldwide .
the increased 
 prevalence of ckd in the developed and developing countries threatens to become a global 
 epidemic , as exemplified by the increased number of cases of diabetes mellitus and the 
 increased life expectancy of the population1 .
ckd severely affects patients health , lifestyle and wellbeing , 
 compromising their quality of life2 . 
 according ponngeon et al .
, ckd patients had  sedentary  and  inactive  levels of physical 
 activity on dialysis and non - dialysis days , respectively3 .
silva and marinho observed that the level of physical activity of 
 most patients esrd undergoing hemodialysis is poor and that most do not perform exercise 
 regularly4 .
the most common 
 comorbidities observed in patients with ckd are diabetes mellitus type 2 , 
 dyslipidemia , coronary heart disease , heart failure5 , 
 6 , hypertension7 , 8 , respiratory 
 disorders8 , 9 , stress10 , 
 depression10,11,12 , anxiety13 , and obstructive sleep apnea ( osa)14 .
osa is a major medical problem , estimated to affect up to 1530% of male adults and up to 
 515% of female adults15 , 16 .
it is characterized by repetitive obstructions of the 
 upper airway during sleep , frequently causing oxygen desaturation .
this induces frequent 
 awakenings ( arousals ) , resulting in fragmented sleep and excessive daytime sleepiness . in brazil , according to a recent epidemiological study conducted in so paulo , an osa 
 prevalence of 24.8% in men and 9.6% in women was observed , based on an apnea - hypopnea index 
 ( ahi)15 events / h ; for an ahi5 events / h , this prevalence increased to 40% in men and 26% in 
 women17 . in a recent study involving 
 2,121 individuals conducted in the city of lausanne in switzerland , a prevalence of 50% in 
 men and 23% in women
was observed , based on an ahi15 events / h18 . in another study conducted by oliveira et al .
, patients 
 with neuromuscular disorders such as myasthenia gravis were observed to have a poor quality 
 of sleep , excessive daytime sleepiness , presence of restless syndrome , and a high incidence 
 of sleep - disordered breathing ( sdb)19 .
the prevalence of sleep disorders among patients with ckd is 4080% , which is higher than 
 that among the general population . among these sleep disorders ,
the presence of periodic leg 
 movements during sleep and osa has been highlighted20 . the high prevalence ( 50% ) of sdb in patients undergoing hemodialysis ( hd ) can be attributed 
 to compromised upper airway stability ( extracellular fluid volume overload)21,22,23 , ventilatory control instability ( altered 
 central and peripheral chemosensitivity ) , and reduced upper airway muscle tone ( uremia)24,25,26,27,28
. risk factors of sdb in the general 
 population , such as older age , male gender , obesity , smoking , increased neck circumference , 
 and diabetes , are also prevalent in the ckd population29 .
sdb has been associated with increased cardiovascular risk , and may contribute to the 
 morbidity and mortality of patients with advanced ( stages 4 to 5 ) ckd or those undergoing 
 hd30 .
although numerous studies have shown that a substantial proportion of patients undergoing 
 hd have sleep apnea , these studies were limited by the following factors : very small sample 
 sizes27 , 31,32,33,34 ; the use of partial 
 channel polysomnography ( psg)34,35,36 ; the study of 
 populations with limited generalizability to patients undergoing hd37 ; a selected subpopulation of patients undergoing dialysis , 
 without sleep symptoms38 ; or study 
 samples that were largely composed of symptomatic patients26 , 31 , 39 . hence , a better understanding of the prevalence and risk factors 
 of sdb in ckd patients undergoing hd is critical .
therefore , a systematic review that can 
 demonstrate the status of the knowledge is justified .
this knowledge may enable health 
 professionals , especially physiotherapists , to devise new strategies to reduce morbidity and 
 mortality and improve the quality of life of ckd patients . the present study aimed to 
 provide a thorough overview of the literature regarding the occurrence of sleep disorders in 
 patients with esrd undergoing hd .
two independent reviewers performed a computer - assisted search of the medline , lilacs , and 
 scielo virtual health library medical databases from their inception to november 2015 .
a 
 combination of the following medical subject headings ( mesh ) were used in the search 
 (  sleep  or  sleep disorders  or  obstructive sleep apnea  ) and (  kidney dialysis  or 
  hemodialysis  or  dialysis  ) .
the first stage of the search identified articles according to the title , abstract , and key 
 words . in the second stage ,
articles that 
 involved patients > 18  years old , having esrd and undergoing hd , and that used overnight 
 standard psg for the diagnosis of sleep disorders , were included in the final analysis .
one thousand one hundred twenty - six articles were identified that met the inclusion 
 criteria .
a total of 796 articles were excluded because they were not in english , the 
 patients did not undergo hd , or the studies were not cross - sectional or clinical trials . 

after an evaluation of the full text , 312 studies were excluded , either because psg was not 
 performed or they were duplicated .
the remaining 18 studies , comprising 8 clinical trials 
 and 10 cross - sectional studies , were included for further examination ( fig . 1fig .
the results and outcomes of all included studies are summarized in tables 1table 1.cross-sectional studies that used overnight standard polysomnography for the 
 diagnosis of sleep disorders in chronic kidney diseaseauthor .
200136improvement of sleep apnea in patients with chronic renal failure 
 who undergo nocturnal hemodialysispatients who underwent both conventional hd and nocturnal hd 
 ( n=14)ahi decreased during the nocturnal hd phase.nocturnal hd corrects sa associated with chronic renal 
 failure.sanner et al .
200230sleep - related breathing disorders impair quality of life in 
 hemodialysis patientsesrd patients who underwent hd ( n=46)twenty - one patients had clinically significant sleep - related 
 breathing disorders with a median ahi of 13.3 events / h.twenty - seven ( 22.7% ) of the 119 patients had sa with subjective 
 symptoms such as daytime somnolence and snoring.parker et al .
200337daytime sleepiness in stable hemodialysis patientsesrd patients who underwent hd ( n=46)higher indices of sa and brief arousals correlated significantly 
 with increased physiological , but not subjective , sleepiness.daytime sleepiness is common in hd patients , and may be severe 
 despite the absence of obvious clinical risk factors.parker et al .
200333nocturnal sleep , daytime sleepiness , and quality of life in stable 
 patients on hemodialysisesrd patients who underwent hd ( n=46)better sleep quality and less daytime sleepiness were associated 
 with improved qol in stable hd subjects.poor nocturnal sleep and increased daytime sleepiness are 
 associated with decreased qol in hd patients.jung et al .
200532sleep apnea , coronary artery disease , and antioxidant status in 
 hemodialysis patientsesrd patients who underwent hd ( n=26)coronary artery calcification is associated with the severity of 
 sa.oxygen desaturation triggered by sa is associated with severe 
 coronary artery disease.miskowiec et al .
200638prevalence of sleep apnea syndrome in hemodialyzed patients with 
 end stage renal diseaseesrd patients , assessed using psg , on the night before hd ( n=17 ) 
 and on the night after hd ( n=11)seven patients presented with sa on the 2 nights during the 
 psg.hd does not change the prevalence of osa in ckd.tada et al .
200739the predictors of central and obstructive sleep apnoea in 
 haemodialysis patientsesrd patients who underwent hd ( n=30)forty - one patients presented with sa ; 27 had sa with symptoms such 
 as daytime somnolence and snoring.there is a high prevalence of sa in hd patients .
201016nocturnal hypoxemia and periodic limb movement predict mortality in 
 patients on maintenance hemodialysisesrd patients who underwent hd ( n=30)the median ahi and the plm index were 22 and 36.9 events / h , 
 respectively.nocturnal hypoxemia and periodic limb movement during sleep were 
 associated with an increased risk of death in patients with esrd.elias et al .
201240rostral overnight fluid shift in esrd renal disease : relationship 
 with obstructive sleep apneaesrd patients who underwent hd ( n=26)the change in the leg fluid volume was correlated with the 
 apnea  hypopnea time and neck circumference.nocturnal rostral fluid shift is associated with the severity of 
 osa in esrd.elias et al .
201341relationship of pharyngeal water content and jugular volume with 
 severity of obstructive sleep apnea in renal failureesrd patients who underwent hd ( n=20)a positive correlation was found among the ahi , the internal 
 jugular vein volume , and the upper airway mucosal water content.fluid overload increases the internal jugular vein volume and the 
 upper airway mucosal water content , contributing to the pathogenesis of osa in 
 esrd patients.ahi : apnea - hypopnea index ; hd : hemodialysis ; esrd : end stage renal disease ; sa : sleep 
 apnea ; qol : quality of life ; osa : obstructive sleep apnea ; ckd : chronic kidney 
 disease ; plm : periodic leg movementand 2table 2.clinical trials that used overnight standard polysomnography for the diagnosis of 
 sleep disorders in chronic kidney diseaseauthor .
200542polysomnographic measures of nocturnal sleep in patients on 
 chronic , intermittent daytime hemodialysis vs those with chronic kidney 
 diseaseesrd patients who underwent hd ( n=16 ) and the ckd patients 
 ( n=8)both groups had reduced total sleep time and sleep efficiency.sleep disorders of ckd patients and those receiving chronic , 
 intermittent daytime hd may have different etiologies.lee et al .
200643a secondary analysis of racial differences in periodic leg 
 movements in sleep and ferritin in hemodialysis patientsesrd african  american patients who underwent hd ( n=36 ) ; esrd 
 caucasian patients who underwent hd ( n=10)african  american hd patients had higher ferritin and lower plm than 
 caucasians.plm was less common in the african  american population , suggesting 
 a differential genetic vulnerability.unruh et al .
200644sleep apnea in patients on conventional thrice - weekly hemodialysis : 
 comparison with matched controls from the sleep heart health studyesrd patients who underwent hd ( n=46 ) and the normal renal function 
 group ( n=137)esrd patients had a higher frequency of arousals per hour and ahi , 
 and greater percentage of the tst below an oxygen saturation of 90%.there was a strong association of hd with severe sdb and nocturnal 
 hypoxemia independent of age , bmi , and a higher prevalence of chronic 
 disease.beecroft et al .
200711pharyngeal narrowing in end - stage renal disease : implications for 
 obstructive sleep apnoeaesrd patients who underwent hd ( n=44 ) and the normal renal function 
 group ( n=41)the pharynx was narrower in patients who underwent hd than in 
 subjects with normal renal function.a narrower upper airway can contribute to the pathogenesis of sleep 
 apnea in dialysis - dependent patients.unruh et al .
200845subjective and objective sleep quality in patients on conventional 
 thrice - weekly hemodialysis : comparison with matched controls from the sleep heart 
 health studyesrd patients who underwent hd ( n=46 ) and the normal renal function 
 group ( n=137)there was no association between psg sleep time and self - reported 
 sleep time or between the ess and the severity of sa in the hd population.kidney failure treated with thrice - weekly hd is significantly 
 associated with poor subjective and objective sleep quality.enomoto et al .
200846clinical characteristics of restless legs syndrome in end - stage 
 renal failure and idiopathic rls patientsuremic rls patients ( n=15 ) and idiopathic rls patients ( n=20)the plm index was significantly higher in the uremic rls 
 group.uremic rls appears to deteriorate faster and to become more severe 
 than idiopathic rls.loewen et al .
200947sleep disruption in patients with sleep apnea and end - stage renal 
 diseaseesrd patients who underwent hd ( n=12 ) and a normal renal function 
 group ( n=18)the prevalence of rls lm - related arousals was higher in esrd 
 patients.the co - existence of plm is an additional source of sleep disruption 
 in patients with esrd and sa.roumelioti et al .
201148sleep - disordered breathing and excessive daytime sleepiness in 
 chronic kidney disease and hemodialysisesrd patients who underwent hd ( n=75 ) , the ckd group ( n=89 ) , and 
 the normal renal function group ( n=224)nocturnal hypoxemia was significantly elevated in the hd group 
 compared with the ckd group.severe sdb and excessive daytime sleepiness are common among 
 advanced ckd and hd patients.esrd : end - stage renal disease ; hd : hemodialysis ; ckd : chronic kidney disease ; plm : 
 periodic leg movement ; sdb : sleep disordered breathing ; psg : overnight standard 
 polysomnography ; ess : epworth sleepiness scale ; sa : sleep apnea ; rls : restless legs 
 syndrome ; tst : total sleep time and are discussed below .
thus , a detailed analysis of 18 articles that used 
 overnight psg , which is considered the gold standard method for the diagnosis of sleep 
 disorders , was conducted .
flowchart of the study ahi : apnea - hypopnea index ; hd : hemodialysis ; esrd : end stage renal disease ; sa : sleep 
 apnea ; qol : quality of life ; osa : obstructive sleep apnea ; ckd : chronic kidney 
 disease ; plm : periodic leg movement esrd : end - stage renal disease ; hd : hemodialysis ; ckd : chronic kidney disease ; plm : 
 periodic leg movement ; sdb : sleep disordered breathing ; psg : overnight standard 
 polysomnography ; ess : epworth sleepiness scale ; sa : sleep apnea ; rls : restless legs 
 syndrome ; tst : total sleep time
the aim of this study was to conduct a systematic review of studies showing the presence of 
 sleep disorders in patients with esrd undergoing hd .
the presence of sleep disorders , including sdb , periodic limb movement disorder ( plmd ) 
 and/or restless legs syndrome ( rls ) , which compromise the quality of life and increase the 
 morbidity and mortality rates of patients with ckd , has been documented in the 
 literature50,51,52,53 .
seventy percent of esrd patients are believed to have some form of 
 sdb26 , 39 .
rls is a common and extremely distressing problem experienced by 
 many patients undergoing hd .
it is a neurological condition characterized by an irresistible 
 urge to move the legs and occurs more frequently during inactivity and at night54 , 55 .
the prevalence of rls in patients who are under treatment with hd 
 varies across studies performed in broad geographical regions ( 6.668% ) , and recent studies 
 using the international rls study group criteria have suggested a prevalence rate of 33% in 
 esrd patients , which is greater than that in the general population56 .
sleep fragmentation and sleep deprivation caused by rls may contribute to cardiovascular 
 complications and infections , often with poor prognosis in patients undergoing hd . according 
 to the literature ,
patients undergoing hd have a poorer quality of sleep compared to the 
 normal population .
the presence of rls and associated sleep disorders , such as daytime 
 sleepiness , insomnia , and poor sleep quality , should be considered a problem that further 
 impairs the quality of life of patients .
studies have demonstrated that 4080% of esrd 
 patients undergoing hd suffer from poor sleep quality associated with a poor quality of 
 life57 , 58 .
sleep disorders are usually associated with physical , behavioral , 
 and psychological disorders that predispose to cognitive impairment , decline in social 
 performance and interpersonal interactions , and depression59 .
sdb is very common among patients with ckd , especially those undergoing hd36 , 60 .
some studies have suggested osa has a prevalence of 5060% in esrd 
 patients12 , 61 .
depending on the methodology applied , approximately 5080% of ckd 
 patients have some form of sdb26 , 39 .
osa is 4 to 10 times more prevalent among 
 ckd patients than in the general population22 , 49 .
a more recent study conducted by nicholls 
 et al . involving 254 ckd patients showed a significant increase in the occurrence of sdb 
 ( predominantly osa ) which was related to impairment of renal function , with a prevalence of 
 57%62 .
this study utilized only studies performed using psg , considered the gold standard for the 
 diagnosis of sleep disorders . despite the high prevalence of sleep disorders in the ckd 
 population , there is limited scientific research on the topic , as evidenced by only as shown 
 by 18 studies ( 10 cross - sectional studies and 8 controlled clinical trials ) having been 
 retrieved in this review .
this is perhaps explained by the high cost of psg examination , or 
 by a lack of knowledge about the presence of sleep disorders in ckd population .
other more viable diagnostic methods , such as pulse oximetry and specific validated sleep 
 questionnaires , could be used as screening tools for the presence of sdb , aiding in the 
 early diagnosis and choice of appropriate treatment with non - invasive ventilatory 
 support .
esrd contributes to the emergence and/or development of osa due to factors such as metabolic 
 acidosis , compromised sensitivity of chemoreceptors , uremic toxins , generalized muscle 
 weakness , particularly of the dilator muscles of the pharynx , and narrowing of the upper 
 airway due to fluid accumulation in the interdialytic period .
it is known that osa induces 
 ckd due to increased blood pressure , oxidative stress , and repetitive hypoxia .
this systematic review verified the status of knowledge regarding the prevalence of sleep 
 disorders in esrd patients undergoing hd . according to the studies analyzed ,
a high 
 prevalence of plmd , rls , and osa affecting the quality of sleep was observed , which in turn 
 undermined the quality of life of these patients , leading to increased morbidity and 
 mortality .
thus , it is very important for healthcare professionals to recognize the signs and symptoms 
 of sleep disorders in ckd patient population , both for accurate diagnosis and an appropriate 
 therapeutic approach . for physical therapists ,
it is extremely important to identify sdb , 
 particularly osa , so they can institute treatment with continuous positive airway 
 pressure .
 the purpose of this study was to conduct a systematic review of the available evidence on 
 sleep disorders in patients with end stage renal disease ( esrd ) undergoing hemodialysis 
 ( hd ) . 
 [ subjects and methods ] two independent reviewers performed a computer - assisted 
 search of the medline , scielo , lilacs , and bireme virtual health library medical databases 
 from their inception to november 2015 . 
 [ results ] one thousand one hundred twenty - six 
 articles were found that met the inclusion criteria . 
 articles were excluded if they were 
 not in english , the patients did not undergo hd , or the studies were not cross - sectional 
 or clinical trials . 
 after reading the full text , a further 300 studies were excluded 
 because they did not use polysomnography . 
 the remaining 18 studies with esrd patients 
 undergoing hd comprised 8 clinical trials and 10 cross - sectional studies . 
 this systematic 
 review followed the criteria outlined by the prisma declaration . 
 [ conclusion ] in this 
 systematic review , a high prevalence of sleep disorders was observed in esrd , including 
 sleep - disordered breathing . 
 this knowledge may enable health professionals to devise new 
 strategies for the diagnosis and treatment of these patients , in order to reduce morbidity 
 and mortality and improve their quality of life . 
INTRODUCTION
SUBJECTS AND METHODS
RESULTS
DISCUSSION