Abstract | | |
Sleep apnea (SA) and excessive daytime sleepiness (EDS) are common sleep disorders among patients with end-stage renal disease (ESRD). This cross-sectional study, carried out in two dialysis centers in Saudi Arabia, assessed the prevalence of sleep apnea and sleepiness in Saudi patients with ESRD who are on maintenance dialysis with either peritoneal or hemodialysis. We used questionnaires to assess the prevalence of SA and EDS. The association between sleep apnea, EDS, and other sleep disorders, the underlying causes of renal failure, and other demographic data were also examined. Among 227 enrolled patients, the mean patient age was 55.7 years 17.2 years; 53.7% were male, and 46.3% were female. The overall prevalence of SA as defined by the Berlin questionnaire (BQ) was 37% in males and 34% in females, which was not a statistically significant difference (P = 0.459). Sleep apnea was significantly associated with age, neck size, afternoon and evening hemodialysis shift, obesity, diabetes, and hypertension (P-values, 0.001, 0.029, < 0.0001, < 0.0001, < 0.008, 0.002, and < 0.001, respectively). Sleep apnea was also significantly associated with other sleep disorders such as restless leg syndrome, insomnia, habitual snoring, and EDS (P-values, < 0.001, < 0.001, < 0.001, and < 0.001, respectively). The prevalence of EDS was 44%, and EDS was significantly more prevalent in patients undergoing peritoneal dialysis (P < 0.001); it was also associated with older age, diabetes mellitus, and other sleep disorders. SA and EDS are common in dialysis patients and are significantly associated with other sleep disorders.
How to cite this article: Al-Jahdali H. Prevalence of sleep apnea and excessive day time sleepiness in patients with end-stage renal disease on dialysis. Saudi J Kidney Dis Transpl 2012;23:251-61 |
How to cite this URL: Al-Jahdali H. Prevalence of sleep apnea and excessive day time sleepiness in patients with end-stage renal disease on dialysis. Saudi J Kidney Dis Transpl [serial online] 2012 [cited 2022 May 17];23:251-61. Available from: https://www.sjkdt.org/text.asp?2012/23/2/251/93146 |
Introduction | |  |
The prevalence of sleep disorders in chronic renal failure patients who are on dialysis is quite high; approximately 80% of such patients have sleep complaints. Unfortunately, little attention has been paid to the impact of these disorders on patients with end-stage renal disease (ESRD) who are on dialysis. [1],[2],[3],[4],[5] The prevalence of sleep apnea (SA) in ESRD and dialysis patients has been reported in (13-70%), [6] which is much higher than the general population (2-4%). [7],[8],[9],[10] This large variation in the prevalence of SA in dialysis patients is probably due to different populations being studied, the method of diagnosis [whether it is based on questionnaires or polysomnography (PSG)] and the definition used to diagnose SA. Excessive daytime sleepiness (EDS), a major consequence of SA, is caused by sleep fragmentation that is triggered by repetitive episodes of partial or complete upper airway obstruction. Sleep fragmentation may also contribute to impaired cognition and altered moods as well as subject the patient to increased risk of work- or driving-related accidents. [11],[12] Questionnaires based on symptoms are not sensitive or specific enough to identify patients with SA and may underestimate the true prevalence of SA. Nevertheless, sleep questionnaires are easy to administer, and subjective descriptions may still provide vital information for the diagnosis and management of sleep disturbances in dialysis patients. The Berlin questionnaire (BQ) has been validated as a good screening tool to identify patients at high risk for developing SA based on snoring behavior, daytime sleepiness or fatigue, and the presence of obesity or hypertension. [13] Patients may report insomnia or EDS. Insomnia is usually defined as difficulties initiating or maintaining sleep. [14] EDS is a physiological drive, defined as difficulty in maintaining an alert and awake state. [14] Both problems may impair quality of life in patients with ESRD and those on dialysis. In addition, insomnia and sleepiness are manifestations of other sleep disorders that include obstructive sleep apnea, restless leg syndrome (RLS) or periodic leg movement disorder (PLMD). Insomnia is reported in 50% of patients on hemodialysis, whereas subjective EDS have been reported in 52-67% of hemodialysis patients. [1],[2] RLS has been reported in 12-62% of dialysis patients, and PLMD was reported in approximately 14% of these patients. [15],[16],[17],[18],[19],[20] Any condition causing disturbed sleep due to respiratory events (apneas) or body movements (periodic leg movements) can cause frequent awakenings or brief arousals and may also increase daytime sleepiness, even if total sleep time is normal. Since its development in 1991, the Epworth sleepiness scale (ESS) has been commonly used in both clinical and research settings as a cost-effective method for assessing subjective day-time sleepiness. [21] It is an eight-item questionnaire that is designed to quantify a patient's sleep propensity by estimating the chance of dozing. Subjects rate each of the questions on a 0-3 scale, and the results are summed to produce a final score from 0 to 24. ESS scores less than 10 are considered normal, and scores greater than 10 suggest problems with excessive sleepiness. [21] The prevalence of "poor sleep" as estimated by Pittsburgh Sleep Quality Index (PSQI), (global score >5) has been reported to be 71% in dialysis patients. [22] The association of poor sleep quality with biochemical parameters is controversial; [22],[23] however, sleep quality is usually affected by the presence of other sleep disorders. The detection and management of sleep disorders in hemodialysis patients is often challenging. This study is designed to determine the sleep quality, the prevalence of SA (using BQ), and the prevalence of EDS in our patients with ESRD on maintenance dialysis and to delineate the associated clinical and biomedical parameters that may be linked to these sleep disorders. As we examine the prevalence of sleep apnea in our population, we will also summarize the prevalence of sleep apnea in most of the published studies.
Methods | |  |
This study was conducted as an observational cross-sectional study at King Abdulaziz Medical City - King Fahad National Guard Hospital (KAMC-KFNGH) - Riyadh and King Faisal Specialist Hospital and Research Centre (KFHRC) - Jeddah during the period from May 2007 to September 2007. This study was approved by the research and ethics committee at KAMC-KFNGH-Riyadh. All stable patients undergoing regular dialysis at both centers were enrolled in this study. We excluded confused or demented patients and those patients who refused to participate. The data collection was carried out by a professional personal interviewer, using a structured questionnaire. These questionnaires were adapted from standard international questionnaires and are used routinely at our sleep disorders center. All questionnaires were translated from English to Arabic and back translated from Arabic to English language by a professional medical translator. Moreover, these questionnaires were also reviewed by two sleep specialists for accuracy and the clarity of the Arabic translation. Finally, these questionnaires were pretested on 30 patients and then modified for any ambiguity or vagueness.
Data collected included common demographic characteristics such as age, gender, education level, marital status, employment, and personal habits. Data regarding past medical history, medication, underlying cause of chronic renal failure, duration of the dialysis and the dialysis shift were also collected.
The ESS was used to measure daytime sleepiness, with a score of more than 10 indicating increased sleepiness. [21] BQ was used to assess the risk of SA. The BQ was developed in 1996, and its validity and accuracy in primary care settings has been previously shown. [13] The details of the questionnaire have been published previously. [13] However, in brief, the questionnaire is divided into three sections. Section 1 addresses snoring and witnessed apnea. Those patients who snore are asked to rate their snoring with regard to loudness, frequency, and whether their snoring bothers other people. Section 2 addresses daytime fatigue and sleepiness. Section 3 addresses personal history of hypertension, as well as height, weight, and gender. Then, the body mass index (BMI) is calculated.
Three categories in BQ are defined based on the information collected. In category 1, a positive response is defined as frequent symptoms (>3 times per week) in the questions about snoring and witnessed apneas. In category 2, a positive response is defined as frequent symptoms in two or more questions about fatigue, sleepiness, and/or drowsy driving. In category 3, a positive response is defined as a self-report of hypertension and/or a BMI >30 kg/m [2] . Based on the data collected, patients are stratified into high risk for SA and low risk for SA according to their responses. Individuals who have positive scores in at least two of the three categories are scored as high risk for SA. Individuals who do not meet the above criteria are scored as low risk for SA. The high-risk pretest probability for SA has been previously found to predict a respiratory disturbance risk expressed as a respiratory disturbance index (RDI) of >5 with a sensitivity of 86% and a specificity of 77%. [13] The Pittsburgh Sleep Quality Index (PSQI) was also used to assess sleep quality. In this questionnaire, the details of which have been published previously, a score of 5 or more indicates poor sleep quality. [24] We also used the ICSD-2 definition for insomnia: difficulty in falling asleep or waking up too early, frequent awakening with difficulty falling asleep again, and secondary daytime impairment related to nighttime sleep difficulties. [25] The diagnosis of RLS is clinical, and its definition has been clarified and standardized by internationally recognized diagnostic criteria, published by the International Restless Legs Syndrome Study Group (IRLSSG) which we used in our study. [26] Data were summarized as either mean and standard deviation or number and percent, as appropriate. To assess the possible influence of demographic and other variables on the prevalence of SA and EDS, we used the unpaired t-test and the Mann-Whitney U-test for nonparametric data, as appropriate. A multivariate logistic regression analysis was used to assess the risk of EDS (defined by an ESS score >10) and the risk of SA (defined by the BQ as high risk or low risk categories) while controlling for other sleep disorders, such as RLS and an elevated PSQI score (greater than 5, indicating poor sleep quality). A P-value of less than 0.05 was considered statistically significant. Data management and analyses were carried out using the Statistical Package for Social Sciences (SPSS), version 13.
Results | |  |
A total of 227 patients were recruited for the study with mean age of 55.7 ± 17.2 years. There were 122 males (53.7%) and 105 females (46.3%). The mean duration on dialysis was 40.4 ± 37.8 months. Diabetes mellitus was the most common cause of renal failure (52%). A majority of patients (80%) had less than a high school education, and 50.7% were employed. Among these patients, nonsmokers were a majority as well (77%). Daily and regular coffee intake was reported in 75.8%. The most common medications used were erythropoietin and iron supplements (96.5%), vitamins (91.6%), antihypertensive medications (84%), and antidepressants (8.8%). Other patient characteristics are shown in [Table 1]. The overall prevalence of SA as defined by the BQ was 37% in males and 34% in females, which was not a statistically significant difference (P = 0.459). Age was a significant risk factor for SA (P = 0.001), with older patients at higher risk than young. Risk of SA was significantly higher in peritoneal dialysis patients than in hemodialysis patients (P = 0.001) and also more in the morning shift patients compared to afternoon or evening shift (P < 0.001). Obesity was also significantly associated with increased the risk for SA (P = 0.028). There were also significant associations of higher risk for SA with DM (P = 0.002) and hypertension (P = 0.001). Smoking and coffee intake were not associated with a significantly increased risk for obstructive sleep apnea (P = 0.31 and P = 0.735, respectively). There was no significant association between higher risk for SA and dialysis efficacy as measured by KT/V, as shown in [Table 2], or between higher risk and other biochemical parameters, such as hemoglobin, urea, creatinine, calcium, and phosphorus (data not shown). Patients who were at higher risk for SA had significantly greater symptoms of insomnia, RLS, habitual snoring, and excessive daytime sleepiness (all P-values <0.001), as shown in [Table 3]. EDS, as measured by an ESS score greater than 10, was also associated with a higher risk of SA, snoring, and RLS, as shown in [Table 4]. Almost all of the patients, 224 (99%), had poor sleep quality. The reported prevalence of SA in previous studies, including our study, is summarized in [Table 5]. | Table 2. Association between OSAS and other characteristics (patient characteristics, shift and type of dialysis, lifestyle habits, and underlying medical problems).
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 | Table 4. Association between EDS (ESS ≥10) and other characteristics (patient characteristics, shift and type of dialysis, lifestyle habits, and underlying medical problems).
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 | Table 5. Reported prevalence of sleep apnea in previous studies, including the current study.
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Discussion | |  |
Sleep disorders are common in dialysis patients. [2],[5],[6],[7],[27],[28],[29] SA is common and causes significant comorbidities in patients with end-stage renal disease who are on dialysis; the reported prevalence ranges from 20% to 90% [Table 5]. The major reasons for this variation in prevalence are the method of the diagnosis selected (questionnaire or overnight polysomnography) and the definition used to diagnose SA. The reported prevalences for SA are much higher than those for the general population (2-4%). [30] However in our study, the prevalence of SA as defined by the BQ was 37% in males and 34% in females, which is not a statistically significant difference. If we compare the prevalence of SA in dialysis patients to the prevalence of SA in the general Saudi population, it is not significantly different. Using the same BQ, the prevalence of SA was 39% in females and 33.3% in males. [31],[32] We believe that this is a major strength of our study: we used the same questionnaires in both the normal population and the dialysis patients, and we found no significant differences in prevalence. Similar to other reported studies, there was a significant association between higher risk for SA and older age, neck size, dialysis shift, hypertension, DM, and obesity. [12],[33],[34],[35],[36],[37] However, some other reported studies did not find any such associations. [28],[38],[39],[40],[41]
In our study, the BMI was 26.7 ± 6.4, which is a much higher than the BMI in the studies that reported a lower prevalence of SA [2],[6],[35] but similar to other studies with a moderate to high prevalence of SA. [9],[34],[42] Previous studies have reported almost equal prevalence of sleep apnea in patients undergoing both hemodialysis and peritoneal dialysis. [43],[44] In our study we sleep disorders was significantly less common in patients undergoing hemodialysis.
Excessive daytime sleepiness was significantly associated with a higher risk of SA. Although such an association has been reported before, [4],[28] others have questioned it. [4] Furthermore, SA is not the only cause of EDS in dialysis patients; it may be caused by associated medical problems, insomnia or RLS, [6],[9],[12] which were significantly associated with SA in our study as well. Hui et al [35] reported no association between EDS and age, SA, RLS, and habitual snoring. However, others have reported such associations. [6],[12] In our study, EDS as measured by the ESS was reported by 43% of the patients in general, 94% of patients at high risk for SA, 56% of habitual snorers, and 71% of those patients with RLS. There are a few weak points of this study. One is the fact that this is an observational rather than a prospective study, with the known limitations of observational studies. Another is the stratification for high risk of SA based on the BQ without confirmation by PSG. However, the BQ has high pretest probability for SA; it was found previously to predict an RDI of >5 with a sensitivity of 86%, a specificity of 77%, a positive predictive value of 89% and a likelihood ratio for SA of 3.79, [13] The other weak point that may be noted is the fact that the questionnaires were not validated; however, in this study we did not devise any of our own instrument for assessment of sleep disorders but, used questionnaires that was validated in the general population. We believe that there was no component in any of the questionnaires that might make them inapplicable to our patients. In addition, this survey was conducted by a professional interviewer. Furthermore as explained in the methodology section, these questionnaires were translated from English to Arabic and back-translated to English by a professional translator, verified by sleep specialists, tested for clarity in a pilot study and then used in the sleep lab questionnaires and two published studies. [31],[32] Strength of our study is that it is the first study in the Saudi population addressing sleep disorders in dialysis patients, and it may help health care providers become more aware of common sleep disorders in their patients. This increased awareness is important because studies have shown that sleep disorders in dialysis patients lead to poor life quality and increase morbidity and mortality. [23],[45],[46],[47] SA and EDS are common in hemodialysis patients and are significantly associated with other sleep disorders. While taking care of dialysis patients, greater attention needs to be given to the diagnosis and management of SA and other causes associated with EDS.
Acknowledgement | |  |
I would like to thank Dr. Abdullah Al-Sayarri, Dr. Fayz Al-Hejali and Dr. Said Al-Gamedi for their help to arrange the interview with the patients, provide me with pertinent laboratory result, to thank Dr. Waleid AlQadi, and Dr. Hithm Khogair for their support. Also thank Dr. Hani Tamimi for reviewing all statistics and data analysis and all dialysis staff in both hospitals. Special thanks for King Abdullah International Research centre for funding and supporting this study and editing the manuscript.[57]
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Correspondence Address: Hamdan Al-Jahdali Associate Professor, Head of Pulmonary Division, Medical Director of Sleep Disorders Centre, King Saud University for Health Sciences, King Abdulaziz Medical City, Riyadh Saudi Arabia
 Source of Support: None, Conflict of Interest: None  | Check |
PMID: 22382215  
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5] |