Original article

I. MISKOWIEC1, J.J. KLAWE1, M. TAFIL-KLAWE2, K. JESKE1,
A. LAUDENCKA1, B. BIELICKA1, J. MANITIUS3, P. ZLOMANCZUK4


PREVALENCE OF SLEEP APNEA SYNDROME IN HEMODIALYZED
PATIENTS WITH END-STAGE RENAL DISEASE


1Department of Hygiene and Epidemiology, 2Department of Physiology, 3Department of Nephrology, Hypertension and Internal Medicine,
4Department of Neuroimmunology, Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University in Torun, Poland.


  The majority of hemodialyzed patients suffer from sleep disturbances. In the present study the prelevence of sleep apnea syndrome in hemodialyzed patients with end-stage renal disease (ESRD-patients) was investigated by the survey, Epworth Sleepiness Scale (ESS), and polysomnography (PSG). Sixty-one patients: 24 women and 37 men were involved in the study. All subjects participated in the first part of the study consisting of the survey and ESS. The second and third parts consisted of nighttime PSG, performed the night after hemodialysis (17 patients) and between hemodialyses (11 patients). Eleven out of the 61 patients had the symptoms of sleep apnea and heavy daily sleepiness. Eleven subjects were involved in the double PSG study: after and between hemodialyses. Obstrucive sleep apnea was found in 7 of those patients during both nights analyzed. Our results confirm the occurrence of sleep disorders in ESRD-patients. Hemodialysis does not change the prevalence of obstructive sleep apnea in chronic renal disease.

Key words: apnea-hypopnea, breathing disturbances, daily sleepiness, end- stage renal diseases, hemodialyzed patients, obstructive sleep apnea



INTRODUCTION

Studies concerning sleep problems in hemodialyzed patients clearly demonstrate that sleep disturbance is a common feature of end-stage renal disease (ESRD). More then 50% of patients with sleep problems tested by polysomnography (PSG) were found to have breathing disturbance during sleep, including sleep apnea (1, 2). The present study was designed to collect data on the prevalence of sleep apnea syndrome in hemodialyzed patients and to analyze the possible influence of hemodialysis on sleep apnea in ESRD patients.


MATERIAL AND METHODS

The study was performed in accordance with the Declaration of Helsinki for human studies and the study protocol was approved by a local Ethics Committee. Sixty-one ESRD patients participated in the study: 24 women (mean age 57.2 ±10.8(SD) yr; duration of hemodialysis 91.0 ±48.6 mo) and 37 men (mean age 58.5 ±13.2 yr; duration of hemodialysis 62.2 ±57.4 mo).

The study consisted of three parts. All patients participated in the first part of the study: a questionnaire-based survey and Epworth Sleepiness Scale (ESS). The patients were asked about loud and irregular snoring, reported incidents of apnea, and daytime sleepiness. The second and third parts consisted of nighttime PSG (Alice3 Polysomnograph, Respironics, Murrysville, PA) performed the night after hemodialysis (17 patients) and between hemodialyses (11 patients). For the PSG recording patients went to bed at their usual time and woke up spontaneously. Six out of the 17 patients from the second part of the study could not complete the following PSG and thus dropped out from the third part. Chi2 test and Fisher’s test were used for data analysis.


RESULTS

The analysis of questionnaires indicated that of the 61 patients, there were 50 without symptoms of sleep apnea (29 men, 21 women), 6 with medium (4 men, 2 women), and 5 with heavy sleep apnea symptoms (1 woman, 4 men) (Table 1). Lack of daytime sleepiness was reported by 35 patients (18 women, 17 men), 15 patients reported medium (2 woman, 13 men), and 11 patients reported heavy daytime sleepiness (4 women, 7 men) (Table 2).

Table 1. Results of questionnaire analysis: 50 points – patients without sleep apnea, 51-52 points – light sleep apnea, 53-58 – medium sleep apnea, 59 – heavy sleep apnea patients.

Table 2. Number of patients as per the score on the Epworth Sleepiness Scale: 9 points – without daytime sleepiness, 10-14 – medium daytime sleepiness, 15 points – heavy daytime sleepiness.

Eleven subjects were involved in the double polysomnographic study: after and between hemodialyses. Based on the number of apneas and hypopneas per hour of sleep (apnea/hypopnea index - AHI) during the night just after hemodialysis we found:
- 4 patients without sleep apnea (AHI 10/h),
- 3 patients with medium sleep apnea (AHI 11-30/h),
- 4 patients with heavy sleep apnea (AHI 31-50/h).

The second nighttime polysomnography performed between hemodialyses showed:
- 4 patients without sleep apnea (AHI 10/h),
- 5 patients with medium sleep apnea (AHI 11-30/h),
- 2 patients with heavy sleep apnea (AHI 31-50/h).

Thus, sleep apnea was found in 7 patients in each of the two polysomnographic nights analyzed (Table 3). In all subjects mixed apneas (central and obstructive) were observed.

Table 3. Apnea-hypopnea index (AHI) in patients just after hemodialysis and between hemodialyses.
n, number of patients

The results of questionnaires showed that only 2 patients of the 11 who participated in all three parts of the study had the characteristics of obstructive sleep apnea (53-58 points) (Table 4). There was no significant correlation between the questionnaire and AHI scores.

Table 4. Questionnaire score and apnea-hypopnea index (AHI).
n, number of patients. There was no correlation between the AHI and questionnaire scores.


DISCUSSION

In the questionnaires, 18% of ERSD patients reported snoring, daytime somnolence, nocturnal apneas events, restless sleep, and headaches. These results are in agreement with other data suggesting that the prevalence of sleep disturbances in patients undergoing chronic dialysis treatment may be at least five times as high as that in the general population (3-8). Our results of the clinical polysomnographic investigation did not correlate with the questionnaire score. However, the prevalence of obstructive sleep apnea found during the double polysomnographic examination (the second and third parts of the current study) was even higher, 7 out of the 11 patients showed pathologically increased AHI. Although these results do not explain the high rate of sleep disorders in the ERSD patient population, they support the opinion that the diagnosis of sleep apnea is of potential significance for the assessment of cardiovascular risk factors in dialyzed patients. Subjective complaints of ERSD patients, typical for sleep apnea, are often overlooked, being mistakenly attributed to the chronic renal failure (3). Thus, the divergence between polysomnographic and questionnaire results is explicable by the complexity of the clinical issue.

Our results confirm the previously reported observation (9) that the procedure of hemodialysis does not change the prevalence of sleep apnea in patients with chronic renal disease. Therefore, the issue why breathing disorders during sleep are eliminated after successful renal transplantation (8, 10) still continues to pose a challenge.

Acknowlegdments: This study was supported by KBN grants 2P05D07226, 2P05B02626, and the statutory activity of the Department of Hygiene, the Department of Epidemiology, and the Department of Physiology of Bydgoszcz Collegium Medicum of the Nicolaus Copernicus University in Torun.


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Author’s address: I. Miskowiec, Department of Hygiene and Epidemiology, Collegium Medicum in Bydgoszcz, Karlowicza 24 St., 85-092 Bydgoszcz, Poland; phone: +48 604 547374.