**8. Diagnosis**

Subjective sleepiness can be assessed with a number of simple scales, such as the Epworth Sleepiness Scale (ESS) or the Stanford Sleepiness Scale. The ESS is a self-administered

overriding factor for the development of sleep apnea (25). It was also found that AHI index

Obesity is not required for ESRD patients to develop sleep apnea. Snoring is less intense in patients with CKD who have sleep apnea than in patients with sleep apnea with normal

Sleep apnea worsens the symptoms of CKD such as daytime fatigue, sleepiness, and impaired neurocognitive function. Hypoxemia during sleep is associated with nocturnal hypertension, left ventricular hypertrophy, impaired sympathovagal balance, and increased risk of cardiovascular complications including death (68-69). Sleep apnea may exacerbate the infectious complications common in ESRD patients because sleep disruption and deprivation degrade immune function (26). Severe sleep apnea is an independent predictor

Subjective sleepiness can be assessed with a number of simple scales, such as the Epworth Sleepiness Scale (ESS) or the Stanford Sleepiness Scale. The ESS is a self-administered

correlated weakly with urea level in all patients, but not with creatinine clearance.

Fig. 2. Pathogenesis of sleep Apnea Syndrome (SAS).

of graft loss among female kidney transplant patients (27).

renal function (67).

**8. Diagnosis** 

**7. Clinical significance** 

SAS

questionnaire with 8 questions and is more commonly used. It provides a measure of a person's general level of daytime sleepiness, or their average sleep propensity in daily life .The ESS asks people to rate, on a 4-point scale (0 – 3), their usual chances of dozing off or falling asleep in 8 different situations or activities that most people engage in as part of their daily lives. The total ESS score is the sum of 8 item-scores and can range between 0 and 24.The higher the score, the higher the person's level of daytime sleepiness. Most people can answer the ESS, without assistance, in 2 or 3 minutes. (www.sleepfoundation.org).

Although the characteristic features of sleep apnea may be absent, a history of snoring, witnessed apnea during sleep, and day time sleepiness are suggestive of sleep apnea. Objective diagnostic testing includes home ambulatory monitoring which records air flow, snoring, respiratory movement, oxygen saturation, and heart rate.

Polysomnography (PSG), also known as a sleep study is a nocturnal, laboratory- test used in the diagnosis of Sleep Apnea Syndrome (SAS). It is often considered the standard for diagnosing OSAS, determining the severity of the disease, and evaluating various other sleep disorders that can exist with or without OSAS. PSG consists of a simultaneous recording of multiple physiologic parameters related to sleep and wakefulness. It generally includes monitoring of the patient's airflow through the nose and mouth, blood pressure, heartbeat as measured by an electrocardiograph, blood oxygen level,EEG wave patterns, eye movements(EOG), and the movements of respiratory muscles and limbs(EMG).

Polysomnography can be performed in a sleep laboratory or center and includes comprehensive monitoring of respiration, sleep stages and leg movements. Polysomnography is used to quantify the Apnea-Hypopnea Index (AHI). AHI is an index used to assess the severity of sleep apnea based on the total number of complete cessations (apnea) and partial obstructions (hypopnea) of breathing occurring per hour of sleep. These pauses in breathing must last for at least 10 seconds and be associated with a 3% or greater decrease in oxygenation of the blood. To determine AHI, add the total number of apnea events, plus hypopnea events and divide by the total number of minutes of actual sleep time, then multiply by 60.For example:

Apnea + Hypopnea divided by actual sleep time, then multiply by 60 200 apneas, 200 Hypopneas (400 Total Events) 420 Minutes Actual Sleep Time (7 hours x 60) Divide 400 by 420 = .95 x 60 = 57 AHI (Severe OSA)

In general, the AHI can be used to classify the severity of disease (mild 5-15, moderate 16-30, and severe greater than 30).

Multiple Sleep Latency Test (MSLT) and the Maintenance of Wakefulness Test (MWT) can be considered for the evaluation of day time sleepiness. MSLT is used to measure the time elapsed from the start of a daytime nap period to the first signs of sleep, called sleep latency. The test is based on the idea that the sleepier people are, the faster they will fall asleep. The MWT is a daytime polysomnographic procedure which quantifies wake tendency by measuring the ability to remain awake during sleep conducive circumstances. The test isolates a person from factors that can influence sleep such as temperature, light, and noise. Furthermore, the patient is also advised to not take any hypnotics, drink alcohol, or smoke before or during the test. After allowing the patient to lie down on the bed, the time between lying down and falling asleep is measured and used to determine one's daytime sleepiness.

Sleep Disorders Associated with Chronic Kidney Disease 391

Fig. 4. Improvement of Sleep Apnea with Nocturnal Hemodialysis.

although the mechanism and implications are not understood. (34).

**10. Restless leg syndrome and periodic limb movement disorder** 

Although case reports have indicated correction of sleep apnea after successful kidney transplantation (32), preliminary results from case series suggest that sleep apnea resolves only in a minority of patients after kidney transplantation (33). The administration of branched chain amino acids has shown improvement in apnea index in one patient,

Restless leg syndrome (RLS) is a disorder characterized by sensation that usually occurs prior to sleep onset and causes an almost irresistible urge to move the legs, resulting in delayed sleep onset and disrupted sleep (35). RLS may be idiopathic or secondary to other conditions such as pregnancy, rheumatoid arthritis or uremia. Almost 80% of patients with RLS also have periodic limb movement disorder (PLMD), a condition characterized by

RLS has been reported in 14-23% in patient on CHD and 20-57% in CKD patients (21, 36). The prevalence of PLMD is greater than 50% in CHD and CAPD(see glossary) population (1, 2, 35-38). RLS has also been reported to be 4.5% in transplanted patients. The prevalence of RLS is significantly lower in transplant patients than in patients on maintenance dialysis.

RLS and PMLD may be equally important as sleep apnea in patients with CKD. RLS severity score has been correlated to self perceived sleep problems, nocturnal awakening,

episodic limb movements associated with nocturnal awakening and disrupted sleep.

Declining renal function is associated with increasing prevalence of RLS.
