**2. Subjective complaints in dialysis patients**

Subjective sleep complaints are common in dialysis patients and include difficulty initiating and maintaining sleep, problems with restless, jerking legs, and/or day time sleepiness. Sleep disorders are very inconvenient for the patients and affect their activities of daily living. Most patients believe that relief of these symptoms would improve subjective quality of life. A large number of dialysis patients take sleep-inducing medications. Sleep complaints are more common in elderly patients on dialysis than in younger patients and

Sleep Disorders Associated with Chronic Kidney Disease 387

Nocturnal sleep of patients on dialysis is short and fragmented with total sleep time ranging between 260 and 360 minutes. Sleep efficiency is between 66% and 85% with a large amount of wakeful time (77-135 min), and numerous arousals (25-30/h of sleep) (16-18). Patients have increased patterns of Stage I and Stage II sleep, decreased slow wave (deep sleep), and REM sleep (17, 18). Thus dialysis patients have both reduced quantity and quality of sleep. Changes in sleep patterns in advanced CKD patients who are not on dialysis are similar to

Sleep apnea is classified as obstructive (OSA) due to intermittent closure of the upper airway or central due to intermittent loss of respiratory drive or both (mixed). More than 50% of patients with ESRD have sleep apnea (7, 19). Prevalence appears to be similar in advanced CKD patients who are not on dialysis and those treated with peritoneal or hemodialysis (7, 20). Sleep Disordered Breathing (SDB) is observed with similar frequency in dialysis dependent and dialysis independent CKD patients. Sleep apnea in CKD patients

Sleep apnea in patients with ESRD is mostly obstructive but several observers have reported features of both obstructive and central sleep apnea (16,31). Sleep apnea is caused by both impaired central ventilatory control and upper air way occlusion during sleep. Enhanced ventilatory sensitivity to hypercapnea correlates with apnea severity (22). Conversion from conventional Hemodialysis (CHD) to nocturnal Hemodialysis (NHD) has been associated with reduced severity of sleep apnea due to reduction in ventilatory sensitivity to hypercapnea(31). Upper airway occlusion can be caused by fluid overload and interstitial edema in the upper air way (23). Displacement of fluids from the lower limbs increases neck circumference and pharyngeal resistance and reduces upper air way cross sectional area, contributing to the pathogenesis of obstructive sleep apnea (OSA). Pharyngeal cross sectional area in patients on CHD was smaller than the control, suggesting that this may predispose to upper airway occlusion during sleep (22). Conversion from CHD to NHD is associated with an increase in pharyngeal cross sectional area, possibly due to improve fluid removal(31). Conversion from continuous ambulatory peritoneal dialysis (CAPD) to nocturnal peritoneal dialysis has been shown to reduce the frequency of sleep apnea (24). Upper airway dilator muscle dysfunction due to neuropathy or myopathy associated with chronic uremia or the underlying cause of renal disease such as diabetes mellitus can cause narrowing of pharyngeal muscles (31). There could also be some role for oxidative stress, inflammatory cytokines and middle molecules, all elevated in ESRD in the development of ventilatory instability and or upper airway occlusion,

The apnea –hypopnea index (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 found during polysomnography. Patients with advanced CKD not on dialysis who are non-diabetic are predisposed to more severe AHI as compared to patients with less advanced CKD (25). In patients with diabetes no such association was found probably due to the fact that diabetes itself may be an

**4. Changes in sleep architecture** 

**5. Sleep Apnea Syndrome (SAS)** 

is more frequently obstructive (21).

but this has not been established (66).

**6. Pathogenesis-figure 2** 

patients on dialysis (21)

male patients are more likely to have sleep complaints than women (10). Caucasian patients have a higher prevalence of restless legs syndrome than African American (1, 10). Subjective complaints are also high in patients with increased caffeine intake, pruritis, bone pain, cigarette use, and premature discontinuation of dialysis (1). As in general population, increased stress, anxiety, depression, and worry are also associated with poor subjective sleep quality in dialysis patients (10-12).
