Patrick J. Hanly

Measurement properties of the Epworth sleepiness scale

Obstructive sleep apnea (OSA) has been estimated to affect 2–4% of middle aged adults [1]. Excessive daytime sleepiness is an important criterion both for establishing the severity of OSA and for determining the response to specific treatment such as nasal continuous positive airway pressure (CPAP) [2]. Objective assessment of daytime sleepiness with tests such as the multiple sleep latency test (MSLT) is both time-consuming and costly and is not offered by many sleep disorders clinics [3]. Consequently, a questionnaire that reliably quantifies the severity of daytime sleepiness and that is responsive to changes in daytime sleepiness over time would greatly assist clinicians and researchers in the management and investigation of OSA. Since its publication in 1991, the Epworth sleepiness scale (ESS) has been used by several groups of investigators to measure daytime sleepiness in patients with known or suspected OSA [4]. Furthermore, the ESS has also been used to track changes in daytime sleepiness during treatment of OSA [5,6]. This usage of the ESS as an evaluative instrument that measures change over time may not be appropriate given the original goals of its development and the consequent design of the questionnaire. Furthermore, the use of the ESS as a diagnostic tool may be premature. The objectives of this review are to determine what the ESS actually measures and whether that measurement truly reflects objective sleepiness, and to determine if the ESS can be used to diagnose pathological sleepiness and follow its response to treatment. 2. What does the ESS measure?

Enhanced chemo-responsiveness in patients with sleep apnoea and end-stage renal disease

Although sleep apnoea is very common in patients with end-stage renal disease, the physiological mechanisms for this association have not yet been determined. The current authors hypothesised that altered respiratory chemo-responsiveness may play an important role. In total, 58 patients receiving treatment with chronic dialysis were recruited for overnight polysomnography. A modified Read rebreathing technique, which is used to assess basal ventilation, ventilatory sensitivity and threshold, was completed before and after overnight polysomnography. Patients were divided into apnoeic (nu200a=u200a38; apnoea/hypopnoea index (AHI) 35±22 events·h-1) and nonapnoeic (nu200a=u200a20; AHI 3±3 events·h-1) groups, with the presence of sleep apnoea defined as an AHI >10 events·h-1. While basal ventilation and the ventilatory recruitment threshold were similar between groups, ventilatory sensitivity during isoxic hypoxia (partial pressure of oxygen (PO2) 6.65 kPa) and hyperoxia (PO2 19.95 kPa) was significantly greater in apnoeic patients. Overnight changes in chemoreflex responsiveness were similar between groups. In conclusion, these data indicate that the responsiveness of both the central and peripheral chemoreflexes is augmented in patients with sleep apnoea and end-stage renal disease. Since increased ventilatory sensitivity to hypercapnia destabilises respiratory control, the current authors suggest this contributes to the pathogenesis of sleep apnoea in this patient population.

Sleep quality and daytime function in adults with cystic fibrosis and severe lung disease

It was hypothesized that adult cystic fibrosis (CF) patients with severe lung disease have impaired daytime function related to nocturnal hypoxaemia and sleep disruption. Nineteen CF patients (forced expiratory volume in one second 28±7% predicted) and 10 healthy subjects completed sleep diaries, overnight polysomnography (PSG), and assessment of daytime sleepiness and neurocognitive function. CF patients tended to report more awakenings (0.7±0.5 versus 0.3±0.2·h−1, p=0.08), and PSG revealed reduced sleep efficiency (71±25 versus 93±4%, p=0.004) and a higher frequency of awakenings (4.2±2.7 versus 2.4±1.4·h−1, p=0.06). Mean arterial oxygen saturation during sleep was lower in CF patients (84.4±6.8 versus 94.3±1.5%, p<0.0001) and was associated with reduced sleep efficiency (regression coefficient (r)=0.57, p=0.014). CF patients had short sleep latency on the multiple sleep latency test (6.7±3u2005min). The CF group reported lower levels of activation and happiness and greater levels of fatigue (p<0.01), which correlated with indices of sleep loss, such as sleep efficiency (r=0.47, p=0.05). Objective neurocognitive performance was also impaired in CF patients, reflected by lower throughput for simple addition/subtraction, serial reaction and colour-word conflict. The authors concluded that adult cystic fibrosis patients with severe lung disease have impaired neurocognitive function and daytime sleepiness, which is partly related to chronic sleep loss and nocturnal hypoxaemia.

Pharyngeal narrowing in end-stage renal disease: implications for obstructive sleep apnoea

Sleep apnoea is common in patients with end-stage renal disease (ESRD). It was hypothesised that this is related to a narrower upper airway. Upper airway dimensions in patients with and without ESRD and sleep apnoea were compared, in order to determine whether upper airway changes associated with ESRD could contribute to the development of sleep apnoea. An acoustic reflection technique was used to estimate pharyngeal cross-sectional area. Sleep apnoea was assessed by overnight polysomnography. A total of 44 patients with ESRD receiving conventional haemodialysis and 41 subjects with normal renal function were studied. ESRD and control groups were further categorised by the presence or absence of sleep apnoea (apnoea/hypopnoea index ≥10u2005events·h−1). The pharyngeal area was smaller in patients with ESRD compared with subjects with normal renal function: 3.04±0.84 versus 3.46±0.80u2005cm2 for the functional residual capacity and 1.99±0.51 versus 2.14±0.58u2005cm2 for the residual volume. The pharynx is narrower in patients with ESRD than in subjects with normal renal function. In conclusion, since a narrower upper airway predisposes to upper airway occlusion during sleep, it is suggested that this factor contributes to the pathogenesis of sleep apnoea in dialysis-dependent patients.

DAILY HEMODIALYSIS—SELECTED TOPICS: Sleep Apnea and Daytime Sleepiness in End‐Stage Renal Disease

Sleep disorders are common in patients with end‐stage renal disease (ESRD). The prevalence of sleep apnea is 10 times greater in patients with ESRD than in the general population. Although sleep apnea is not improved by conventional modes of dialysis, it is corrected by nocturnal hemodialysis, which provides a new and unique model to study its pathophysiology in this patient population. In addition to causing sleep disruption and impairment of daytime function, sleep apnea may also increase the cardiovascular morbidity and mortality that is commonly found in patients with ESRD. “Pathological” daytime sleepiness is found in 50% of patients with ESRD. Although its pathogenesis has been related both to sleep apnea and periodic limb movements, it has also been attributed to a variety of metabolic factors, including the severity of uremia. Further research is required to evaluate the impact of sleep disorders on the clinical outcome of patients with ESRD.

Overnight changes of chemoreflex control in obstructive sleep apnoea patients

We hypothesized that the numerous episodes of hypoxia, hypercapnia and arousal experienced by obstructive sleep apnoea (OSA) patients induce overnight changes in respiratory chemoreflexes. A modification of the Read rebreathing technique assessed chemoreflex characteristics in the evening and the morning of patients undergoing diagnostic assessment for OSA in a clinical sleep laboratory. Two groups were studied: those with apnoea-hypopnoea indices (AHI) greater than 30 composed the OSA group (n = 12), and those with AHI indices less than 10 composed the non-OSA group (n = 12). There was a significant (approximately 30%) overnight increase in chemoreflex sensitivities, without changes in thresholds, in the OSA group. In the non-OSA group there was a significant overnight reduction in chemoreflex thresholds (approximately 5%), without changes in sensitivities. We suggest that these changes affect the stability of the chemoreflex control system in opposite ways as the night proceeds: destabilizing breathing for patients in the OSA group, and stabilising breathing for patients in the non-OSA group.

The importance of age and obesity on the relation between diabetes and left ventricular mass

OBJECTIVESnThe study investigated the relation of age with diabetes, obesity and hypertension on left ventricular mass (LVM).nnnBACKGROUNDnEpidemiological studies demonstrate a general rise of LVM with aging, but whether this phenomenon is independent or a function of coexisting diseases that accompany the aging process is unclear. Although obesity, hypertension and diabetes often coexist and increase in prevalence with age, studies of LVM in diabetics have been reported in mostly nonobese populations, and with little regard to the age-hypertension-obesity interactions and effects on LVM.nnnMETHODSnWe prospectively measured LVM in 875 consecutive, mostly obese individuals (673 men, 202 women). Clinical data were obtained by chart review and clinical history. Echocardiographic measurements of LVM (American Society of Echocardiography criteria) were calculated using the Devereux formula and corrected for height2.7 (LVM/Ht).nnnRESULTSnMean age was 49.3+/-12.3 years, body mass index 33.3+/-8.0 kg/m2, and LVM/Ht2.7 41.7+/-13.4 g/m2.7. Of the total cohort, 673 patients were men, 519 obese, 228 hypertensive, and 52 diabetic. Of the 519 obese, 183 were hypertensive and 44 were diabetic (22 of those were hypertensive). Of the 228 hypertensives, 183 were obese and 26 were diabetic. On multivariate analysis, obesity (p = 0.0001), age (p = 0.0001), hypertension (p = 0.0003) and diabetes (p = 0.62) were all independently associated with LVM/Ht2.7. Obesity was the most potent independent predictor of LVM/Ht2.7, associated with an increase of 8.1 g/m2.7 in LVM/Ht2.7. In diabetics, obesity had a synergistic effect on LVM/Ht2.7 (p = 0.006), which was further amplified by age (p = 0.03).nnnCONCLUSIONSnAge, obesity, hypertension and diabetes are all independent determinants of LVM. The magnitude of the effect of diabetes on LVM is mainly consequent to a significant interaction of diabetes with obesity and age.

DAILY HEMODIALYSIS-SELECTED TOPICS: Sleep Apnea and Daytime Sleepiness in End-Stage Renal Disease: APNEA AND SLEEPINESS IN ESRD

Sleep disorders are common in patients with end‐stage renal disease (ESRD). The prevalence of sleep apnea is 10 times greater in patients with ESRD than in the general population. Although sleep apnea is not improved by conventional modes of dialysis, it is corrected by nocturnal hemodialysis, which provides a new and unique model to study its pathophysiology in this patient population. In addition to causing sleep disruption and impairment of daytime function, sleep apnea may also increase the cardiovascular morbidity and mortality that is commonly found in patients with ESRD. “Pathological” daytime sleepiness is found in 50% of patients with ESRD. Although its pathogenesis has been related both to sleep apnea and periodic limb movements, it has also been attributed to a variety of metabolic factors, including the severity of uremia. Further research is required to evaluate the impact of sleep disorders on the clinical outcome of patients with ESRD.