Population-based analysis of sociodemographic predictors, health-related quality of life and health service use associated with obstructive sleep apnoea and insomnia in Australia.

Although there is growing recognition of the effects of living with sleep disorders and the important role of primary care in their identification and management, studies indicate that the detection of sleep apnoea (OSA) and insomnia may still be low. This large representative community-based study (n=2977 adults) used logistic regression models to examine predictors of self-reported OSA and current insomnia and linear regression models to examine the association of these sleep conditions with both mental and physical components of health-related quality of life (HRQoL) and health service use. Overall, 5.6% (95% confidence interval (CI) 4.6-6.7) and 6.8% (95% CI 5.7-7.9) of subjects self-reported OSA (using a single-item question) and current insomnia (using two single-item questions) respectively. Many sociodemographic and lifestyle predictors for OSA and insomnia acted in different directions or showed different magnitudes of association. Both disorders had a similar adverse relationship with physical HRQoL, whereas mental HRQoL was more impaired among those with insomnia. Frequent consultations with a doctor were associated with a lower physical HRQoL across these sleep conditions; however, lower mental HRQoL among those frequently visiting a doctor was observed only among individuals with insomnia. The adverse relationship between sleep disorders and physical and mental HRQoL was substantial and should not be underestimated.

Sleep-disordered breathing in severe mental illness: clinical evaluation of oximetry diagnosis and management limitations.

BACKGROUND: To describe the diagnosis and management pathway of sleep-disordered breathing (SDB) in a sample of patients with severe mental illness (SMI), and to assess the feasibility and patient acceptability of overnight oximetry as a first-step screening method for detecting severe SDB in this population. METHODS: The study was a retrospective audit of patients with SMI seen at a Collaborative Centre for Cardiometabolic Health in Psychosis service who were invited for overnight oximetry between November 2015 and May 2018. The adjusted oxygen desaturation index (ODI) was calculated using 4% desaturation criteria. Results were discussed with a sleep specialist and categorized into a 4-level risk probability tool for SDB. RESULTS: Of 91 adults consenting for overnight oximetry, 90 collected some oximetry data, though 11 of these 90 patients collected technically unsatisfactory oximetry. Thus 79/90 patients (88%) collected adequate oximetry data for at least one night. The oximetry traces suggested likely minimal obstructive sleep apnea (OSA) in 41 cases, moderate to severe OSA in 25 patients, severe OSA in 9 patients and possible obesity hypoventilation syndrome (OHS) in 4 cases. Full polysomnography was recommended for 39 patients but only one-third underwent testing. Nineteen patients were reviewed by a sleep specialist. Of the 10 patients who initiated CPAP, four were considered adherent to treatment. CONCLUSION: Home oximetry may be a pragmatic option for SDB screening in patients with SMI but reliable full diagnostic and management pathways need to be developed.

Sleep interventions for osteoarthritis and spinal pain: a systematic review and meta-analysis of randomized controlled trials.

OBJECTIVES: To determine if sleep interventions improve pain and sleep in people with osteoarthritis (OA) and/or spinal pain compared to control/placebo. DESIGN: Medline, Embase, AMED, PsycINFO, CENTRAL, CINAHL and PEDro were searched from their inception date to July 2017. Keywords relating to "sleep", "OA", "spinal pain", and "randomized controlled trial (RCT)" were combined. Included RCTs investigated the use of sleep interventions for people with OA and/or spinal pain, and measured at least one sleep and health related outcome. Meta-analyses were performed to pool mean differences for pain and sleep quality. PROSPERO: CRD42016036315. RESULTS: Of 1445 unique records, 24 studies were included. Sixteen studies included participants with spinal pain, seven with OA, and one included a mixed population. Sleep interventions included established sleep interventions (ESI) [cognitive behavioural therapy (CBT) and pharmacological interventions], and a range of others. Intervention periods ranged from 4 to 10 weeks. Thirteen studies were of moderate to high quality (PEDro ≥ 6/10). Due to high heterogeneity between studies we also performed sub-group and sensitivity analyses. ESI decreased Insomnia Severity Index (ISI) for people with low back pain (LBP) (pooled mean difference: -6.78/28, 95% confidence interval (95% CI): [-9.47, -4.09], I2 = 40%) and OA (-2.41, [-4.19, -0.63], 0%). However ESI decreased pain for people with LBP (pooled mean difference: visual analogue scale (VAS) -12.77/100, 95% CI: [-17.57, -7.97], I2 = 0%), but not OA (-2.32, [-7.18, 2.54], 27%). CONCLUSION: ESI appeared to improve sleep and pain for people with LBP, and sleep for people with OA. However more vigorous studies need to be conducted.

Increased sexual desire with exogenous testosterone administration in men with obstructive sleep apnea: a randomized placebo-controlled study.

Testosterone (T) deficiency, sexual dysfunction, obesity and obstructive sleep apnea (OSA) are common and often coexist. T prescriptions have increased worldwide during the last decade, including to those with undiagnosed or untreated OSA. The effect of T administration on sexual function, neurocognitive performance and quality of life in these men is poorly defined. The aim of this study was to examine the impact of T administration on sexual function, quality of life and neurocognitive performance in obese men with OSA. We also secondarily examined whether baseline T might modify the effects of T treatment by dichotomizing on baseline T levels pre-specified at 8, 11 and 13 nmol/L. This was a randomized placebo-controlled study in which 67 obese men with OSA (mean age 49 ± 1.3 years) were randomized to receive intramuscular injections of either 1000 mg T undecanoate or placebo at baseline, week 6 and week 12. All participants were concurrently enrolled in a weight loss program. General and sleep-related quality of life, neurocognitive performance and subjective sexual function were assessed before and 6, 12 and 18 weeks after therapy. T compared to placebo increased sexual desire (p = 0.004) in all men, irrespective of baseline T levels. There were no differences in erectile function, frequency of sexual attempts, orgasmic ability, general or sleep-related quality of life or neurocognitive function (all p = NS). In those with baseline T levels below 8 nmol/L, T increased vitality (p = 0.004), and reduced reports of feeling down (p = 0.002) and nervousness (p = 0.03). Our findings show that 18 weeks of T therapy increased sexual desire in obese men with OSA independently of baseline T levels whereas improvements in quality of life were evident only in those with T levels below 8 nmol/L. These small improvements would need to be balanced against potentially more serious adverse effects of T therapy on breathing.

Disturbances in melatonin secretion and circadian sleep-wake regulation in Parkinson disease.

OBJECTIVE: Using salivary dim light melatonin onset (DLMO) and actigraphy, our study sought to determine if Parkinson disease (PD) patients demonstrate circadian disturbance compared to healthy controls. Additionally, our study investigated if circadian disturbances represent a disease-related process or may be attributed to dopaminergic therapy. METHODS: Twenty-nine patients with PD were divided into unmedicated and medicated groups and were compared to 27 healthy controls. All participants underwent neurologic assessment and 14 days of actigraphy to establish habitual sleep-onset time (HSO). DLMO time and area under the melatonin curve (AUC) were calculated from salivary melatonin sampling. The phase angle of entrainment was calculated by subtracting DLMO from HSO. Overnight polysomnography (PSG) was performed to determine sleep architecture. RESULTS: DLMO and HSO were not different across the groups. However, the phase angle of entrainment was more than twice as long in the medicated PD group compared to the unmedicated PD group (U = 35.5; P = .002) and was more than 50% longer than controls (U = 130.0; P = .021). The medicated PD group showed more than double the melatonin AUC compared to the unmedicated group (U = 31; P = 0.001) and controls (U = 87; P = .001). There was no difference in these measures comparing unmedicated PD and controls. CONCLUSIONS: In PD dopaminergic treatment profoundly increases the secretion of melatonin. Our study reported no difference in circadian phase and HSO between groups. However, PD patients treated with dopaminergic therapy unexpectedly showed a delayed sleep onset relative to DLMO, suggesting dopaminergic therapy in PD results in an uncoupling of circadian and sleep regulation.

Hours of work and rest in the rail industry.

Currently, the National Transport Commission is considering four options to form the regulatory framework for rail safety within Australia with respect to fatigue. While the National Transport Commission currently recommends no limitations around hours of work or rest, we provide evidence which suggests regulatory frameworks should incorporate a traditional hours of service regulation over more flexible policies. Our review highlights: Shift durations >12 h are associated with a doubling of risk for accident and injury. Fatigue builds cumulatively with each successive shift where rest in between is inadequate (<12 h). A regulatory framework for fatigue management within the rail industry should prescribe limits on hours of work and rest, including maximum shift duration and successive number of shifts. Appropriately, validated biomathematical models and technologies may be used as a part of a fatigue management system, to augment the protection afforded by limits on hours of work and rest. A comprehensive sleep disorder screening and management programme should form an essential component of any regulatory framework.

Sleep, blood pressure and obesity in 22,389 New Zealanders.

AIM: To determine the relationship of sleep disorders with blood pressure and obesity in a large, relatively healthy, community-based cohort. METHODS: A cross-sectional study was undertaken using data from 22,389 volunteer blood donors in New Zealand aged 16-84 years. Height, weight, neck circumference and blood pressure were measured directly, and data on sleep and other factors were ascertained using a validated self-administered questionnaire. RESULTS: Even in a relatively young, non-clinical cohort, lack of sleep (34%), snoring (33%), high blood pressure (20%) and obesity (19%) are common. After adjusting for relevant confounders, participants at high risk of sleep apnoea had double the odds of having high blood pressure but only in participants over 40 years. Very low and high quantities of sleep are also associated with high blood pressure. Even after controlling for neck circumference, self-reported sleep apnoea, sleep dissatisfaction and low amounts of sleep are associated with a higher body mass index. CONCLUSIONS: Obesity and hypertension have significant associations with a variety of sleep disorders, even in those less than 40 years of age and after adjusting for a wide range of potential confounders.

Self-reported sleep apnoea and mortality in patients from the Swedish Obese Subjects study.

Sleep apnoea is associated with increased mortality in sleep clinic and community population groups. It is unclear whether a clinical report of sleep apnoea results in additional mortality risk in patients with severe obesity. The Swedish Obese Subjects (SOS) study is a nonrandomised controlled trial of bariatric surgery versus conventional treatment for the treatment of severe obesity and its complications (mean ± SD body mass index 41 ± 5 kg · m(-2)). The presence or absence of sleep apnoea (witnessed pauses in breathing) was determined by self-reporting at baseline in 3,953 patients who were observed for 54,236 person-yrs (mean 13.5 maximum 21.0 yrs). Sleep apnoea was reported by 934 (23.6%) patients at baseline and was a significant univariate predictor of mortality (hazard ratio (95% CI) 1.74 (1.40-2.18)). In a range of multivariate models of mortality risk, controlling for ≤ 16 other potential confounders and established mortality risk factors, sleep apnoea remained a significant prognostic factor (fully adjusted model 1.29 (1.01-1.65)). Self-reported sleep apnoea is an independent prognostic marker of all-cause mortality in obese patients.

Nasopharyngoscopic evaluation of oral appliance therapy for obstructive sleep apnoea.

This study aimed to explore the effect of mandibular advancement splints (MAS) on upper airway anatomy during wakefulness in obstructive sleep apnoea (OSA). Patients commencing treatment for OSA with MAS were recruited. Response to treatment was defined by a >or=50% reduction in the apnoea/hypopnoea index. Nasopharyngoscopy was performed in the supine position. Nasopharyngoscopy was performed in 18 responders and 17 nonresponders. Mandibular advancement caused an increase in the calibre of the velopharynx (mean+/- sem +40+/-10%), with relatively minor changes occurring in the oropharynx and hypopharynx. An increase in cross-sectional area of the velopharynx with mandibular advancement occurred to a greater extent in responders than nonresponders (+56+/-16% versus +22+/-13%; p<0.05). Upper airway collapse during the Müller manoeuvre, relative to the baseline cross-sectional area, was greater in nonresponders than responders in the velopharynx (-94+/-4% versus -69+/-9%; p<0.01) and oropharynx (-37+/-6% versus -16+/-3%; p<0.01). When the Müller manoeuvre was performed with mandibular advancement, airway collapse was greater in nonresponders than responders in the velopharynx (-80+/-11% versus +9+/-37%; p<0.001), oropharynx (-36+/-6% versus -20+/-5%; p<0.05) and hypopharynx (-64+/-6% versus -42+/-6%; p<0.05). These results indicate that velopharyngeal calibre is modified by MAS treatment and this may be useful for predicting treatment response.

Nocturnal non-invasive nasal ventilation in stable hypercapnic COPD: a randomised controlled trial.

BACKGROUND: Sleep hypoventilation has been proposed as a cause of progressive hypercapnic respiratory failure and death in patients with severe chronic obstructive pulmonary disease (COPD). A study was undertaken to determine the effects of nocturnal non-invasive bi-level pressure support ventilation (NIV) on survival, lung function and quality of life in patients with severe hypercapnic COPD. METHOD: A multicentre, open-label, randomised controlled trial of NIV plus long-term oxygen therapy (LTOT) versus LTOT alone was performed in four Australian University Hospital sleep/respiratory medicine departments in patients with severe stable smoking-related COPD (forced expiratory volume in 1 s (FEV1.0) <1.5 litres or <50% predicted and ratio of FEV1.0 to forced vital capacity (FVC) <60% with awake arterial carbon dioxide tension (PaCO2) >46 mm Hg and on LTOT for at least 3 months) and age <80 years. Patients with sleep apnoea (apnoea-hypopnoea index >20/h) or morbid obesity (body mass index >40) were excluded. Outcome measures were survival, spirometry, arterial blood gases, polysomnography, general and disease-specific quality of life and mood. RESULTS: 144 patients were randomised (72 to NIV + LTOT and 72 to LTOT alone). NIV improved sleep quality and sleep-related hypercapnia acutely, and patients complied well with therapy (mean (SD) nightly use 4.5 (3.2) h). Compared with LTOT alone, NIV (mean follow-up 2.21 years, range 0.01-5.59) showed an improvement in survival with the adjusted but not the unadjusted Cox model (adjusted hazard ratio (HR) 0.63, 95% CI 0.40 to 0.99, p = 0.045; unadjusted HR 0.82, 95% CI 0.53 to 1.25, p = NS). FEV1.0 and PaCO2 measured at 6 and 12 months were not different between groups. Patients assigned to NIV + LTOT had reduced general and mental health and vigour. CONCLUSIONS: Nocturnal NIV in stable oxygen-dependent patients with hypercapnic COPD may improve survival, but this appears to be at the cost of worsening quality of life. TRIAL REGISTRATION NUMBER: ACTRN12605000205639.

Randomised trial of CPAP vs bilevel support in the treatment of obesity hypoventilation syndrome without severe nocturnal desaturation.

BACKGROUND: Untreated, obesity hypoventilation is associated with significant use of health care resources and high mortality. It remains unclear whether continuous positive airway pressure (CPAP) or bilevel ventilatory support (BVS) should be used as initial management. The aim of this study was to determine if one form of positive pressure is superior to the other in improving daytime respiratory failure. METHODS: A prospective randomised study was performed in patients with obesity hypoventilation referred with respiratory failure. After exclusion of patients with persisting severe nocturnal hypoxaemia (Spo(2) < 80% for > 10 min) or carbon dioxide retention (> 10 mm Hg) despite optimal CPAP, the remaining patients were randomly assigned to receive either CPAP or BVS over a 3-month period. The primary outcome was change in daytime carbon dioxide level. Secondary outcome measures included daytime sleepiness, quality of life, compliance with treatment and psychomotor vigilance testing. RESULTS: Thirty-six patients were randomised to either home CPAP (n = 18) or BVS (n = 18). The two groups did not differ significantly at baseline with regard to physiological or clinical characteristics. Following 3 months of treatment, daytime carbon dioxide levels decreased in both groups (CPAP 6 (8) mm Hg; BVS 7 (7) mm Hg) with no between-group differences. There was no difference in compliance between the two treatment groups (5.8 (2.4) h/night CPAP vs 6.1 (2.1) h/night BVS). Although both groups reported an improvement in daytime sleepiness, subjective sleep quality and psychomotor vigilance performance were better with BVS. CONCLUSIONS: Both CPAP and BVS appear to be equally effective in improving daytime hypercapnia in a subgroup of patients with obesity hypoventilation syndrome without severe nocturnal hypoxaemia. TRIAL REGISTRATION NUMBER: Australian Clinical Trials Registry ACTRN01205000096651.

Sleep health New South Wales: chronic sleep restriction and daytime sleepiness.

AIMS: The aim of this study was to provide the first population-based descriptions of typical sleep duration and the prevalence of chronic sleep restriction and chronic sleepiness in community-dwelling Australian adults. METHODS: Ten thousand subjects randomly selected from the New South Wales electoral roll, half aged 18-24 years and the other half aged 25-64 years were posted a questionnaire asking about sleep behaviour, sleepiness and sleep disorders. RESULTS: Responses were received from 3300 subjects (35.6% response rate). The mean +/- standard deviation of sleep duration was 7.25 +/- 1.48 h/night during the week and 7.53 +/- 2.01 h/night in the weekends. Of the working age group, 18.4% reported sleeping less than 6.5 h/night. Chronic daytime sleepiness was present in 11.7%. Logistic modelling indicated that the independent risk factors for excessive daytime sleepiness were being older, sleeping less than 6.5 h per night during the week, getting qualitatively insufficient sleep, having at least one symptom of insomnia and lacking enthusiasm (marker of depression). CONCLUSION: In New South Wales almost one-fifth of the people are chronically sleep restricted and 11.7% are chronically sleepy. Chronic sleepiness was most commonly associated with voluntarily short sleep durations and symptoms of insomnia and depression. If the experimentally observed health effects of sleep restriction also operate at a population level, this prevalence of chronic sleep restriction is likely to have a significant influence on public health in Australia.

Influence of constant positive airway pressure therapy on lipid storage, muscle metabolism and insulin action in obese patients with severe obstructive sleep apnoea syndrome.

AIM: To observe the effect of constant positive airway pressure (CPAP) therapy on regional lipid deposition, muscle metabolism and glucose homeostasis in obese patients with obstructive sleep apnoea syndrome (OSAS). METHODS: A total of 29 obese patients underwent assessment before and after a minimum of 12-week CPAP therapy. Abdominal adipose tissue was assessed using magnetic resonance imaging. Intramyocellular lipid (IMCL) and skeletal muscle creatine were assessed using (1)H-magnetic resonance spectroscopy. Fasting venous and arterial blood were collected. Glucose control was assessed using the homeostatic model. A subgroup of six patients were also evaluated for skeletal muscle pH, phosphocreatine (PCr) and mitochondrial function using (31)P-magnetic resonance spectroscopy. The sample was divided according to CPAP therapy, with regular users defined as a minimum nightly use of >or=4 h; 19 subjects were regular and 10 were irregular CPAP users. RESULTS: Visceral adipose tissue volume and circulating leptin were reduced with regular CPAP use but not with irregular CPAP use. Regular CPAP use also produced an increase in skeletal muscle creatine and resting PCr and a decrease in muscle pH. Neither the regular nor irregular CPAP users showed any change in IMCL content, insulin sensitivity scores or mitochondrial function. CONCLUSIONS: These data show that regular CPAP therapy reduces visceral adipose tissue and leptin and improves skeletal muscle metabolites. In obese patients with severe OSAS, regular CPAP use does not improve glucose control, suggesting that the influence of obesity on glucose control dominates over any potential effect of OSAS.

The effect of sibutramine-assisted weight loss in men with obstructive sleep apnoea.

OBJECTIVE: Obstructive sleep apnoea (OSA) occurs frequently in obese patients and may be reversible with weight loss. Obstructive sleep apnoea and obesity are both independent risk factors for hypertension and increased sympathetic activity. Sibutramine has been increasingly used in the management of obesity, but is relatively contraindicated in patients with hypertension. No studies have investigated the effect of sibutramine on OSA, blood pressure and heart rate. We aimed to assess the changes in OSA and cardiovascular parameters in obese men with OSA enrolled in a sibutramine-assisted weight loss programme (SIB-WL). DESIGN: Open uncontrolled cohort study of obese male subjects with OSA in an SIB-WL. SUBJECTS: Eighty-seven obese (body mass index =34.2+/-2.8 kg/m(2)) middle-aged (46.3+/-9.3 years) male subjects with symptomatic OSA (Epworth score 13.4+/-3.6; respiratory disturbance index (RDI) 46.0+/-23.1 events/h) completed the study. RESULTS: At 6 months, there was significant weight loss (8.3+/-4.7 kg, P<0.0001), as well as a reduction in waist and neck circumference and sagittal height (all P<0.0001). These changes were accompanied by a reduction in OSA severity (RDI fell by 16.3+/-19.4 events/h and Epworth score by 4.5+/-4.6), both P<0.0001). There was no significant change to systolic (P=0.07) or diastolic blood pressure (P=0.87); however, there was a mild rise in resting heart rate (P<0.0001). CONCLUSION: Moderate (approximately 10%) weight loss with SIB-WL results in improvement in OSA severity without increase in blood pressure in closely monitored OSA subjects.

Shift work and work injury in the New Zealand Blood Donors' Health Study.

OBJECTIVE: To investigate associations between work patterns and the occurrence of work injury. METHODS: A cross sectional analysis of the New Zealand Blood Donors Health Study conducted among the 15 687 (70%) participants who reported being in paid employment. After measurement of height and weight, a self-administered questionnaire collected information concerning occupation and work pattern, lifestyle behaviour, sleep, and the occurrence of an injury at work requiring treatment from a doctor during the past 12 months. RESULTS: Among paid employees providing information on work pattern, 3119 (21.2%) reported doing shift work (rotating with nights, rotating without nights, or permanent nights) and 1282 (8.7%) sustained a work injury. In unadjusted analysis, work injury was most strongly associated with employment in heavy manual occupations (3.6, 2.8 to 4.6) (relative risk, 95% CI), being male (1.9, 1.7 to 2.2), being obese (1.7, 1.5 to 2.0), working rotating shifts with nights (2.1, 1.7 to 2.5), and working more than three nights a week (1.9, 1.6 to 2.3). Snoring, apnoea or choking during sleep, sleep complaints, and excessive daytime sleepiness were also significantly associated with work injury. When mutually adjusting for all significant risk factors, rotating shift work, with or without nights, remained significantly associated with work injury (1.9, 1.5 to 2.4) and (1.8, 1.2 to 2.6), respectively. Working permanent night shifts was no longer significantly associated with work injury in the adjusted model. CONCLUSION: Work injury is highly associated with rotating shift work, even when accounting for increased exposure to high risk occupations, lifestyle factors, and excessive daytime sleepiness.

Nasal versus full face mask for noninvasive ventilation in chronic respiratory failure.

This study was undertaken to determine the efficacy of nasal mask (NM) versus full face mask (FFM) for the delivery of noninvasive ventilation (NIV) in subjects with nocturnal hypoventilation. A total of 16 patients (11 males) were enrolled, all with nocturnal hypoventilation currently treated at home with NIV via pressure preset devices. Subjects underwent full polysomnography on three occasions; on the first night current therapy on NM was reviewed, followed by two experimental studies in randomised order using either NM or FFM. NIV settings and oxygen flow rate were the same under both conditions. Notably, 14 of the 16 subjects required the use of a chinstrap to minimise oral leak. Apnoea-hypopnoea indices were within normal limits under both conditions (1.7 +/- 3.4 NM versus 1.6 +/- 2.4 h FFM). The type of interface did not significantly affect gas exchange during sleep (minimum average arterial oxyhaemoglobin saturation total sleep time 93.4 +/- 2.1 NM versus 92.8 +/- 2.5% FFM, Delta transcutaneous carbon dioxide nonrapid eye movement sleep to rapid eye movement sleep (0.58 +/- 0.36 NM versus 0.50 +/- 0.40 kPa FFM). Sleep efficiency was significantly reduced on the FFM (78 +/- 9 NM versus 70 +/- 14% FFM), although arousal indices were comparable under both conditions (15.6 +/- 9.8 NM versus 15.8 +/- 8.8 h FFM). Full face masks appear to be as effective as nasal masks in the delivery of noninvasive ventilation to patients with nocturnal hypoventilation. However, a chinstrap was required to reduce oral leak in the majority of subjects using the nasal mask.

Prophylactic nasopharyngeal tube insertion prevents acute hypoxaemia due to upper-airway obstruction during flexible bronchoscopy.

Insertion of a nasopharyngeal tube (NT) is a highly effective approach to the management of acute hypoxaemia during flexible bronchoscopy (FB) in lung -transplant recipients. We noted that lung transplant recipients undergoing FB who had been treated previously with NT insertion had further episodes of oxygen desaturation (<90%), despite supplemental oxygen therapy. Prophylactic NT insertion prevented acute hypoxaemia in the majority of lung transplant recipients, with previously documented FB-related oxygen desaturation secondary to UAO. Additional jaw support may be needed in some patients with severe upper-airway obstruction.

Sleep hypoventilation in hypercapnic chronic obstructive pulmonary disease: prevalence and associated factors.

Sleep hypoventilation (SH) may be important in the development of hypercapnic respiratory failure in chronic obstructive pulmonary disease (COPD). The prevalence of SH, associated factors, and overnight changes in waking arterial blood gases (ABG), were assessed in 54 stable hypercapnic COPD patients without concomitant sleep apnoea or morbid obesity. Lung function assessment, anthropomorphic measurements, and polysomnography with ABG measurement before and after sleep were conducted in all patients. Transcutaneous carbon dioxide tension (Pt,CO2) was measured in sleep, using simultaneous arterial carbon dioxide tension (Pa,CO2) for in vivo calibration and to correct for drift in the sensor. Of the patients, 43% spent > or = 20% of sleep time with Pt,CO2 > 1.33 kPa (10 mmHg) above waking baseline. Severity of SH was best predicted by a combination of baseline Pa,CO2, body mass index and per cent rapid-eye movement (REM) sleep. REM-related hypoventilation correlated significantly with severity of inspiratory flow limitation in REM, and with apnoea/hypopnoea index. Pa,CO2 increased mean+/-SD 0.70+/-0.65 kPa (5.29+/-4.92 mmHg) from night to morning, and this change was highly significant. The change in Pa,CO2 was strongly correlated with severity of SH. Sleep hypoventilation is common in hypercapnic chronic obstructive pulmonary disease, and related to baseline arterial carbon dioxide tension, body mass index and indices of upper airway obstruction. Sleep hypoventilation is associated with significant increases in arterial carbon dioxide tension night-to-morning, and may contribute to long-term elevations in arterial carbon dioxide tension.