The relationship between periodic limb movement during sleep and dyslipidaemia in patients with obstructive sleep apnea.

Periodic limb movements during sleep and obstructive sleep apnea are both associated with increased sympathetic tone, and have been proposed as risk factors for heart diseases and, in particular, cardiovascular disease. As sympathetic system activation may lead to dyslipidaemia, periodic limb movements during sleep could be an additional risk factor for cardiovascular disease in patients with obstructive sleep apnea. The aim of the study was to determine whether the presence of periodic limb movements during sleep affects serum lipid levels in obstructive sleep apnea. Total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, non- high-density lipoprotein cholesterol and triglyceride levels were investigated in 4138 patients with obstructive sleep apnea in the European Sleep Apnea Database (ESADA) cohort, divided into those with periodic limb movements during sleep index ≥ 15 per hr (n = 628) and controls (n = 3510). ANCOVA adjusted for age, sex, body mass index, apnea-hypopnea index, alcohol intake, smoking status, diabetes, insomnia and study site was used to assess differences in lipids between periodic limb movements during sleep and controls. Patients with periodic limb movements during sleep (24% female, 54.4 ± 12.1 years, body mass index 31.9 ± 5.8 kg m-2 , apnea-hypopnea index 36.7 ± 25.4 per hr) had higher triglyceride (1.81 ± 1.04 versus 1.69 ± 0.90 mmol L-1 , p = 0.002) and lower high-density lipoprotein cholesterol (1.19 ± 0.34 versus 1.24 ± 0.37 mmol L-1 , p = 0.002) levels, whilst there was no difference in either total cholesterol (4.98 ± 1.10 versus 4.94 ± 1.07 mmol L-1 ), low-density lipoprotein cholesterol (3.04 ± 0.96 versus 2.98 ± 0.98 mmol L-1 ) or non- high-density lipoprotein cholesterol (3.78 ± 1.10 versus 3.70 ± 1.05 mmol L-1 ) concentrations (all p > 0.05). The results remained unchanged after most sensitivity analyses. Patients with obstructive sleep apnea with periodic limb movements during sleep had more prevalent cardiovascular disease (11% versus 6%, p < 0.01). Periodic limb movements during sleep in obstructive sleep apnea is associated with dyslipidaemia independently of important confounders. Our results highlight periodic limb movements during sleep as an additional risk factor for cardiovascular disease in obstructive sleep apnea.

Impact of temperature on obstructive sleep apnoea in three different climate zones of Europe: Data from the European Sleep Apnoea Database (ESADA).

Recent studies indicate that ambient temperature may modulate obstructive sleep apnoea (OSA) severity. However, study results are contradictory warranting more investigation in this field. We analysed 19,293 patients of the European Sleep Apnoea Database (ESADA) cohort with restriction to the three predominant climate zones according to the Köppen-Geiger climate classification: Cfb (warm temperature, fully humid, warm summer), Csa (warm temperature, summer dry, hot summer), and Dfb (snow, fully humid, warm summer). Average outside temperature values were obtained and several hierarchical regression analyses were performed to investigate the impact of temperature on the apnea-hypopnea index (AHI), oxygen desaturation index (ODI), time of oxygen saturation <90% (T90) and minimum oxygen saturation (MinSpO2 ) after controlling for confounders including age, body mass index, gender, and air conditioning (A/C) use. AHI and ODI increased with higher temperatures with a standardised coefficient beta (ß) of 0.28 for AHI and 0.25 for ODI, while MinSpO2 decreased with a ß of -0.13 (all results p < .001). When adjusting for climate zones, the temperature effect was only significant in Cfb (AHI: ß = 0.11) and Dfb (AHI: ß = 0.08) (Model 1: p < .001). The presence of A/C (3.9% and 69.3% in Cfab and Csa, respectively) demonstrated only a minor increase in the prediction of the variation (Cfb: AHI, R2 +0.003; and Csa: AHI, R2 +0.007; both p < .001). Our present study indicates a limited but consistent influence of environmental temperature on OSA severity and this effect is modulated by climate zones.

The prevalence of excessive sleepiness is higher in shift workers than in patients with obstructive sleep apnea.

Excessive daytime sleepiness (EDS) is a common feature among shift workers as well as in obstructive sleep apnea (OSA) patients. There are several important accidents related to sleep disturbances causing EDS. The aim of this study was to evaluate EDS in a group of shift workers (regular rotating) from civil aviation and to compare them with OSA patients (n = 300) and with a group of regular workers (RW) (n = 140). Our sample was composed of 730 working-age individuals (aged 18-67 years). The regular rotating shift workers (SW) sample was composed of 290 aeronautical mechanics. EDS was evaluated with the Epworth Sleepiness Scale (ESS) and defined as a score ≥ 11. The prevalence value obtained for the EDS of RW was 37.1%, for SW it was 60.7% and for OSA patients it was 40.7%. A logistic regression model for EDS in a subsample composed of men and matched for age and BMI, controlling for self-reported sleep duration, showed an increased risk of EDS for SW (OR = 3.91, p = .001), with the RW group as reference. OSA patients did not differ from RW on EDS levels. This study emphasizes the presence of EDS in a shift work group of civil aviation professionals, which exceeded the EDS level of a positive control group of OSA patients. Sleep hygiene education for companies' workers and management is important and mitigation strategies should be implemented to reduce excessive sleepiness among workers.

Obstructive sleep apnoea independently predicts lipid levels: Data from the European Sleep Apnea Database.

BACKGROUND AND OBJECTIVE: Obstructive sleep apnoea (OSA) and dyslipidaemia are independent risk factors for cardiovascular disease. This study investigates the association between OSA and plasma lipid concentrations in patients enrolled in the European Sleep Apnea Database (ESADA) cohort. METHODS: The cross-sectional analysis included 8592 patients without physician-diagnosed hyperlipidaemia or reported intake of a lipid-lowering drug (age 50.1 ± 12.7 years, 69.1% male, BMI: 30.8 ± 6.6 kg/m2 , mean apnoea-hypopnoea index (AHI): 25.7 ± 25.9 events/h). The independent relationship between measures of OSA (AHI, oxygen desaturation index (ODI), mean and lowest oxygen saturation) and lipid profile (total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and fasting triglycerides (TG)) was determined by means of general linear model analysis. RESULTS: There was a dose response relationship between TC and ODI (mean ± SE (mg/dL): 180.33 ± 2.46, 184.59 ± 2.42, 185.44 ± 2.42 and 185.73 ± 2.44; P < 0.001 across ODI quartiles I-IV). TG and LDL concentrations were better predicted by AHI than by ODI. HDL-C was significantly reduced in the highest AHI quartile (mean ± SE (mg/dL): 48.8 ± 1.49 vs 46.50 ± 1.48; P = 0.002, AHI quartile I vs IV). Morbid obesity was associated with lower TC and higher HDL-C values. Lipid status was influenced by geographical location with the highest TC concentration recorded in Northern Europe. CONCLUSION: OSA severity was independently associated with cholesterol and TG concentrations.

Decrease of perforin positive CD3+γδ-T cells in patients with obstructive sleep disordered breathing.

INTRODUCTION: Sleep related breathing disorders (SRBD) cause sleep fragmentation, intermittent hypoxia or a combination of both leading to homeostasis perturbations, including in the immune system. We investigated whether SRBD patients with or without intermittent hypoxia show substantial differences in perforin and granzyme-B positive peripheral blood lymphocytes. METHODS: A total of 87 subjects were included and distributed as follows: 24 controls (C), 19 patients with respiratory effort related arousals due to increased upper airway resistance (UAR) without hypoxic events, 24 obese patients with obstructive sleep apnea (OSA) (oOSA), and 20 without obesity (noOSA). After polysomnographic recording, we analyzed in fasting blood samples routine hematologic and biochemical parameters and the percentage of lymphocytes containing the proteins perforin and granzyme-B (GrB). Kruskal-Wallis tests and a posteriori multiple comparisons were applied for statistical analysis of results. RESULTS: Perforin-positive γδ-cells revealed significant differences between groups (p = 0.017), especially between the Control group and the oOSA (p-value = 0.04); the remaining SRBD groups also showed differences from the control (C vs UAR: p = 0.08; C vs noOSA = 0.09), but they did not raise to statistical significance. There were no differences among the SRBD groups. Granzyme-B cells were decreased in SRBD patients, but the differences were not statistically significant. No additional statistical significant result was found in the other investigated lymphocyte subsets. CONCLUSIONS: Obstructive sleep-disordered breathing is associated with a decrease in perforin-positive CD3+γδ-T cells. Although this finding was detected in lean patients without intermittent hypoxia, the reduction was only statistically significant in obese patients with severe OSA. Because CD3+γδ-T cells play an important role in the control of tumor cells, our findings are directly relevant for the study of the association of OSA and cancer.

Arousal burden is highest in supine sleeping position and during light sleep.

STUDY OBJECTIVES: Arousal burden (AB) is defined as the cumulative duration of arousals during sleep divided by the total sleep time. However, in-depth analysis of AB related to sleep characteristics is lacking. Based on previous studies addressing the arousal index (ArI), we hypothesized that the AB would peak in the supine sleeping position and during non-rapid eye movement stage 1 (N1) and show high variability between scorers. METHODS: Nine expert scorers analyzed polysomnography recordings of 50 participants, the majority with an increased risk for obstructive sleep apnea. AB was calculated in different sleeping positions and sleep stages. A generalized estimating equation was utilized to test the association between AB and sleeping positions, sleep stages, and scorers. The correlation between AB and ArI was tested with Spearman's rank-order correlation. RESULTS: AB significantly differed between sleeping positions (p<0.001). The median AB in the supine sleeping position was 47-62% higher than in the left and right position. The AB significantly differed between the sleep stages (p<0.001); the median AB was more than 200% higher during N1 than during other sleep stages. In addition, the AB differed significantly between scorers (p<0.001) and correlated strongly with ArI (r=0.935, p<0.001). CONCLUSIONS: AB depends on the sleeping position, sleep stage, and scorer as hypothesized. AB behaved similarly as the ArI, but the high variability in the ABs between scorers indicates a potential limitation caused by subjective manual scoring. Thus, the development of more accurate techniques for scoring arousals is required before AB can be reliably utilized.

Diagnostic Images of Pulmonary Alveolar Microlithiasis: A Rare, Autosomal Recessive Disorder.

Pulmonary alveolar microlithiasis (PAM) is a genetic lung disorder that is characterized by the accumulation of calcium phosphate deposits in the alveolar spaces of the lung. PAM is discovered incidentally on radiographs performed for other purposes, and the typical disease course is characterized by slowly progressive respiratory failure over decades. Treatment remains supportive. A 62-year-old woman presented in the emergency department with dyspnoea and fatigue. On physical examination she had crackles on pulmonary auscultation and digital clubbing. A CT scan of the chest showed multiple high-density areas throughout the lung parenchyma, suggesting the presence of alveolar microlithiasis. This CT finding is the typical radiological presentation of PAM, while the hallmark presentation is clinical-radiological dissociation. LEARNING POINTS: Pulmonary alveolar microlithiasis (PAM) is a rare genetic lung disorder resulting in accumulation of calcium phosphate deposits in the alveoli.The typical radiological presentation of PAM is the classic 'sandstorm' appearance in the lung.The key to diagnosis of this disease is clinical-radiological dissociation.

Effects of sleep apnea and kidney dysfunction on objective sleep quality in nondialyzed patients with chronic kidney disease: an ESADA study.

STUDY OBJECTIVES: Patients with chronic kidney disease (CKD) often report poor sleep quality, but they commonly exhibit OSA. The aim of this study was to evaluate the influence of OSA severity and of estimated glomerular filtration rate impairment on objective sleep quality in nondialyzed patients with CKD, defined as an estimated glomerular filtration rate <60 mL/min/1.73m². METHODS: Polysomnographic sleep characteristics were compared between patients with (n = 430) and without CKD (n = 6,639) in the European Sleep Apnea Database cohort. Comparisons were repeated in 375 patients with CKD and 375 control patients without CKD matched for sleep center, age, sex, and AHI, and in 310 matched CKD and non-CKD patients without psychiatric disturbances. RESULTS: Among all patients with and without CKD, total sleep time was similar but sleep stage N1 (median 8.7% [IQR 4.8-18.0] vs 6.7% [3.6-12.7], respectively) and sleep stage R (12.6% [6.8-17.7] vs 14.2% [8.8-19.8], respectively) significantly differed (P < .0001). No difference in sleep characteristics was observed between matched patients either with or without psychiatric disturbances. After subdividing the matched patients according to AHI tertile (<25, ≥25 to <49, and ≥49 events/h) and estimated glomerular filtration rate (≥60, 45 to <60, <45 mL/min/1.73m²), we found a significant effect of AHI on sleep stages N2, N3, and R (P < .001), but there was no effect of CKD. CONCLUSIONS: In nondialyzed patients with CKD, objective sleep quality is influenced similarly by AHI as in patients without CKD but is not affected by CKD severity. Previously reported poor sleep quality in CKD may partly result from the high prevalence of OSA in CKD.

The Importance of Sleep Fragmentation on the Hemodynamic Dipping in Obstructive Sleep Apnea Patients.

INTRODUCTION: Obstructive sleep apnea (OSA) has been associated with non-dipping blood pressure (BP). The precise mechanism is still under investigation, but repetitive oxygen desaturation and arousal induced sleep fragmentation are considered the main contributors. METHODS: We analyzed beat-to-beat measurements of hemodynamic parameters (HPs) during a 25-min period of wake-sleep transition. Differences in the mean HP values for heart rate (HR), systolic BP (SBP), and stroke volume (SV) during wake and sleep and their standard deviations (SDs) were compared between 34 controls (C) and 22 OSA patients. The Student's t-test for independent samples and the effect size by Cohen's d (d) were calculated. HP evolution was investigated by plotting the measured HP values against each consecutive pulse wave. After a simple regression analysis, the calculated coefficient beta (SCB) was used to indicate the HP evolution. We furthermore explored by a hierarchical block regression which variables increased the prediction for the SCB: model 1 BMI and age, model 2 + apnea/hypopnea index (AHI), and model 3 + arousal index (AI). RESULTS: Between the two groups, the SBP increased in OSA and decreased in C resulting in a significant difference (p = 0.001; d = 0.92). The SV demonstrated a similar development (p = 0.047; d = 0.56). The wake/sleep variation of the HP measured by the SD was higher in the OSA group-HR: p < 0.001; d = 1.2; SBP: p = 0.001; d = 0.94; and SV: p = 0.005; d = 0.82. The hierarchical regression analysis of the SCB demonstrated in SBP that the addition of AI to AHI resulted in ΔR 2: +0.163 and ΔF + 13.257 (p = 0.001) and for SV ΔR 2: +0.07 and ΔF 4.83 (p = 0.003). The AI but not the AHI remained statistically significant in the regression analysis model 3-SBP: ß = 0.717, p = 0.001; SV: ß = 0.469, p = 0.033. CONCLUSION: In this study, we demonstrated that in OSA, the physiological dipping in SBP and SV decreased, and the variation of all investigated parameters increased. Hierarchical regression analysis indicates that the addition of the AI to BMI, age, and AHI increases the prediction of the HP evolution following sleep onset for both SBP and SV and may be the most important variable.

Occlusal and skeletal effects of an oral appliance in the treatment of obstructive sleep apnea.

STUDY OBJECTIVE: s: Oral appliances (OAs) are considered to be a treatment option for patients with obstructive sleep apnea/hypopnea syndrome (OSAHS). Although the effectiveness of these appliances has been evaluated in a number of clinical trials, there are few follow-up studies concerning the dental and skeletal side effects that, theoretically, could be caused by OAs. We sought to examine the long-term skeletal and occlusal effects of a nocturnally worn activator in adult patients treated for OSAHS. DESIGN: We analyzed the dental casts and lateral radiographs of 34 patients (mean age, 52.9 years; SD, 9.6 years; range, 27.1 to 64.6 years) before initiating treatment and after at least 24 months of treatment (mean length of treatment, 29.6 months; range, 24.1 to 43.5 months; SD, 5.1 months). The OA was worn by each patient 6 to 8 h nightly for > 5 days per week. SETTING: Department of Orthodontics, Dental Medical School, Freiburg, Germany. MEASUREMENTS AND RESULTS: Follow-up polysomnography studies confirmed improved breathing parameters with the use of OAs. A statistically significant alteration in the occlusion was found. The anteroposterior position of the molars and the inclination of the upper and lower incisors were changed. No skeletal changes in the position of the mandible were noted. CONCLUSIONS: The data suggest that in addition to control polysomnographic examinations, regular dental follow-up visits are mandatory when lifelong OSAHS treatment with an OA is being considered for patients with obstructive sleep apnea/hypopnea.

Sleep-related obstructive disordered breathing in cleft palate patients after palatoplasty.

Sleep-disordered breathing is frequently associated with children presenting congenital midface defects. Because of structural and functional anomalies in the upper airway, children with cleft palate, especially after surgery, may carry a higher risk of developing sleep-disordered breathing. However, the presence of such sleep-disordered breathing in older cleft palate children has not been emphasized. The aim of this comparative overnight cardiorespiratory sleep study was to evaluate cleft palate patients according to sleep-disordered breathing. A group of 43 cleft palate children (17 girls and 26 boys; mean age, 12.1 +/- 3.8 years) was compared with a control group of 20 randomly selected, noncleft children matched for age, sex, and body mass index. None of the patients suffered from manifest sleep-disordered breathing. Cleft palate patients had a statistically significantly higher respiratory disturbance index and snoring index, but no increased apnea index. The data suggest that cleft palate patients having undergone primary closure of the palate demonstrate microsymptoms of nocturnal upper airway obstruction.

Cicatricial pemphigoid in the upper aerodigestive tract: diagnosis and management in severe laryngeal stenosis.

Pemphigoid is a group of rare, acquired, autoimmune subepithelial blistering diseases. The condition has been subclassified into bullous pemphigoid and cicatricial pemphigoid (CP). Diagnosis is based on clinical presentation, evidence of subepithelialvesicles or bullae on routine histologic analysis, and direct and indirect immunofluorescence studies. Cicatricial pemphigoid is characterized by linear deposition of immunoreactants, principally IgG and complement factor 3, along epithelial basement membranes. Cicatricial pemphigoid usually leads to mucosal scarring. We present a case of severe CP that led to laryngeal and subglottic stenosis and involvement of both eyes and the oral, nasal, and nasopharyngeal mucosae. Treatment with dapsone, corticosteroids, azathioprine sodium, cyclosporine A, cyclophosphamide, methotrexate sodium, and mycophenolate mofetil between 1997 and 2001 only resulted in temporary disease control. The patient has been treated with leflunomide for the past 8 months, and there have been no relapses. Treatment of CP with leflunomide has not been described in the literature until now.

Cephalometric analysis in patients with obstructive sleep apnea. Part I: diagnostic value.

BACKGROUND: Morphological soft-tissue and skeletal anomalies of the upper extrathoracic airways are considered to be an etiological cofactor of nocturnal obstructive respiratory disorders. PATIENTS AND METHOD: In this study 106 patients with a mean age of 56.1 +/- 8.4 years and a polysomnographic diagnosis of obstructive sleep apnea (OSA) were evaluated roentgenocephalometrically for soft-tissue and skeletal anomalies. Using cluster analysis and multivariate regression analysis, 18 skeletal variables, six pharyngeal variables and five hyoid variables were evaluated as predictor variables under the criterion variable "severity of the disorder". The body mass index (BMI), as a recognized risk factor of OSA, was taken separately into account. RESULTS: No direct correlation was found between the skeletal cephalometric findings and severity of OSA. Only the position of the hyoid as an expression of a probably adaptive alteration to a changed head posture and tongue position was found to be a significant parameter correlating with the severity of OSA. CONCLUSION: Whether cephalometric radiography is of direct diagnostic relevance in the diagnosis of OSA seems questionable in the light of the results of the present study.

Cephalometric analysis in patients with obstructive sleep apnea. Part II: Prognostic value in treatment with a mandibular advancement device.

BACKGROUND: The mandibular advancement device (MAD) is accepted as an additional treatment option for snoring and mild obstructive sleep disorders. Its therapeutic efficacy can only be verified through nocturnal polysomnography with the appliance in situ. The relevance of the craniofacial skeletal and soft-tissue structures as an etiological cofactor is controversial. While the lateral cephalogram of the facial skeleton is of no direct diagnostic relevance, it remains unclear to what extent cephalometric assessment can provide prognostic information to better ensure treatment success with an MAD. METHODS AND RESULTS: This study is based on the evaluation of 57 patients diagnosed polysomnographically with obstructive sleep apnea (OSA). The patients were treated primarily with a modified activator; after 6-12 weeks, control polysomnography was carried out in the sleep laboratory. The cephalometric variables were analyzed using a multivariate regression procedure with the response variable of treatment outcome. In addition to a horizontal craniofacial morphology, the downward and forward posture of the hyoid is a prognostic variable for effective therapy with an MAD.

A comparative study of two mandibular advancement appliances for the treatment of obstructive sleep apnoea.

Mandibular advancement appliances (MAAs) are accepted as a treatment option for snoring and mild obstructive sleep disorders. In the present clinical study two differently designed devices were examined for their effectiveness in treating obstructive sleep apnoea (OSA). The study was based on an assessment of 26 patients with a polysomnographic diagnosis of mild OSA [22 men, four women; mean body mass index 27.3 kg/m2 (SD 3.1); mean age 56.8 years (SD 5.2); mean respiratory disturbance index (RDI): 16.0 events/hour (SD 4.4)]. After insertion of the first MAA and a 6-8-week habituation period, a cardio-respiratory home-sleep study was carried out. Following a 2-3-week period with no treatment, the second appliance was inserted. The sequence of the devices was randomized. Once the patients had become accustomed to the second appliance, another somnographic registration was carried out. Daytime sleepiness, snoring, and sleep quality were assessed subjectively on a visual analogue scale. The results showed that a statistically significant improvement in the respiratory parameters was achieved with both appliances (P < 0.01). However, the activator [RDI: 5.5 events/hour, SD 3.3; apnoea index (AI): 3.4 events/hour, SD 2.1] was significantly more effective (P < 0.01) than the Silencor (RDI, 7.3 events/hour, SD 5.3; AI: 5.8 events/hour, SD 3.2). No difference was recorded in the subjective assessment of the therapeutic effects. Both appliances reduced daytime sleepiness and snoring and improved sleep quality, and both influenced the treatment outcome.

Therapeutic efficacy of an oral appliance in the treatment of obstructive sleep apnea: a 2-year follow-up.

The purpose of this study was to investigate the long-term efficacy of an oral appliance, the Karwetzky activator, on respiratory and sleep parameters in patients with obstructive sleep apnea (OSA). Those selected for this study were 26 patients polysomnographically diagnosed with mild-to-moderate OSA. They were initially treated successfully with this appliance, as documented by a second polysomnographic study after 6 to 12 weeks. Further polysomnographic registrations 6 to 12 months and 18 to 24 months later were performed for each patient wearing the appliance. For 21 patients (81%), therapeutic efficacy was maintained; 5 patients (19%) showed a deterioration in respiratory parameters. We corrected this by adjusting the device in 2 patients. The mean apnea-hypopnea index decreased significantly from 17.8 events per hour at the baseline registration to 4.2 events per hour (P <.001) after 6 to 12 weeks of treatment. After 6 to 12 months, the apnea-hypopnea index was 8.2 events per hour. The index remained at this level 18 to 24 months later, with 8.3 events per hour. Mean oxygen saturation was not improved with the activator, but the number of desaturations had decreased at the 6-to-12 week review. Again, the improvement declined with time, but the number of oxygen desaturations was still significantly decreased at 18 to 24 months (P <.01). Although the respiratory parameters remained statistically improved throughout the study (P <.01), sleep architecture did not change statistically. In most patients, therapeutic efficacy was maintained at the 2-year follow-up, although there was a tendency for effectiveness to fall over time. We concluded that the Karwetzky activator may be an effective treatment alternative for patients with mild-to-moderate OSA, but therapy requires diligent and regular polysomnographic follow-ups. Further long-term studies are needed to assess the continued efficacy of this oral appliance in treating OSA.

Treatment of obstructive sleep apnea with the Karwetzky oral appliance.

The aims of this retrospective study were to assess the effect of a Karwetzky mandibular protrusion appliance for treating patients with mild, moderate, and severe obstructive sleep apnea. Eighty-one of 116 patients (69.8%) suffering from obstructive sleep apnea were treated with an activator model according to Karwetzky. After 4 months (SD 4.0 months) treatment outcome was controlled by polysomnography. Therapeutic outcome depended on the severity of obstructive sleep apnea. The median apnea-hypopnea index decreased from 10.6 events/h (range 2.0-14.9) to 5.8 events/h (range 0.2-17.3, P<0.01) in the mild group, from 21.7 events/h (range 17.3-28.4) to 7.7 events/h (range 1.0-30.1, P<0.001) in the moderate group, and from 42.1 events/h (range 33.2-64.9) to 18.1 events/h (range 2.4-48.8, P<0.001) in the severe group. Sleep variables did not show consistent improvement except for a trend towards more REM sleep and slow-wave sleep. The numbers of retentive teeth did not statistically influence treatment efficacy. Comparing the pre- and post-treatment polysomnographic variables, it was found that the respiratory events rather than sleep stages were significantly reduced by the Karwetzky appliance investigated.