Is sleep bruxism in obstructive sleep apnea only an oral health related problem?

BACKGROUND: The etiology of sleep bruxism in obstructive sleep apnea (OSA) patients is not yet fully clarified. This prospective clinical study aimed to investigate the connection between probable sleep bruxism, electromyographic muscle tone, and respiratory sleep patterns recorded during polysomnography. METHODS: 106 patients with OSA (74 males, 31 females, mean age: 56.1 ± 11.4 years) were divided into two groups (sleep bruxism: SB; no sleep bruxism: NSB). Probable SB were based on the AASM criteria: self-report of clenching/grinding, orofacial symptoms upon awakening, abnormal tooth wear and hypertrophy of the masseter muscle. Both groups underwent clinical examination for painful muscle symptoms aligned with Temporomandibular Disorders Diagnostic Criteria (DC/TMD), such as myalgia, myofascial pain, and headache attributed to temporomandibular disorder. Additionally, non-complaint positive muscle palpation and orofacial-related limitations (Jaw Functional Limited Scale-20: JFLS-20) were assessed. A one-night polysomnography with electromyographic masseter muscle tone (EMG) measurement was performed. Descriptive data, inter-group comparisons and multivariate logistic regression were calculated. RESULTS: OSA patients had a 37.1% prevalence of SB. EMG muscle tone (N1-N3, REM; P = 0.001) and the number of hypopneas (P = 0.042) were significantly higher in the sleep bruxism group. While measures like apnea-hypopnea-index (AHI), respiratory-disturbance-index (RDI), apnea index (AI), hypopnea-index (HI), number of arousals, and heart rate (1/min) were elevated in sleep bruxers, the differences were not statistically significant. There was no difference in sleep efficiency (SE; P = 0.403). Non-complaint masseter muscle palpation (61.5%; P = 0.015) and myalgia (41%; P = 0.010) were significant higher in SB patients. Multivariate logistic regression showed a significant contribution of EMG muscle tone and JFLS-20 to bruxism risk. CONCLUSION: Increased EMG muscle tone and orofacial limitations can predict sleep bruxism in OSA patients. Besides, SB patients suffer more from sleep disorder breathing. Thus, sleep bruxism seems to be not only an oral health related problem in obstructive apnea. Consequently, interdisciplinary interventions are crucial for effectively treating these patients. TRIAL REGISTRATION: The study was approved by the Ethics Committee of Philipps-University Marburg (reg. no. 13/22-2022) and registered at the "German Clinical Trial Register, DRKS" (DRKS0002959).

[Analysis of Snoring in Patients with Obstructive Sleep Apnea (OSA) by Polysomnography and LEOSound]. / Die Analyse von Schnarchen bei Patienten mit obstruktiver Schlafapnoe (OSA) anhand von Polysomnographie und LEOSound.

INTRODUCTION: Snoring was monitored in patients with obstructive sleep apnea (OSA) using the LEOSound-Monitor and simultaneously polysomnographic (PSG) recording. In obstructive apneas snoring is normally apparent after apnea termination and the beginning of ventilation. We wanted to know how often obstructive apneas are terminated by ventilation in combination with snoring. METHODS AND INTENTION: In 40 patients with OSA (AHI > 15/h) simultaneous polysomnographic recordings were performed amongst long-term respiratory sound monitoring using the LEOSound monitor. Patients' average age was 57±11 years. Average weight was 100±19 kg by a mean body mass index (BMI) of 33±7 kg/m2. 12 out of 40 recordings had to be rejected for further analysis because of artifacts. Snoring recorded by polysomnography was compared with snoring monitored by LEOSound. RESULTS: 3778 obstructive apnea episodes were monitored. LEOSound identified snoring in 1921 (51,0%), polysomnography in 2229 (58,8%) obstructive apneas. Only in one patient there was a higher difference in snoring episodes between PSG and LEOSound. DISCUSSION: In nearly 60% of obstructive apnea events we found snoring during apnea-terminating hyperpnoea. LEOSound is a good diagnostic tool to monitor snoring. It is necessary to clarify why only 60% of all obstructive events/hyperpnoea develop snoring. From a pathophysiological point of view opening of collapsed upper airway should lead in a very high percentage to turbulences in airstream and committed snoring.

[Differential diagnosis of hypersomnia in surgical sleep medicine-more than just sleep apnea!] / Differenzialdiagnostik der Hypersomnie in der operativen Schlafmedizin ­ mehr als nur Schlafapnoe!

Otorhinolaryngologists play a vital role in the management of patients with obstructive sleep apnea (OSA) in Germany, particularly with regards to outpatient diagnostics as well as conservative and surgical treatment of patients with intolerance to ventilation therapy. Although establishment of differential indications for surgical therapy and performance of additional preoperative drug-induced sleep endoscopy in patients with sleep-disordered breathing are among the core competencies of otorhinolaryngologists, differential diagnostic considerations and detection of comorbid sleep disorders can be challenging, particularly for those without extensive sleep medicine training and experience. However, detection of comorbid sleep disorders is of particular importance when permanent surgical treatment is considered. Daytime sleepiness is the typical leading symptom of OSA; nevertheless, other disorders of hypersomnolence need to be considered in these patients and can easily be overlooked. This may lead to inadequate indications for surgical treatment. Based on two case reports, narcolepsy is presented as a comorbid disorder and differential diagnosis in patients with OSA.

[Analysis of Snoring in Patients with Obstructive Sleep Apnea (OSA) by Polysomnography and LEOSound]. / Die Analyse von Schnarchen bei Patienten mit obstruktiver Schlafapnoe (OSA) anhand von Polysomnografie und LEOSound.

INTRODUCTION: Snoring was monitored in patients with obstructive sleep apnea (OSA) using the LEOSound-Monitor and simultaneously polysomnographic (PSG) recording. In obstructive apneas snoring is normally apparent after apnea termination and the beginning of ventilation. We wanted to know how often obstructive apneas are terminated by ventilation in combination with snoring. METHODS AND INTENTION: In 40 patients with OSA (AHI > 15/h) simultaneous polysomnographic recordings were performed amongst long-term respiratory sound monitoring using the LEOSound monitor. Patients' average age was 57 ±â€Š11 years. Average weight was 100 ±â€Š19 kg by a mean body  mass  index (BMI) of 33 ±â€Š7 kg/m2. 12 out of 40 recordings had to be rejected for further analysis because of artifacts. Snoring recorded by polysomnography was compared with snoring monitored by LEOSound. RESULTS: 3778 obstructive apnea episodes were monitored. LEOSound identified snoring in 1921 (51,0 %), polysomnography in 2229 (58,8 %) obstructive apneas. Only in one patient there was a higher difference in snoring episodes between PSG and LEOSound. DISCUSSION: In nearly 60 % of obstructive apnea events we found snoring during apnea-terminating hyperpnoea. LEOSound is a good diagnostic tool to monitor snoring. It is necessary to clarify why only 60 % of all obstructive events/hyperpnoea develop snoring. From a pathophysiological point of view opening of collapsed upper airway should lead in a very high percentage to turbulences in airstream and committed snoring.

[Apnea Detection by Means of Respiratory Sound Recordings and Polysomnography - A Comparative Study]. / Ein Vergleich der Apnoeerkennung bei Patienten mit obstruktiver Schlafapnoe (OSA) anhand von Atemgeräuschaufzeichnungen und Polysomnografie.

Introduction In this study, recognition of apnoeas by means of polysomnography (PSG) and nocturnal respiratory sound recordings in patients with obstructive sleep apnoea (OSA) was analyzed and compared. Methods In 45 patients with OSA requiring treatment (AHI > 15/h), concomitant polysomnographic recordings and long term respiratory sound recordings by means of LEOSound were performed. Patients' average age was 58 ±â€Š12 years (mean ± standard deviation), average BMI was 33 ±â€Š7 kg/m2. Audio-visual apnoea detection by LEOSound was compared to polysomnographic apnoea detection. Increased artifact rate due to dislocation of microphones led to rejection of 11 out of 45 recordings for detailed analysis. Results Comparison of apnea detection by audio-visual analysis and polysomnography yielded a median of 164 apneas for LEOSound recordings and 158 apneas for PSG. Median apnoea index (AI) was calculated to be 20/h for respiratory sounds recording and 21/h for PSG. The correlation of apnea indices from acoustic long term registration and PSG was 0.939 (p < 0.001). Discussion Acoustic long term registration of primary and secondary respiratory sounds is also capable to recognize apnoeas. Exact differentiation between apnoeas and hypopnoeas is only possible in a limited fashion.

[Obstructive sleep apnea in neurological diseases: specially as a risk factor for stroke]. / Obstruktive Schlafapnoe bei neurologischen Erkrankungen: Speziell als Risikofaktor für Schlaganfall.

Neurological diseases are frequently associated with sleep-related breathing disorders. In contrast patients with obstructive sleep apnea (OSA) suffer more often from cerebrovascular and cardiovascular diseases. Epidemiological studies have shown that OSA is common among patients with stroke, arterial hypertension or cardiovascular disease. In particular apnea-associated arterial hypertension, atrial fibrillation, activation of the sympathetic nervous system, recurrent hypoxemia and vascular inflammatory response should be considered as risk factors for the vascular system. Early diagnosis and treatment of sleep-related breathing disorders in neurological diseases are required to reduce the risk of subsequent cerebrovascular and cardiovascular diseases.

A prospective polysomnographic study on the evolution of complex sleep apnoea.

Complex sleep apnoea (CompSA) may be observed following continuous positive airway pressure (CPAP) treatment. In a prospective study, 675 obstructive sleep apnoea patients (mean age 55.9 yrs; 13.9% female) participated. Full-night polysomnography was performed at diagnosis, during the first night with stable CPAP and after 3 months of CPAP. 12.2% (82 out of 675 patients) had initial CompSA. 28 of those were lost to follow-up. Only 14 out of the remaining 54 patients continued to satisfy criteria for CompSA at follow-up. 16 out of 382 patients not initially diagnosed with CompSA exhibited novel CompSA after 3 months. 30 (6.9%) out of 436 patients had follow-up CompSA. Individuals with CompSA were 5 yrs older and 40% had coronary artery disease. At diagnosis, they had similar sleep quality but more central and mixed apnoeas. On the first CPAP night and at follow-up, sleep quality was impaired (more wakefulness after sleep onset) for patients with CompSA. Sleepiness was improved with CPAP, and was similar for patients with or without CompSA at diagnosis and follow-up. CompSA is not stable over time and is mainly observed in predisposed patients on nights with impaired sleep quality. It remains unclear to what extent sleep impairment is cause or effect of CompSA.

[Measuring sleep duration and sleep quality]. / Messung von Schlafdauer und Schlafqualität.

Restorative functions of sleep are of special interest for sleep medicine. For the assessment of these restorative functions, various parameters are taken into account, among which sleep duration and sleep quality play the most important roles. Both terms are essential for sleep perception, expressing the subjective satisfaction of the individual with the time spent asleep. In recent decades, sleep medicine and sleep research have developed methods for the assessment of both objective and subjective dimensions of sleep. Among subjective methods, taking of the medical history focusing on the patient's sleep is important. Standardized and validated questionnaires play a supportive role. Objective methods are, for example, estimation of the sleep-wake cycle by means of actigraphy and polygraphy. Especially in multimorbid patients, polysomnography is still the gold standard method for diagnostics. An important approach during recent years is shifting from bothering overnight examinations into less disturbing procedures for patients that include performing ambulatory, outpatient examinations in the patients' home rather than inpatient surveillance within sleep centers.

[Daytime sleepiness in patients with Obstructive Sleep Apnoea (OSA) - pathogenetic factors]. / Tagesschläfrigkeit bei obstruktiver Schlafapnoe (OSA) - pathogenetische Faktoren.

Excessive daytime sleepiness (EDS) is one of the most frequent symptoms in patients with obstructive sleep apnoea (OSA). EDS can lead to substantial impairments in quality of life and is a major cause of fatal accidents. However, not all patients with OSA develop EDS. The aim of this paper is to review the current literature to identify factors having an impact on sleepiness in patients with OSA. Interestingly, a substantial heterogeneity of the results was found. Summarising these results, causes of EDS in patients with OSA are multifactorial. Severity of obesity and breathing disorders (apnoea/hypopnoea index) seem to be the most important predictors. Continuous positive airway pressure therapy significantly reduces sleepiness in patients with OSA.

[Chronic pulmonary diseases: point of view of partners and their assessments with regard to the effects of lung sports]. / Chronische Lungenerkrankung: Sicht der Partner und deren Einschätzung bezüglich der Effekte von Lungensport.

BACKGROUND: Chronic diseases of the respiratory organs have, besides restrictions of lung function, also physical, mental and social consequences. The chronic disease impacts negatively not only the patient's own quality of life but also that of his/her partner and/or relative. As treatment modalities, besides drug therapy, above all outpatient rehabilitation measures have proved to be effective. In this pilot study we sought answers to three questions: (i) How is the quality of life of the patient's partner and/or relative influenced by the disease? How does the partner/relative assess the effect of the disease on the chronically ill patient? How does the partner/relative assess the effect of lung sports on the chronically ill patient? METHODS: A specially conceived questionnaire was given to the partners/relatives of 25 patients with chronic pulmonary diseases. The patients, 23 with chronic obstructive pulmonary disease and 2 with pulmonary fibrosis, have been participating in lung sports once a week for more than three years. The average age of the patients was 67 years. RESULTS: The patients' illness also negatively influenced the quality of life of the partner to a considerable extent. The impact of the patients' pulmonary disease on the healthy partner was assessed as being rather moderate. Restrictions of social life were essentially influenced by the amount of assistance required by the pulmonary patient. The therapeutic effects of lung sports on the well-being of the patient were aways considered to be positive by the respective partner/relatives. CONCLUSION: A chronic pulmonary illness also has a negative influence on the partner/relative's quality of life. The necessity for extensive assistance in daily life is accompanied by a considerable negative impact on the partner's quality of life. According to the opinion of the partner/relative, lung sports have positive effects in all of the chronically ill patient's fields of life.

[Long-term opioid therapy and respiratory insufficiency during sleep]. / Chronische Morphintherapie und respiratorische Insuffizienz im Schlaf.

An increasing proportion of the patients with chronic pain are being treated with opioids on a long-term basis. There are indications that the causes of hypersomnia in patients under chronic opioid therapy are primarily related to breathing disorders during sleep. Hence, we compared the polysomnographies of three hypersomnic patients receiving long-term opioid therapy before and during nocturnal non-invasive ventilatory therapy. Significant findings were a central breathing pattern accompanied by reduced deep and REM sleep. On applying non-invasive ventilatory therapy, there was a significant improvement of respiratory status with an increase of deep sleep as well as a moderate decrease in hypersomnia. In patients under chronic opioid therapy with hypersomnia, the presence of central breathing disorders should be considered.

Does short-term treatment with modafinil affect blood pressure in patients with obstructive sleep apnea?

OBJECTIVE: To investigate the effects of modafinil, a central nonamphetamine awakening substance, on blood pressure and heart rate in hypersomnolent patients with obstructive sleep apnea. DESIGN: This double-blind, randomized, placebo-controlled crossover trial was performed over 2 days and 3 nights in a single-center study of hospitalized patients from a referred care center. Twenty-six otherwise healthy men (age range, 30 to 60 years) with mild to moderate obstructive sleep apnea were recruited by the outpatient department of the Marburg University Sleep Laboratory. Patients were given 200 mg oral modafinil in the morning and 100 mg at midday. Placebo was given in the same manner in a crossover design. Mean arterial (radial) blood pressure was monitored continuously during nocturnal sleep and during a series of standardized daytime physical and psychologic performance tests. RESULTS: The difference in the main end point between the treatment with modafinil and placebo was 1.17+/-0.83 (mean +/- SE) mm Hg (95% confidence interval: -0.56 to 2.91 mm Hg). The maximal differences in blood pressure values occurred under loaded conditions (systolic blood pressure, ergometry: 5.62+/-1.13 mm Hg; mental stress test: 6.19+/-1.33 mm Hg). CONCLUSION: Short-term administration of modafinil did not elicit a significant response with regard to the main end point. However, cardiovascular effects during mental and physical load were observed. Longterm studies that include subjects with hypertension are necessary to investigate the clinical relevance of the cardiovascular effects of modafinil.

The effect of triazolam and flunitrazepam--two benzodiazepines with different half-lives--on breathing during sleep.

We performed a double-blind single-dose placebo/hypnotics crossover study randomized within groups to test the potential problems that a group of normal subjects, including subjects who snore, may face using hypnotic medications. Two benzodiazepine hypnotics--triazolam, 0.25 mg, and flunitrazepam, 2 mg tablets--were considered. Subjects were monitored with nocturnal polysomnography, including esophageal pressure (Pes) monitoring as a measure of respiratory efforts, and were given daytime performance tests. Results were analyzed for the total nocturnal sleep period and also by thirds of the night in consideration of the different half-lives of the studied drugs. Three specific respiratory variables were evaluated: mean breathing frequency for selected unit of time, "Delta Pes" (esophageal pressure at peak end-expiration minus Pes at peak end-inspiration) expressed in cm H2O, and the ratio of Delta Pes/Delta TI (inspiratory time), taken as an index of respiratory drive calculated for each respiratory cycle. There was no significant increase in either the respiratory disturbance index or the oxygen desaturation index (number of drops in arterial oxygen saturation of 4% or more per hour of sleep, as measured by pulse oximetry). There was a significant increase in mean breathing frequency with flunitrazepam compared with placebo, as well as a significantly larger percentage of time during sleep with Delta Pes above 10 cm H2O (taken as a cutoff point for normal respiratory effort) with both triazolam and flunitrazepam compared with placebo. These respiratory changes, even if significant, were minor but may become a liability in association with specific abnormalities.

Arterial hypertension and sleep apnoea: effect of the angiotensin-converting enzyme (ACE) inhibitor cilazapril on continuously measured blood pressure during sleep and wakefulness.

Male patients with arterial hypertension and obstructive sleep-related breathing disorders (mean age 50 y, Body Mass Index (BMI) 32.4 kg m-2, Respiratory Disturbance Index (RDI) 47.2 and systolic/diastolic blood pressure (SBD/DBD) 162/103 mmHg) were examined before and after 8 days of treatment with the long-acting angiotensin-converting-enzyme (ACE) inhibitor cilazapril 2.5 mg vs. placebo in a double-blind design with parallel groups. Cardiorespiratory polysomnography was carried out at night; during daytime wakefulness patients submitted to examinations of physical and mental exertion. Cilazapril reduced the mean pressure during the entire examination period (day and night) by 9.55 (SD +/- 7.13) mmHg, compared to 4.57 (SD +/- 7.20) mmHg for placebo (P < 0.006), independently from systematic changes of heart rate (x = -3.3 and -3.5 bpm, respectively). During REM sleep, mean arterial pressure was significantly reduced by 8.63 (SD +/- 10.1) mmHg, compared to a reduction on placebo of 3.17 (SD 9.6) mmHg (P = 0.023). Under psychometric strain, the mean arterial pressure was reduced by 15.31 (SD +/- 8.7) mmHg with cilazapril; under placebo medication by 6.19 (SD +/- 7.3) mmHg (P < 0.0001). Heart rate was not significantly changed.

Vigilance stages and performance in OSAS patients in a monotonous reaction time task.

OBJECTIVES: To develop improved methods for objective assessment of daytime vigilance. This is important in the diagnosis and therapy control of sleep disorders associated with excessive daytime sleepiness (EDS). METHODS: Twenty-one patients with EDS due to obstructive sleep apnea were recorded during a daytime 90 min reaction time (RT) test in a monotonous situation. Two EEG, two EOG and a submental EMG channel were recorded simultaneously. The recordings were divided into short, stationary segments of variable length (0.5-2 s) and classified into 7 stages using our previously described system, which includes additional stages for drowsiness. RESULTS: The duration of RT was linearly correlated to the vigilance state (P<0.05). The appearance of slow eye movements (SEM) was more consistently related to performance impairment than EEG changes. CONCLUSIONS: Our system can provide a better tracking of vigilance changes than the standardized sleep stage scoring. A 1-2 h test is useful in the assessment of the performance of a subject suffering from EDS. We found that SEMs indicate more sensitive and consistent EDS-related performance impairment than changes in EEG activity.

An animal model for small-diameter arterial grafts.

A rabbit model was developed to study small-diameter arterial grafts. A total of 158 2-mm-diameter polytetrafluoroethylene (PTFE) grafts and 35 autogenous carotid artery (AA) grafts were interposed in the carotid arteries of New Zealand white rabbits. A pilot study of 16 PTFE grafts used to develop operative and anesthetic techniques had a 20% mortality and 38% early (less than 2 day) thrombosis rate. Subsequent to the pilot study 177 grafts were placed and a 92% postoperative survival with 100% AA graft patency and 93% PTFE graft patency at 2 weeks was observed. AA grafts followed beyond 16 weeks continued to have 100% patency, while PTFE grafts began to show increased failure. Closure was found to be due to the development of anastomotic myointimal hyperplasia.

A new method to study blood pressure, heart rate and EEG as a function of reaction time.

A new method is presented to study the relationship between reaction time and blood pressure, heart rate and EEG. The method consists of a simultaneous recording of continuous invasive or non-invasive arterial blood pressure, ECG, EEG, EMG and EOG in a sound-isolated chamber while a monotonous visual reaction time test is running for about 90 minutes. The signals are A/D-converted and analyzed digitally after recording. One second average amplitudes are computed. Systolic, mean and diastolic blood pressure values are calculated, and the EEG is divided into the delta, theta, alpha, sigma and beta frequency bands. The signal amplitudes are averaged in three different reaction time categories, i.e., when the reaction is normal, delayed or missing. Preliminary tests suggest that interesting differences can be observed in the studied variables in different reaction time classes. This method can also be applied to the investigation of autonomic control and to treatment studies.

Combined epidural and general anesthesia in aortic surgery.

The perioperative course of 144 consecutive patients undergoing aortic reconstructive surgery was studied to assess the potential benefit of employing a combined epidural and light general anesthesia technique. A group of 67 patients had general anesthesia alone (GA), while in the group of 77 remaining patients, a combined epidural and general anesthesia (Epi-GA) was employed. The two groups were similar in regards to age, medical risk factors, preoperative assessment of cardiac and pulmonary function, and type of surgical reconstruction. There was no significant difference in the anesthetic, operative time, or operative fluid requirements between the two groups. There was a lower rate pressure product in the Epi-GA group during aortic cross clamping (P less than 0.05). More patients in the GA group required a prolonged ventilatory support (P less than 0.05) and a high parenteral narcotic administration (P less than 0.025) during the first 48 hours. While the mortality rate was similar for the two groups (3.0% for GA group vs 5.2% for Epi-GA group), there was a higher percent of postoperative pulmonary complications observed in the GA group (7.6%) compared to the Epi-GA group (2.6%). By facilitating early extubation and a decreased need for systemic narcotics in the early postoperative period, Epi-GA may be beneficial in the high risk pulmonary patient undergoing aortic reconstruction.

[Nocturnal ventricular arrhythmia in patients with sleep apnea and suspected coronary heart disease]. / Nächtliche ventrikuläre Arrhythmien bei Patienten mit Schlafapnoe und Verdacht auf koronare Herzerkrankung.

BACKGROUND: Patients with sleep apnea and nocturnal brady- and tachyarrhythmia are considered to be patients at especially high risk within the group of all apnea patients. PATIENTS AND METHODS: 13 patients with sleep apnea (apnea-index > 10 events/h), suspected coronary heart disease and known increased frequency of nocturnal premature ventricular contractions (PVC) were studied. Polysomnography, long-term ECG and six-lead ECG were performed. RESULTS: Within the period studied (1.00 to 6.00 o'clock), an average of 47 PVC per hour was recorded (range 4 to 337/h). In two patients 24 episodes of nocturnal myocardial ischemia were observed, but were not accompanied by PVC. Interestingly only 387 of 1371 premature ventricular contractions (28.2%) were associated to apnea/hyperventilation episodes. Arrhythmia occurred mainly during sleep stages I/II and REM (n.s.). There was a tendency towards more frequent PVC with more pronounced oxygen desaturations. CONCLUSION: Patients with coronary heart disease, obstructive sleep apnea and severe hyoxemia are at higher risk of developing nocturnal PVC because reduced hypoxic tolerance of the heart may lead to electrical instability.

ECG signal analysis for the assessment of sleep-disordered breathing and sleep pattern.

The diagnosis of sleep-disordered breathing (SDB) usually relies on the analysis of complex polysomnographic measurements performed in specialized sleep centers. Automatic signal analysis is a promising approach to reduce the diagnostic effort. This paper addresses SDB and sleep assessment solely based on the analysis of a single-channel ECG recorded overnight by a set of signal analysis modules. The methodology of QRS detection, SDB analysis, calculation of ECG-derived respiration curves, and estimation of a sleep pattern is described in detail. SDB analysis detects specific cyclical variations of the heart rate by correlation analysis of a signal pattern and the heart rate curve. It was tested with 35 SDB-annotated ECGs from the Apnea-ECG Database, and achieved a diagnostic accuracy of 80.5%. To estimate sleep pattern, spectral parameters of the heart rate are used as stage classifiers. The reliability of the algorithm was tested with 18 ECGs extracted from visually scored polysomnographies of the SIESTA database; 57.7% of all 30 s epochs were correctly assigned by the algorithm. Although promising, these results underline the need for further testing in larger patient groups with different underlying diseases.