Prognosis of the middle-aged and aged patients with obstructive sleep apnea syndrome

Very low frequency component of heart rate variability as a marker for therapeutic efficacy in patients with obstructive sleep apnea: Preliminary study

BACKGROUND

Although positive airway pressure (PAP) therapy is effective for treating obstructive sleep apnea (OSA), some patients with severe OSA are intolerable to this treatment, which may lead to an increase in the mortality and morbidity of cardiovascular diseases. We investigated the relationship between heart rate variability (HRV) and sleep parameters during natural sleep and treatment of patients with OSA.

MATERIALS AND METHODS

This was the cross-sectional observation study. Patients were 17 males with severe OSA who were unable to accept continuous PAP. Standard polysomnography was performed for two consecutive nights, i.e., during natural sleep and following night with bilevel PAP (BiPAP) treatment. Time-dependent responses of the amplitudes of low frequency (LF), very low frequency (VLF), and high frequency components of HRV were assessed with the technique of complex demodulation.

RESULTS

Apnea-hypopnea index, oxygen desaturation time, and percentage of stage 1 sleep were significantly reduced, whereas the percentages of rapid eye movement and stages 3 + 4 sleep were increased, by BiPAP treatment. Therapy also reduced the amplitudes of VLF and LF components of HRV. Difference in amplitudes of VLF during natural sleep and treatment with BiPAP was significantly correlated with difference in percentages of stage 1 and stages 3 + 4 sleep.

CONCLUSION

Therapy-induced amelioration of OSA and sleep quality was accompanied by decrease in the amplitudes of VLF components of HRV. The VLF component may thus reflect physiological changes in both autonomic activity and sleep structure and serve as an objective marker for therapeutic efficacy in patients with severe OSA.

Poor sleep quality impairs cognitive performance in older adults

The prevalence of insomnia increases with age. Short sleep duration is associated with deficits in cognitive performance. We hypothesized that short sleep duration and sleep quality influence cognitive performance in older adults. The study included 78 adults aged 60 years and over (72.2 ± 5.9 years). Total sleep time and sleep efficiency (total sleep time/time in bed × 100) were calculated using actigraphy. We evaluated cognitive performance with the continuous performance test-identical pairs and the number-back test. Sleep apnea was evaluated overnight with a portable home monitoring system. The accuracy of the 0-back test significantly decreased in participants with total sleep time less than 5 h compared with those with total sleep time greater than 7 h, but there was no significant difference in continuous performance test-identical pairs between the two groups. Participants with sleep efficiency <85% showed a significant decrease in 0- and 1-back test accuracy compared with those with sleep efficiency ≥85%. There were no significant differences in the accuracy of number-back tests and continuous performance test-identical pairs between apnea-hypopnea index ≥15 h(-1) and apnea-hypopnea index <15 h(-1) groups, or among lowest SpO2  ≥ 90%, lowest 80-90%, and lowest SpO2  < 80% groups. Age, total sleep time and sleep efficiency were significantly correlated with accuracy on the 0-back test. Age and sleep efficiency were significantly correlated with accuracy on the 1-back test. Multiple regression analysis revealed that total sleep time was independently correlated with accuracy on the 0-back test, while age was independently correlated with accuracy on the 1-back test. Our findings suggest that sleep duration and sleep quality may play a role in cognitive performance in older adults.

Therapeutic strategies for sleep apnea in hypertension and heart failure

Sleep-disordered breathing (SDB) causes hypoxemia, negative intrathoracic pressure, and frequent arousal, contributing to increased cardiovascular disease mortality and morbidity. Obstructive sleep apnea syndrome (OSAS) is linked to hypertension, ischemic heart disease, and cardiac arrhythmias. Successful continuous positive airway pressure (CPAP) treatment has a beneficial effect on hypertension and improves the survival rate of patients with cardiovascular disease. Thus, long-term compliance with CPAP treatment may result in substantial blood pressure reduction in patients with resistant hypertension suffering from OSAS. Central sleep apnea and Cheyne-Stokes respiration occur in 30-50% of patients with heart failure (HF). Intermittent hypoxemia, nocturnal surges in sympathetic activity, and increased left ventricular preload and afterload due to negative intrathoracic pressure all lead to impaired cardiac function and poor life prognosis. SDB-related HF has been considered the potential therapeutic target. CPAP, nocturnal O2 therapy, and adaptive servoventilation minimize the effects of sleep apnea, thereby improving cardiac function, prognosis, and quality of life. Early diagnosis and treatment of SDB will yield better therapeutic outcomes for hypertension and HF.

Association of insomnia and short sleep duration with atherosclerosis risk in the elderly

BACKGROUND

Short sleep duration is associated with an increased risk of cardiovascular disease and all-cause mortality, although a relationship with atherosclerosis in the elderly remains unclear.

METHODS

Eighty-six volunteers aged ≥65 years (mean, 73.6 ± 4.9 years) were evaluated for insomnia. Total sleep time (TST) and sleep efficiency were measured by actigraphy. Subjective symptoms were assessed with the Pittsburgh Sleep Quality Index (PSQI). Atherosclerosis was evaluated using ultrasonographic measurements of carotid intima-media thickness (IMT).

RESULTS

IMT was significantly greater and sleep efficiency was significantly lower in subjects with TST ≤5 h than those with TST >7 h (1.3 ± 0.5 vs. 0.9 ± 0.3 mm; P = 0.009; 91.0 ± 6.0 vs. 81.6 ± 11.3%, P = 0.03, respectively). IMT was also significantly greater in the insomnia group than the noninsomnia group (1.3 ± 0.5 vs. 1.1 ± 0.4 mm; P = 0.03). IMT was significantly correlated with systolic blood pressure (SBP), diastolic blood pressure (DBP), and TST (SBP: r = 0.49, P < 0.0001; DBP: r = 0.33, P = 0.0021; TST: r = -0.28, P = 0.010). Multiple regression analysis revealed that SBP, TST, and the PSQI were significant contributing factors for increased IMT (SBP: coefficient β = 0.56, P = 0.0001; TST: coefficient β = -0.32, P = 0.005; PSQI: coefficient β = 0.22, P = 0.05).

CONCLUSIONS

High blood pressure, short sleep duration (≤5 h), poor sleep, and insomnia were associated with atherosclerosis risk leading to cardiovascular disease in the elderly.

Lack of association of the APOE epsilon 4 allele with the risk of obstructive sleep apnea: meta-analysis and meta-regression

STUDY OBJECTIVES

Reports on the association of polymorphisms in the gene encoding apolipoprotein E (APOE)--a vital macromolecule in cholesterol metabolism--with obstructive sleep apnea (OSA) have provided conflicting results. Our objective was to meta-analytically synthesize the existing evidence for the association of the APOE epsilon4 allele with the risk of OSA.

DESIGN

Random effects meta-analysis and meta-regression.

SETTING

Genetic epidemiological studies reporting the association of APOE epsilon4 allele with OSA susceptibility.

PATIENTS OR PARTICIPANTS

Synthesis of APOE epsilon4 allele data from 6,508 subjects including 1,901 cases of OSA and 4,607 controls.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Eight studies were included in the random effects meta-analysis; the summary effect size measured as odds ratio (OR) for association of the APOE epsilon4 allele with the risk of OSA was found to be 1.13 (95% confidence interval 0.86-1.47). There was a statistically significant heterogeneity (I2 = 72%, P = 0.001) across study results that was not explained by the mean age, proportion of males, or the proportion possessing the APOE epsilon4 allele or when grouped based on the geographic location of the study.

CONCLUSIONS

The hypothesis that the APOE epsilon4 allele may be causally associated with OSA cannot be supported on the basis of published literature.

The MMPI-2 Symptom Validity Scale (FBS) Not Influenced by Medical Impairment: A Large Sleep Center Investigation

The Symptom Validity Scale (Minnesota Multiphasic Personality Inventory—2—FBS [MMPI-2-FBS]) is a standard MMPI-2 validity scale measuring overstatement of somatic distress and subjective disability. Some critics assert the MMPI-2-FBS misclassifies too many medically impaired persons as malingering symptoms. This study tests the assertion of malingering misclassification with a large sample of 345 medical inpatients undergoing sleep studies that standardly included MMPI-2 testing. The variables included standard MMPI-2 validity scales (Lie Scale [L], Infrequency Scale [F], K-Correction [K]; FBS), objective medical data (e.g., body mass index, pulse oximetry), and polysomnographic scores (e.g., apnea/hypopnea index). The results showed the FBS had no substantial or unique association with medical/sleep variables, produced false positive rates <20% (median = 9, range = 4-11), and male inpatients showed marginally higher failure rates than females. The MMPI-2-FBS appears to have acceptable specificity, because it did not misclassify as biased responders those medical patients with sleep problems, male or female, with primary gain only (reducing sickness). Medical impairment does not appear to be a major influence on deviant MMPI-2-FBS scores.

Aortic pressure augmentation as a marker of cardiovascular risk in obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is associated with increases in cardiovascular morbidity and mortality. Vascular changes in individuals with OSAS have not been fully elucidated, however. The possible impact of OSAS on the extent of aortic pressure augmentation (AG), an indicator of cardiovascular risk, was investigated. Forty-five consecutive male patients aged 35 to 78 years (56.0+/-9.6 years) who were referred to the sleep clinic of Nagoya University Hospital for screening and treatment of OSAS and 71 age-matched healthy men were enrolled in the study. AG was derived from the pressure waveform measured at the radial artery by applanation tonometry. The number of apnea and hypopnea episodes per hour (apnea-hypopnea index [AHI]) was determined by standard polysomnography. AG was significantly greater in OSAS patients than in controls (9.0+/-4.1 vs. 6.4+/-3.4 mmHg, p<0.001), and it was significantly reduced in 19 OSAS patients treated with continuous positive airway pressure. AG was also significantly correlated with the AHI (r=0.562, p<0.001) and age (r=0.356, p=0.016) but not with the serum concentrations of low and high density lipoprotein-cholesterol, triglyceride, or glycosylated hemoglobin. Stepwise multiple regression analysis revealed that the AHI was the most significant contributing factor to the increased AG in OSAS patients (beta=0.109, r=0.530, p<0.001). OSAS may thus have an adverse effect on vascular function that can be ameliorated by appropriate treatment.

The role of malocclusion in non-obese patients with obstructive sleep apnea syndrome

OBJECTIVE

The maxillofacial characteristics of patients with obstructive sleep apnea syndrome (OSAS) have previously been analyzed using standard cephalometric analysis. Malocclusion influences the occurrence of sleep apnea, but the pathology of malocclusion in OSAS has not yet been fully investigated. Therefore, we investigated malocclusion in patients with OSAS using cephalometric and dental analysis.

METHODS

Cephalometric and dental analyses were performed to evaluate malocclusion in 97 male patients with OSAS (49.7+/-11.7 years). The number of apnea and hypopnea episodes per hour (apnea-hypopnea index: AHI) was determined by standard polysomnography.

RESULTS

The overall prevalence of severe overjet (the horizontal distance between the upper and lower incisors of >or=6 mm) was 43.3%. AHI was significantly correlated with body mass index (BMI) in obese OSAS patients (r=0.385, p=0.010), whereas it was significantly correlated with overjet in non-obese OSAS patients (BMI<25 kg/m2) (r=0.313, p=0.022). Multiple regression analysis revealed that BMI was the significant factor contributing to increased AHI in all patients, and overjet was in non-obese OSAS patients. There were no significant differences between non-obese and obese OSAS patients in the angle of protrusion of the superior alveolar base (SNA) or in the angle of protrusion between the superior and inferior alveolar bases (ANB). The angle of protrusion of the inferior alveolar base (SNB) was significantly smaller in non-obese than in obese OSAS patients.

CONCLUSION

We have shown that overjet was associated with the severity of OSAS in non-obese patients. Our findings suggest that malocclusion may play an important role in the development of sleep apnea/hypopnea.

Assessment of continuous positive airway pressure treatment in obstructive sleep apnea syndrome using 24-hour urinary catecholamines

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is related to diurnal sympathetic hyperactivity and increased blood pressure, both factors that are likely to lead to the development of cardiovascular disease.

HYPOTHESIS

The study investigated whether 24-h urinary catecholamines would reflect the effect of obstructive sleep apnea on autonomic activity.

METHODS

Standard polysomnography was performed in 17 patients with OSAS (age 53.7 +/- 13.5 years, mean +/- standard deviation). The number of apnea/hypopnea episodes per hour of sleep (apnea/hypopnea index [AHI]); number of oxygen desaturation episodes per hour (desaturation index [DSI]); arousals per hour (arousal index); lowest oxygen saturation (lowest SpO2); and percentages of stages 1, 2, 3/4, and rapid eye movement sleep (% stage 1, -2, and -3/4, and % REM, respectively) were measured. Overnight continuous positive airway pressure (CPAP) titration was performed the night after the baseline sleep measurements had been taken. Twenty-four-hour urinary adrenaline and noradrenaline were also examined.

RESULTS

During the CPAP treatment, both 24-h urinary adrenaline and noradrenaline were significantly lower compared with natural sleep. Continuous positive airway pressure significantly decreased the AHI, DSI, % stage 1, and arousal index and significantly increased the lowest SpO2. There were no significant differences in % stage 2, % stage 3/4, and % REM between before and during CPAP treatment. Multiple analysis of covariance tests revealed that lowest SpO2 was the most important factor for increasing 24-h urinary noradrenaline levels (F = 4.75, p = 0.048).

CONCLUSIONS

One night CPAP treatment could improve autonomic dysfunction. The assessment of 24-h urinary noradrenaline would provide important information for evaluating the effect of CPAP treatment.

Amelioration of vascular endothelial dysfunction in obstructive sleep apnea syndrome by nasal continuous positive airway pressure--possible involvement of nitric oxide and asymmetric NG, NG-dimethylarginine

BACKGROUND

Asymmetric NG,NG-dimethylarginine (ADMA) is an endogenous inhibitor of endothelial nitric oxide (NO) synthase and its plasma concentration is elevated in patients with cardiovascular risk factors, including hyperlipidemia, hypertension, diabetes, and hyperhomocysteinemia. Obstructive sleep apnea syndrome (OSAS) has been attracting attention as a risk factor for cardiovascular disorders because it often accompanies hypertension, obesity, glucose impairment, and dyslipidemia, all of which are factors in metabolic syndrome and risk factors for cardiovascular disease.

METHODS AND RESULTS

In the present study, flow-mediated vasodilatation (FMD) of the brachial artery and plasma concentrations of ADMA were measured before and after nasal continuous positive airway pressure (nCPAP) therapy, which abrogates apnea, in 10 male patients aged 36-69 years old, who were given a diagnosis of OSAS by polysomnography. The percent FMD (%FMD) improved significantly from 3.3+/-0.3% to 5.8+/-0.4% (p<0.01) and 6.6+/-0.3% (p<0.01), before, 1 week, and 4 weeks after nCPAP, respectively. At the same time, the plasma NOx concentrations, metabolites of NO, tended to increase, but the plasma ADMA concentration decreased inversely to %FMD and NOx. A negative correlation between %FMD and plasma ADMA concentration, and a positive correlation between %FMD and plasma NOx concentrations were observed.

CONCLUSION

Nasal CPAP improves endothelial function, in part by the decreasing ADMA concentration, thereby potentiating NO production.

Evidence-based medicine in sleep apnea surgery

Since the first description of sleep apnea as a clinical entity, the understanding of it within the medical community has increased significantly. Much research has explored the causes, assessment, and treatment of this disease. This research has resulted in a variety of tools for assessment and approaches to treatment. As research progresses, new data have shed light on the strengths of traditional approaches and their limitations. This article gives background for current approaches and charts a potential future course for sleep apnea assessment and treatment.

Severe obstructive sleep apnea is associated with left ventricular diastolic dysfunction

INTRODUCTION

Hypertension is common in patients with obstructive sleep apnea (OSA). However, the effect of OSA on ventricular function, especially diastolic function, is not clear. Therefore, we have assessed the prevalence of diastolic dysfunction in patients with OSA and the relationship between diastolic parameters and severity of OSA.

METHODS

Sixty-eight consecutive patients with OSA confirmed by polysomnography underwent echocardiography. Diastolic function of the left ventricle was determined by transmitral valve pulse-wave Doppler echocardiography. Various baseline characteristics, severity of OSA, and echocardiographic parameters were compared between patients with and without diastolic dysfunction.

RESULTS

There were 61 male and 7 female patients with a mean age of 48.1 +/- 11.1 years, body mass index of 28.5 +/- 4.3 kg/m(2), and apnea/hypopnea index (AHI) of 44.3 +/- 23.2/h (mean +/- SD). An abnormal relaxation pattern (ARP) in diastole was noted in 25 patients (36.8%). Older age (52.7 +/- 8.9 years vs 45.1 +/- 11.3 years, p = 0.005), hypertension (56% vs 20%, p = 0.002), and a lower minimum pulse oximetric saturation (SpO(2)) during sleep (70.5 +/- 17.9% vs 78.8 +/- 12.9%, respectively; p = 0.049) were more common in patients with ARP. By multivariate analysis, minimum SpO(2) < 70% was an independent predictor of ARP (odds ratio, 4.34; 95% confidence interval, 1.23 to 15.25; p = 0.02) irrespective of age and hypertension. Patients with AHI > or = 40/h had significantly longer isovolumic relaxation times than those with AHI < 40/h (106 +/- 19 ms vs 93 +/- 17 ms, respectively; p = 0.005).

CONCLUSION

Diastolic dysfunction with ARP was common in patients with OSA. More severe sleep apnea was associated with a higher degree of left ventricular diastolic dysfunction in this study.

Sleep-disordered breathing and coronary artery disease: long-term prognosis

The evidence linking sleep-disordered breathing to increased mortality and cardiovascular morbidity has been conflicting and inconclusive. We hypothesized that a potential adverse effect of disordered breathing would be more obvious in patients with established vascular disease. In a prospective cohort study 408 patients aged 70 yr or younger with verified coronary disease were followed for a median period of 5.1 yr. An apnea-hypopnea index (AHI) of > or = 10 and an oxygen desaturation index (ODI) of > or = 5 were used as the diagnostic criteria for sleep-disordered breathing. The primary end point was a composite of death, cerebrovascular events, and myocardial infarction. There was a 70% relative increase and a 10.7% absolute increase in the primary composite end point in patients with disordered breathing defined as an ODI of > or = 5 (risk ratio 1.70, 95% confidence interval [CI] 1.15-2.52, p = 0.008). Similarly, patients with an AHI of > or = 10 had a 62% relative increase and a 10.1% absolute increase in the composite endpoint (risk ratio 1.62, 95% CI 1.09-2.41, p = 0.017). An ODI of > or = 5 and an AHI of > or = 10 were both independently associated with cerebrovascular events (hazard ratio 2.62, 95% CI 1.26-5.46, p = 0.01, and hazard ratio 2.98, 95% CI 1.43-6.20, p = 0.004, respectively). We conclude that sleep-disordered breathing in patients with coronary artery disease is associated with a worse long-term prognosis and has an independent association with cerebrovascular events.

Knowledge of sleep apnea in a sample grouping of primary care physicians

The purpose of this pilot study was to examine four groups of primary care physicians' knowledge of sleep apnea.

METHODS

Using a 36-item questionnaire, we investigated how cognizant primary care physicians in Ontario, Canada, were of sleep apnea and its different symptoms. The questions covered incidence, diagnosis, treatment, and medical and social ramifications of sleep apnea. Sleep apnea surveys were administered to small groups of primary care physicians attending educational conferences or were distributed by mail to physicians who had previously referred patients to the sleep clinic.

RESULTS

A total of 151 physicians responded to the survey. An overall average score of 69% was obtained on the questionnaire.

CONCLUSIONS

This score suggests that the physicians sampled in this pilot study are relatively under-informed about the clinical features and medical and social ramifications associated with sleep apnea.

Influence of movement arousal on circadian rhythm of blood pressure in obstructive sleep apnea syndrome

OBJECTIVE

To investigate the hypothesis that repeated arousals at the termination of apnea/hypopnea in obstructive sleep apnea syndrome (OSAS) are related to abnormal circadian rhythm of blood pressure (BP).

DESIGN AND METHODS

We performed polysomnography (PSG) with pulse oximetry in 26 middle-aged patients with OSAS aged 42-58 years (mean age 51.8 years). The intensity of arousal on PSG was graded into two levels: grade 1 (EEG arousal, EA), an abrupt shift in EEG frequency, and grade 2 (movement arousal, MA), EEG arousal with an increase in electromyogram activity lasting at least 3 s. The number of apnea/hypopneas per hour (apnea/hypopnea index, AHI), and length of time during which nocturnal oxygen saturation decreased below 90% (oxygen desaturation time, ODT) were also evaluated. Percentage EA and %MA were assessed by the ratio of the number of apneas and hypopneas with EA or MA to the number of apneas and hypopneas in total. The 24 h systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured noninvasively. Multiple regression analysis was performed among AHI, ODT, %EA and %MA or among age, body mass index and %MA.

RESULTS

The %MA was the most significant factor contributing to the elevated 24 h SBP (r= 0.46, P< 0.05); oxygen desaturation (r= 0.44, P< 0.05) was the next most important contributing factor. The level and pattern of 24 h BP differed significantly between the patients with %MA 85% and %MA < 85% (mean 24 h SBP: 147 +/- 16.8 versus 125 +/- 19.6 mmHg, P< 0.01; mean 24 h DBP: 97.5 +/- 14.3 versus 85.6 +/- 14.6 mmHg, P< 0.01), and also differed between those with severe OSAS, i.e. ODT > or = 130 min, and mild to moderate OSAS, i.e. ODT < 130 min, (mean 24 h SBP: 149 +/- 15.8 versus 132 +/- 20.6 mmHg, P < 0.01; mean 24 h DBP: 100 +/- 14.1 versus 87.4 +/- 14.0 mmHg, P < 0.01).

CONCLUSION

Our findings suggest that MA and oxygen desaturation in OSAS make an important contribution to abnormal circadian rhythm of BP. We conclude that repeated end-apneic arousal and/or hypoxic asphyxia and the subsequent sleep fragmentation may contibute to nocturnal and diurnal elevation of BP.

Clinical presentations of obstructive sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is a common but still underrecognized disorder. It affects 2% to 4% of middle-aged adults, a significant proportion of whom are female. The spectrum of clinical presentations of OSAS and their severity is variable, ranging from neurocognitive complaints to cardiorespiratory failure. OSAS has a significant impact on quality of life, cardiovascular morbidity, and mortality. Its major sequelae include daytime somnolence and its consequences (motor vehicle accidents, poor work performance, disrupted social interactions), systemic and pulmonary hypertension, and ischemic heart disease. Treatment of OSAS results in improvement in symptoms, quality of life, and blood pressure control, and may improve mortality. An expansion of our understanding of this condition has resulted in increased awareness of its consequences, but the recognition of OSAS in clinical practice is still delayed. Identification of these patients in clinical practice requires attention to risk factors (history of snoring and witnessed apneas, obesity, increased neck circumference, hypertension, family history) and careful examination of the upper airway. Clinical impression alone, however, has poor (50% to 60%) sensitivity and specificity (63% to 70%) and the diagnosis is usually obtained on polysomnography. Physicians and other health care professionals need to be aware of the progress made in this area and recognize the necessity for prompt evaluation and treatment of these patients.