Snoring and systemic hypertension--an epidemiological study

The Impact of Intermittent Hypoxia on Metabolism and Cognition

Intermittent hypoxia (IH), one of the primary pathologies of sleep apnea syndrome (SAS), exposes cells throughout the body to repeated cycles of hypoxia/normoxia that result in oxidative stress and systemic inflammation. Since SAS is epidemiologically strongly correlated with type 2 diabetes/insulin resistance, obesity, hypertension, and dyslipidemia included in metabolic syndrome, the effects of IH on gene expression in the corresponding cells of each organ have been studied intensively to clarify the molecular mechanism of the association between SAS and metabolic syndrome. Dementia has recently been recognized as a serious health problem due to its increasing incidence, and a large body of evidence has shown its strong correlation with SAS and metabolic disorders. In this narrative review, we first outline the effects of IH on the expression of genes related to metabolism in neuronal cells, pancreatic β cells, hepatocytes, adipocytes, myocytes, and renal cells (mainly based on the results of our experiments). Next, we discuss the literature regarding the mechanisms by which metabolic disorders and IH develop dementia to understand how IH directly and indirectly leads to the development of dementia.

Intermittent Hypoxia Increased the Expression of DBH and PNMT in Neuroblastoma Cells via MicroRNA-375-Mediated Mechanism

Sleep apnea syndrome (SAS), characterized by recurrent episodes of oxygen desaturation and reoxygenation (intermittent hypoxia (IH)), is a risk factor for hypertension and insulin resistance. We report a correlation between IH and insulin resistance/diabetes. However, the reason why hypertension is induced by IH is elusive. Here, we investigated the effect of IH on the expression of catecholamine-metabolizing enzymes using an in vitro IH system. Human and mouse neuroblastoma cells (NB-1 and Neuro-2a) were exposed to IH or normoxia for 24 h. Real-time RT-PCR revealed that IH significantly increased the mRNA levels of dopamine β-hydroxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT) in both NB-1 and Neuro-2a. Western blot showed that the expression of DBH and PNMT in the NB-1 cells was significantly increased by IH. Reporter assays revealed that promoter activities of DBH and PNMT were not increased by IH. The miR-375 level of IH-treated cells was significantly decreased relative to that of normoxia-treated cells. The IH-induced up-regulation of DBH and PNMT was abolished by the introduction of the miR-375 mimic, but not by the control RNA. These results indicate that IH stress increases levels of DBH and PNMT via the inhibition of miR-375-mediated mRNA degradation, potentially playing a role in the emergence of hypertension in SAS patients.

Association Between Self-Reported Snoring and Metabolic Syndrome: A Systematic Review and Meta-Analysis

Background: Snoring is a common condition. Previous studies have reported the relationships between snoring and metabolic syndrome (MetS) and/or its five components: hypertension, hyperglycemia, low-high density lipoprotein (low-HDL), high-triglyceride level, and abdominal obesity. However, conclusions have been inconsistent, and there has been no comprehensive summary on this. Therefore, we performed a systematic review on the relationships between snoring and MetS, including each of MetS' components.

Methods: A systematic review and a meta-analysis were conducted following the Meta-analysis of Observational Studies in Epidemiology group and Preferred Reporting Items for Systematic Reviews and Meta-analysis guidelines. Electronic databases including PubMed, Embase, and the Cochrane Library were searched for publications from inception to 15 July 2020. The inverse-variance weighted method was used in the meta-analysis to calculate the pooled odds ratios (ORs) and their 95% confidence intervals (CIs) to determine the association between snoring and MetS (and its components) through a fixed or random effect model. A restricted cubic spline regression model and the linear regression model were used in a two-stage dose–response meta-analysis to evaluate the non-linear and the linear trends between snoring frequency and MetS and its components.

Results: A total of 40 studies with 966,652 participants were included in this study. The pooled ORs between snoring and MetS and its components, hypertension, hyperglycemia, low-HDL, high-triglyceride level, and abdominal obesity, were 1.61 (95% CI, 1.43–1.78), 1.23 (95% CI, 1.15–1.31), 1.05 (95% CI, 1.04–1.07), 1.09 (95% CI, 1.00–1.18), 1.08 (95% CI, 1.00–1.17), and 1.75 (95% CI, 1.46–2.05), respectively. Non-linear trends were detected in the five associations except for low-HDL. A linear trend was detected in the association of snoring with hypertension, hyperglycemia, low-HDL, or abdominal obesity, with ORs of 1.07 (95% CI, 1.01–1.13), 1.05 (95% CI, 1.02–1.08), 1.03 (95% CI, 1.02–1.04), and 1.17 (95% CI, 1.16–2.89), respectively.

Conclusion: Snoring was a risk factor of MetS, and a dose–response relationship existed between the two. Timely intervention in identifying snorers can minimize as much as possible the risk of metabolic syndrome in those who snore.

[The problem of obstructive sleep apnea syndrome in asthmatic patients]

Asthma and obstructive sleep apnea syndrome (OSAS) are one of the most common chronic respiratory diseases. These have common risk factors that include obesity, gastroesophageal reflux disease (GERD) and impaired nasal breathing (allergic rhinitis, sinusitis). At the same time, experimental evidence demonstrates common pathophysiological mechanisms of these diseases, such as involvement in the process of the respiratory tract, a systemic inflammatory response, and implementation of neuromechanical reflexes. Thus, there is an obvious synergism between these conditions, which affects symptoms, response to therapy, and prognosis. The available data allow discussion on whether there is a need to identify and treat OSAS in asthmatic patients. By keeping in mind the high incidence of OSAS in patients with severe asthma, it may be suggested that treatment for OSAS can reduce the number of exacerbations, improve the quality of life, and decline the number of obstinate asthma cases. It is very important for general practitioners to assess risk factors, such as body weight, nasal stuffiness, and GERD, and to utilize screening tools for more efficient use of healthcare resources. Considering the known positive effects of CPAP therapy in short-term studies, future investigations should focus on the impact of CPAP therapy on asthma symptoms in the long-term, as well as on the effects of asthma drugs on the course of OSAS.

The effect of obstructive sleep apnea syndrome and snoring severity to intima-media thickening of carotid artery

INTRODUCTION

Intima-media thickening (IMT), which is the early finding of carotid artery atherosclerosis, has been shown to be associated with obstructive sleep apnea syndrome (OSAS). In our study, we aimed to assess prospectively the effect of severity of OSAS and snoring on carotid artery IMT.

METHODS

A total of 102 patients who were admitted to sleep laboratory between May 2011 and May 2012 were included in the study. All patients were examined by polysomnography. Common carotid arteries (CCA) and internal carotid arteries (ICA) were evaluated for IMT by carotid Doppler ultrasonography.

RESULTS

The mean age was 45.9 ± 11.1, with 40 (39.2 %) women and 62 (60.8 %) men. Of 88 OSAS patients who had an apnea-hypopnea index (AHI) of >5, 33 (37.5 %) had mild, 20 (22.7 %) had moderate, and 35 (39.8 %) had severe disease. Fourteen patients who had AHI <5 were designated as the habitual snoring group. IMT was detected in 17 (16.7 %) of all patients. In patients with severe OSAS, CCA walls were thicker (p = 0.040) and IMT ratios were higher (p = 0.019) compared to mild/moderate OSAS patients. In patients with IMT, age, AHI, oxygen desaturation index (ODI), and snoring index were higher compared to patients without IMT (p < 0.05).

CONCLUSION

Carotid artery IMT, which is an early finding of atherosclerosis, was found to be highly correlated with OSAS and snoring severity.

Are sleep symptoms predictors of resistant hypertension in a population-based sample? Findings from the National Health and Nutritional Examination Survey

The aim of this study was to test the association of self-reported sleep symptoms to those identified with severe hypertension in a nationally representative sample of adults. Self-reported and study-measured health and sleep characteristics were collected by the National Health and Nutrition Examination Survey (NHANES) from 2005 to 2008. Of 10,526 individuals with completed sleep surveys participating in the study, the authors identified 379 patients with severe hypertension defined as those treated with ≥ 3 antihypertensive medications including a diuretic; 110 of these had resistant hypertension (RHTN) despite therapy, while 269 were controlled for severe hypertension (CSHTN). Patients with RHTN were more likely to be married, less educated, smoke, and self-report unsatisfactory health and diabetes when compared with patients with CSHTN. Multivariate analyses showed that poorly controlled diabetes (glycated hemoglobin >7%) was the strongest predictor of RHTN (odds ratio, 3.0; 95% confidence interval, 1.2-7.9). Unsatisfactory health (odds ratio, 1.7; 95% confidence interval, 1.7-2.7) was also associated with RHTN. Poorly controlled diabetes and self-reported unsatisfactory heath showed significant association with RHTN. Contrary to expectations, there was no significant association between self-reported snoring/snorting and RHTN, when other factors were examined. The association between poorly controlled diabetes and RHTN warrants further emphasis on strict control of diabetes in these individuals.

Consequências do ronco não-tratado

Em alguns estudos, o ronco tem sido associado com um risco aumentado de hipertensão, doença cardíaca isquêmica e acidente vascular encefálico. Os mecanismos são desconhecidos, mas provavelmente mediados pela apneia obstrutiva do sono. Contudo, a maioria dos roncadores não tem apneia do sono. Se o ronco, por si só, aumenta o risco de doença cardiovascular, isso ainda permanece controverso.

Cardiovascular disease and health-care utilization in snorers: a population survey

STUDY OBJECTIVES

We assessed the prevalence of self-reported snoring in the Hungarian population and established whether different types of snoring are associated with cardiovascular disorders and increased health-care utilization.

DESIGN

Cross-sectional study. Door-to-door survey.

SETTING

Nationally representative population in Hungary.

PARTICIPANTS

Interviews were carried out in the homes of 12,643 persons. We used the Hungarian National Population Register as the sampling frame and implemented a clustered, stratified sampling procedure. The study population represented 0.16% of the population over the age of 18 years according to age, sex, and 150 subregions of the country.

INTERVENTIONS

Not applicable.

MEASUREMENTS AND RESULTS

Thirty-seven percent of men and 21% of women reported loud snoring with breathing pauses. Hypertension, myocardial infarction, and stroke were reported by 26%, 3%, and 4% of the respondents, respectively. There was a significant increase in the prevalence of hypertension, myocardial infarction, and stroke in quiet and loud snorers, as compared with nonsnorers. Multivariate analysis showed an association between loud snoring and hypertension (odds ratio [OR]: 1.40, 95% confidence interval [CI]: 1.24-1.58), myocardial infarction (OR: 1.34, CI: 1.04-1.73), and stroke (OR: 1.67, CI: 1.32-2.11) after statistical adjustment for age, sex, body mass index, diabetes, level of education, smoking, and alcohol consumption. Loud snoring was also associated with measures of health-care use in both sexes.

CONCLUSIONS

Snoring is frequent in the Hungarian adult population, and loud snoring with breathing pauses, in contrast with quiet snoring, is associated with an increased risk of cardiovascular disease and increased health-care utilization.

Two year reduction in sleep apnea symptoms and associated diabetes incidence after weight loss in severe obesity

STUDY OBJECTIVES

To evaluate the effect of bariatric surgery on sleep apnea symptoms and obesity-associated morbidity in patients with severe obesity.

DESIGN

Prospective study.

SETTING

University hospitals and community centers in Sweden.

INTERVENTION

We investigated the influence of weight loss surgery (n=1729) on sleep apnea symptoms and obesity-related morbidity using a conservatively treated group (n=1748) as a control.

MEASUREMENTS AND RESULTS

Baseline BMI in surgical group (42.2+/-4.4 kg/m(2)) and control group (40.1+/-4.6 kg/m(2)) changed -9.7+/-5 kg/m(2) and 0+/-3 kg/m(2), respectively, at 2-year follow-up. In the surgery group, there was a marked improvement in all obstructive sleep apnea (OSA) symptoms compared with the control group (P <0.001). Persistence of snoring (21.6 vs 65.5%, adjusted OR 0.14, 95% CI 0.10-0.19) and apnea (27.9 vs 71.3%, adjusted OR 0.16, 95% I 0.10-0.23) were much less in the surgery group compared with controls. Compared with subjects with no observed apnea at follow-up (n=2453), subjects who continued to have or developed observed apnea (n=404) had a higher incidence of diabetes (adjusted OR 2.03, 95% CI 1.19-3.47) and hypertriglyceridemia (adjusted OR 1.86, 95% CI 1.07-3.25) but not hypertension (adjusted OR 1.09, 95% CI 0.65-1.83) or hypercholesterolemia (adjusted OR 0.91, 95% CI 0.53-1.58).

CONCLUSION

Bariatric surgery results in a marked improvement in sleep apnea symptoms at 2 years. Despite adjustment for weight change and baseline central obesity, subjects reporting loss of OSA symptoms had a lower 2-year incidence of diabetes and hypertriglyceridemia. Improvement in OSA in patients losing weight may provide health benefits in addition to weight loss alone.

Prediction of obstructive sleep apnea in patients presenting to a tertiary care center

The objective of this prospective observational clinical study is to derive and validate a diagnostic model for prediction of obstructive sleep apnea (OSA) in subjects presenting with non-sleep-related complaints in a tertiary care center in north India. We included 102 subjects (group I, range 31-70 years) presenting to the hospital with non-sleep-related complaints. None of the subjects had any significant comorbid illness such as respiratory or congestive cardiac failure. All subjects underwent detailed evaluation including polysomnography (PSG). Various parameters were compared between the cases (apnea-hypopnea index, AHI > or =15/h) and controls (AHI <15/h). Using multivariate logistic regression analysis, a diagnostic model for prediction of OSA was derived. Subsequently, using similar selection criteria, 104 subjects (group II, range 32-68 years) were included for validation of the newly derived diagnostic model. Body mass index [BMI; OR (95% CI), 1.14(1.1-1.2)], male gender 5.0(1.4-27.1), relative-reported snoring index (SI) 2.8(1.7-5.0), and choking index (ChI) 8.1(1.4-46.5) were significant, independent predictors of OSA. Diagnostic model was computed as score = [1.61 x (gender)] + [1.01 x (S1)] + [2.09 x (ChI)] + [0.1 x (BMI)] where, gender: 0 = female, 1 = male and SI, ChI, BMI are actual values. The diagnostic model had an area under the receiver operator characteristics curve of 89.6%. A cutoff of 4.3 for the score was associated with sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 91.3, 68.5, 70.5, and 92.3%, respectively. Misclassification rate with the application of the diagnostic model on group II subjects was 13.5% (14/104). Sensitivity, specificity, PPV, and NPV of the model for predicting OSA in this group were 82, 90.7, 89.1, and 84.5%, respectively. BMI, male gender, SI, and ChI are independent predictors of OSA. Diagnostic model derived from these parameters is useful for predicting presence of OSA and screening subjects for PSG.

The veteran population: one at high risk for sleep-disordered breathing

Sleep complaints are very common among the general population and are usually accompanied by significant medical, psychological and social disturbances (Redline S, Strohl K, Otolaryngol Clin North Am, 132:303, 1999). A higher prevalence of sleep complaints has been described in the elderly (Vgontzas AN, Kales A, Annu Rev Med, 50:387-400, 1999). It is manifested by breathing disturbances during sleep, loud snoring, difficulties maintaining sleep, fatigue, daytime sleepiness, mood effects and impairment of daily activities (Lugaresi E, Cirignotta F, Zucconi M et al., Good and poor sleepers: an epidemiological survey of the San Marino population, Raven, New York, pp 1-12, 1983; Kales A, Soldatos CR, Kales JD, Am Fam Physician, 22:101-108, 1980). It has been associated with cardiovascular, endocrine and neurocognitive manifestations. Growing interest in early diagnosis and treatment has been noted in recent years based on emerging knowledge about the potential health consequences when the disease goes untreated (Nanen AM, Dunagan DP, Fleisher A et al., Chest, 121:1741, 2002). The veteran population in the mainland has a higher tendency for obesity, high blood pressure (HBP), sleep disorders and chronic alcohol consumption (Mustafa M, Erokwu N, Ebose I, Strohl K, Sleep Breath, 9:57-63, 2005). The Hispanic veteran population has never been studied in detail for sleep disorders and related conditions. We used previously validated screening tools for sleep disturbance breathing. Two hundred and forty-five questionnaires were administered. We found a higher prevalence of Obstructive Sleep Apnea Hypopnea Syndrome (OSAHS) in our population compared with data from the mainland (USA). The mean age was 64 years (+/-11). Ninety seven per cent were males. The mean body mass index was 25 kg/cm(2); mean Epworth Sleepiness Scale score was 8. Thirty-four per cent met high-risk criteria for sleep apnea, 53% for insomnia, 13% for symptoms suggestive of narcolepsy and 13% for those suggestive of restless leg syndrome. There were high incidences of alcohol consumption (37.6%), diabetes (32.7%), hypercholesterolemia (31.8%), depression (31.8%), hypertension (39.6%) and post-traumatic stress disorder (PTSD) (9.8%).

Snoring and daytime sleepiness as risk factors for hypertension and diabetes in women--a population-based study

The aim of this study was to analyze whether snoring and excessive daytime sleepiness (EDS), the main symptoms of obstructive sleep apnea syndrome (OSAS), are associated with hypertension and diabetes in women. A random sample of 6779 women aged 20-99 years answered questionnaires on sleep disturbances, daytime symptoms and somatic diseases. The women were categorized into four groups: "no EDS or snoring" (reference group), "snoring but no EDS", "EDS but no snoring" and "snoring and EDS". Prevalences of hypertension and diabetes were lowest in the reference group (8.7% and 1.6%, respectively) and highest among women with both snoring and EDS (hypertension: 26.3%, diabetes: 5.8%). In a multivariate model adjusting for age, body mass index, smoking, physical activity and alcohol dependency, "snoring and EDS" was a risk factor for hypertension (adjusted OR 1.82 (95% CI 1.30-2.55)) while isolated snoring or EDS was not. "Snoring and EDS" was more closely related to hypertension among women aged <50 years (adj. OR 3.41 (1.78-6.54) vs. 1.50 (1.02-2.19), P=0.01). For diabetes, both "EDS but no snoring" and "snoring and EDS" were risk factors and the associations were most pronounced in women aged >50 years (adj. OR 2.33 (1.28-4.26) for "EDS but no snoring" and 2.00 (1.05-3.84) for "snoring and EDS"). We conclude that the combination of snoring and EDS is a risk factor for hypertension and diabetes in women. For hypertension, the risk is partly age dependent and, for diabetes, EDS without snoring is a risk factor of similar magnitude. These differences might indicate differences in pathophysiologic mechanisms underlying the association between sleep-disordered breathing and hypertension and diabetes respectively.

QT dispersion in non-apneic simple snoring patients and the effect of surgical therapy on QT dispersion

AIM

Increased QT dispersion in cases of obstructive sleep apnea, which may induce serious arrhythmias, is a well-known process. However, there is little information about the QT dispersion in patients with simple snoring without apnea. We investigated QT dispersion in snoring and the effect of surgical therapy on QT dispersion.

METHODS

One hundred and sixty two patients with simple snoring without apnea were included in this study. Patients had polysomnography and surface electrocardiography (ECG) on the pre-operative 1st week and post-operative 4th week. The patients underwent one of the three surgical procedures, which include uvulopalatopharyngoplasty, laser assisted uvulopalatoplasty, and cautery assisted uvulopalatoplasty. QT dispersion was calculated in each patient from pre-operative and post-operative surface ECG. Pre-operative and post-operative values were compared using the student's t test. P<0.05 was considered statistically significant.

RESULTS

One hundred and fourteen of the patients were male, 48 were female, and the mean age was 35.2+/-14.1 years (range: 21-51). No improvements were observed in 9 of the patients. Surgical interventions were successful in 153 patients (94%). Post-operative QTc max and QTc dispersion values were significantly shortened, and QTc min was increased compared to the pre-operative values (449.6+/-6.2 vs. 440.9+/-20.8, and 68.2+/-8.4 vs. 43.8+/-6.2, and 381.3+/-7.8 vs. 397.0+/-5.9 respectively; P=0.001).

CONCLUSION

This study shows that QT dispersion is increased in simple snoring patients without apnea and that QT dispersion decreases after surgical interventions.

Radiofrequency tissue volume reduction of the soft palate and UPPP in the treatment of snoring

The purpose of this study was to evaluate the efficiency of radiofrequency tissue volume reduction (RFTVR) and uvulopalatopharyngoplasty (UPPP) in the treatment of snoring in a prospective clinical trial of 79 patients consecutively undergoing surgery for snoring. Seventy-nine patients with primary snoring or mild OSAS (obstructive sleep apnea syndrome) were enrolled in this clinical trial (66 males and 13 females). According to the anatomical findings (the size of the tonsils and uvula), the patients underwent UPPP/TE of the RFTVR of the soft palate. Forty-seven patients had UPPP/TE (age 45.81+/-12.11 years; median AHI: 8; range 1-29). Thirty-two patients were treated with RFTVR of the soft palate (age 48.10+/-10.92; median AHI: 5.0; range 0-26). The average number of treatments was 2.2. All patients underwent preoperative polysomnography to exclude severe OSAS. Pre- and postoperative snoring scores were evaluated from the patients with bed partners. Postoperative follow-up data were collected at a median of 4 months after treatment; 85.1% of the UPPP group and 53.1% of the RFTVR group underwent postoperative polysomnography. Subjective snoring scores of all study participants were evaluated. Preoperatively, there was no statistically significant difference of subjective symptoms, age and BMI between the two groups. The snoring scores improved statistically significantly in both groups (P <0.001 in the UPPP group; P =0.001 in the RFTVR group). After UPPP/TE snoring improved in 37 patients (78.7%), and 29 (61.7%) thereof were free of bothersome snoring; no change was found in 9 patients (19.2%), and 1 (2.1%) worsened. In the RFTVR group, snoring improved in 15 (46.9%), and 9 (28.1%) thereof were free of bothersome snoring; no change was found in 13 patients (50%), and 1 worsened (3.1%). Preoperative AHI was statistically higher (P =0.016) and mean minimal oxygen saturation significantly lower (P =0.002) in the UPPP group. In the UPPP group AHI and HI showed statistically significant improvement postoperatively (P =0.025 and P =0.034, respectively). After RFTVR, no statistically significant change of AHI, HI or oxygen saturation was found. Besides limited mucosal erosions (15%) after RFTVR and foreign body sensations (<10%) after UPPP/TE, no side effects were observed. The success rate of RFTVR of the soft palate is lower compared to the more invasive technique of UPPP. Due to its minimally invasive character, RFTVR is suitable as first-step treatment for snoring, but patients should be counseled about possible success rates and different treatment options.

Snoring and the metabolic syndrome in women

OBJECTIVE

The main objective was to examine the association between metabolic syndrome, snoring and sleep quality among women.

METHODS

The study sample comprised healthy women (30-65 years) from the greater Stockholm area. Snoring and sleep quality were measured by the Karolinska Sleep Questionnaire. The metabolic syndrome was defined as the presence of two or more of the following components: (1) fasting serum glucose level > or =7.0 mmol/L; (2) arterial blood pressure > or =140/90 mmHg; (3) fasting serum triglycerides > or =1.7 mmol/L and/or HDL cholesterol <1.05 mmol/L; and (4) obesity (waist-to-hip ratio >0.85 and/or BMI > or =28 kg/m2).

RESULTS

After adjustment for age, the risk ratio of metabolic syndrome among snorers as compared to non-snorers was 4.50 (95% CI: 1.71-11.86; p=0.002). This association persisted after controlling for menopausal status, educational level, smoking, fatigue and exercise habits. Poor sleep quality showed a trend (OR: 3.31; 95% CI: 0.89-12.21; p=0.073) towards an increased risk for metabolic syndrome, but this did not reach statistical significance.

CONCLUSIONS

Snoring may be a strong predictor for metabolic syndrome in middle-aged women. These findings show that snoring women are not only at increased risk for individual risk factors associated with cardiovascular disease and type 2 diabetes, but also for metabolic syndrome.

Prevalence and correlates of habitual snoring in high school students

STUDY OBJECTIVES

To examine the prevalence and correlates of habitual snoring in senior high school students in Korea.

DESIGN

A cross-sectional survey.

SETTING

Ten high schools in the southern part of Seoul, Korea.

PARTICIPANTS

A total of 3,871 high school students (2,703 male students and 1,168 female students; age range, 15 to 18 years; mean age: male students, 16.8 years; female students, 16.9 years) who were attending the 11th grade.

MEASUREMENTS AND RESULTS

Data were collected on sociodemographic characteristics, school performance, and patterns of sleep and sleep-related disturbances. The overall prevalence of habitual snoring was 11.2% (boys, 12.4%; girls, 8.5%). The mean total sleep time was similar in habitual snorers vs nonsnorers (6.4 and 6.3 h per day, respectively). Frequency of snoring increased significantly with body mass index (BMI) [p < 0.001], cigarette smoking (p < 0.01), prevalence of witnessed apnea (p < 0.001), and Epworth sleepiness scale score (p < 0.001). The frequency of snoring increased with a decline in school performance (p < 0.001). For those whose school performance was low, there was a 35% excess in the odds of habitual snoring vs those whose school performance was high (odds ratio, 1.35; 95% confidence interval, 1.01 to 1.78).

CONCLUSIONS

These findings suggest that chronic habitual snoring is associated with multiple factors in adolescents. Whether interventions to modify BMI and smoking can alter snoring habits and related clinical problems warrants further study, particularly as it also may improve academic performance in high school students.

Poor sleep increases the prospective risk for recurrent events in middle-aged women with coronary disease. The Stockholm Female Coronary Risk Study

OBJECTIVE

We investigated the prognostic impact of sleep complaints in women with CHD and also examined whether the association between sleep problems and cardiac events could be explained by depression.

METHODS

All women patients, aged 65 or under who were admitted with an acute coronary syndrome between 1991 and 1994 in Stockholm, were followed for 5 years for recurrent coronary events. Sleep complaints and depression were measured at baseline using standardized questionnaires. Quality of sleep, restorative function of sleep, and snoring were assessed by the Karolinska Sleep Questionnaire (KSQ), and depressive symptoms by a questionnaire developed by Pearlin.

RESULTS

Poor sleep quality was associated with recurrent cardiac events. After multivariate adjustment for age, and standard risk factors, the hazard ratio (HR) for women with poor as compared with good sleep quality was 2.5 (95% CI: 1.2-5.2). Controlling for depression did not change this result substantial. Not waking up well-rested yielded a similarly increased risk (HR = 2.4; 95% CI: 1.2-4.6). Women with both poor sleep quality and depression had a worse prognosis than women free from these complaints (HR = 2.6; 95% CI: 1.0-6.4). Heavy snoring was not related to prognosis.

CONCLUSIONS

Our results indicate that poor sleep and sleep without a restorative function are associated with poor prognosis in female coronary patients. This association is not explained by depressive symptoms or by standard coronary risk factors.

Cardiovascular consequences of sleep-related breathing disorders

Sleep-related breathing disorders (SRBDs) represent a spectrum of abnormalities that range from simple snoring to upper airway resistance syndrome to sleep apnea. The clinical presentation may include obesity, snoring, neuropsychological dysfunction, and daytime hypersomnolence and tiredness. The acute hemodynamic alterations of obstructive sleep apnea include systemic and pulmonary hypertension, increased right and left ventricular afterload, and increased cardiac output. Earlier reports attributed the coexistence of SRBDs with cardiovascular diseases to the shared risk factors such as age, sex, and obesity. However, recent epidemiologic data confirm an independent association between SRBDs and the different manifestations of cardiovascular diseases. Possible mechanisms may include a combination of intermittent hypoxia and hypercapnia, repeated arousals, sustained increase in sympathetic tone, reduced baroreflex sensitivity, increased platelet aggregation, and elevated plasma fibrinogen and homocysteine levels. The strength of the association, its pathogenesis, and the impact of treatment of SRBDs on the health outcome of patients with cardiovascular diseases are issues to be addressed in future studies.

Prevalence of sleep apnoea and snoring in hypertensive men: a population based study

BACKGROUND

Several studies have reported an association between sleep disordered breathing (SDB) and hypertension (HT) but there is still a debate as to whether this is an effect of confounders. Some researchers have found an age dependent relationship between SDB and HT with higher risk at lower ages. A case-control study was performed in hypertensive men and non-hypertensive male controls matched for age and body mass index to assess whether there is an independent association between SDB and HT. If so, we further wanted to investigate whether this effect is age dependent.

METHODS

An overnight sleep study was performed in a population based, age stratified sample of 102 hypertensive men aged 43-82 years and 102 non-hypertensive controls.

RESULTS

Hypertensive subjects had a significantly higher prevalence of SDB than non-hypertensive subjects (apnoea-hypopnoea index (AHI): 10.8 v 7.3; desaturation index (DI): 8.5 v 5.2; AHI >or=10: 37% v 24%, p<0.05; DI >or=10: 29% v 12%; lowest desaturation: mean (SD) 81.9 (7.3) v 84.7 (6.1), p<0.01). After adjusting for neck circumference and physical inactivity, DI >or=10 and lowest desaturation were still independent predictors of HT with adjusted odds ratios of 2.3 (95% CI 1.0 to 5.3) and 0.94 (95% CI 0.89 to 0.99), respectively. When the subjects were split into two groups according to age (<60 and >or=60 years), the influence of DI >or=10 on HT was strongest in the younger men (adjusted OR 4.3 (95% CI 1.0 to 19.3 v 2.1 (95% CI 0.7 to 6.5)) and the association between minimum oxygen saturation (SaO(2)) and HT reached statistical significance in the younger men only.

CONCLUSION

SDB is more prevalent in men with HT than in controls. DI >or=10 and lowest desaturation are independent predictors of HT irrespective of confounders. The results indicate that the influence of SDB on HT is more pronounced in younger and middle aged men than in those above 60 years.

Familial Aggregation and Segregation Analysis of Snoring and Symptoms of Obstructive Sleep Apnea

To investigate possible modes of inheritance that would explain familial aggregation in obstructive sleep apnea (OSA), familial correlation and segregation analyses were performed on data derived from 584 pedigrees with 2019 cases enrolled in the Tucson Epidemiologic Study of Obstructive Airways Disease (TESOAD) who were at least 10 years of age and who had information pertaining to snoring and daytime sleepiness. Data were obtained from the 9th (May 1984 to October 1985) and 12th (February 1990 to October 1992) surveys of the TESOAD, which is a random, stratified sample of the non-Hispanic Caucasian population of Tucson, Arizona. A snoring phenotype was considered present if it occurred on at least some nights. A "sleep apnea" phenotype was constructed if participants snored and experienced daytime sleepiness. Familial correlations for snoring showed significant mother-child and sibling correlations but not father-child correlations. For sleep apnea, significant parent-daughter but not parent-son or sibling correlations were observed. Segregation analyses for snoring with regressive familial effects and sibling, age, and obesity covariates showed no evidence for mendelian transmission. However, additional familial effects were present that suggested phenotype aggregation from polygenic or environmental factors, or both. For the sleep apnea phenotype, similar segregation analyses indicated that mendelian dominant or codominant models were possible. However, the analyses also suggested that a nongenetic model fit the data as well. In addition, consistent with the familial correlations, specific maternal- and sibling-related effects remained even after inclusion of age, gender, and obesity covariates. These data support the concept that inheritable or shared environmental factors contribute to the development of OSA and that maternal components may be more important than paternal ones.

Role of snoring and daytime sleepiness in occupational accidents

To establish whether snoring and excessive daytime sleepiness (EDS), the main symptoms of obstructive sleep apnea syndrome, influence the risk of occupational accidents a population-based, prospective study was performed. In 1984, 2,874 men aged 30-64 answered questions on snoring and EDS. Ten years later 2,009 (73.8% of the survivors) responded to a follow-up questionnaire including work-related questions and potential confounders. Information on occupational accidents during 1985-1994 was obtained from national register data. A total of 345 occupational accidents were reported by 247 of the men (12.3%). Multivariate analysis revealed that men who reported both snoring and EDS at baseline were at an increased risk of occupational accidents during the following 10 yr, with an adjusted odds ratio of 2.2 (95% CI 1.3-3.8) after adjusting for age, body mass index, smoking, alcohol dependence, years at work, blue-collar job, shift work, and exposure to noise, organic solvents, exhaust fumes, and whole-body vibrations. However, no significant increased risk was found for snorers without EDS or nonsnorers with EDS. We conclude that sleepy, male snorers have an increased risk of occupational accidents. The results indicate that early identification and treatment of sleep-disordered breathing may reduce the number of injuries at work.

Obstructive sleep apnea and hypertension: from correlative to causative relationship

Sleep-disordered breathing, manifested by repetitive episodes of partial or complete cessation of breathing during sleep associated with brief arousal and autonomic activation, is estimated to affect as many as 4% of adult men and 2% of adult women. Studies conducted during the 1980s revealed a strong association between sleep-disordered breathing and hypertension. The results of these early studies, which relied on relatively small samples of patients, have been confirmed in recent years by large-scale epidemiologic studies that are controlled for all possible confounding factors. This paper reviews the evidence suggesting a causative relationship between hypertension and disordered breathing in sleep. The authors discuss the possible underlying mechanisms of the two entities and address the clinical implications of this relationship. They conclude by recommending a proactive approach to the diagnosis of breathing disorders in sleep, in order to prevent the cardiovascular sequelae of this syndrome.

CLINICAL REVIEW ARTICLE: Epidemiology of sleep-related obstructive breathing

The diagnosis of obstructive sleep apnoea syndrome (OSAS) and upper airway resistance syndrome (UARS) is based both on a combination of laboratory findings from whole-night sleep recordings and daytime symptoms. Due to the recent interest in breathing disturbances during sleep many prevalence studies have been performed within this field. There are, however, methodological difficulties in characterizing these syndromes in large populations; many of the studies have therefore been unable to present an overview of the complete syndromes but rather have focused on specific characteristics. In epidemiological research snoring and/or daytime sleepiness have often been used as markers of OSAS, while other studies have looked only on the respiratory disturbances or oxygen desaturation. Studies on the prevalence of OSAS based on polysomnography are reviewed here, as well as investigations where associated factors such as cardiovascular diseases and mortality were analysed. The interrelationships between snoring, daytime symptoms and laboratory findings are discussed. Gender, age, obesity, smoking, alcohol and ethnicity are all factors that influence the prevalence of OSAS. The data on associations between OSAS and cardiovascular disease or mortality are sometimes unrelated. Much of the discrepancy between different studies can be explained by the methodological difficulties connected with the definition of OSAS and also by the fact that the association between sleep-disordered breathing and cardiovascular outcome seems to be age-dependent.

Habitual snoring in an outpatient population in Japan

In order to investigate the occurrence and history of sleep problems in Japan, the 11-Centre Collaborative Study on Sleep Problems (COSP) project was carried out. Complaints of snoring are examined, and its prevalence, risk factors and screening reliability are discussed. The subjects who participated in the study were 6445 new outpatients from a general hospital. They were asked to answer a sleep questionnaire that consisted of 34 items with seven demographic items; each item was composed of four grades of frequency. In order to offset possible seasonal variations in sleep habits, data were collected across four seasons. Sleep patterns, insomnia, hypersomnia, parasomnia and circadian rhythm sleep disorders were covered. Habitual snoring was seen in 16.0% of males and 6.5% of females. Male predominance was noted. From these data, the relationship between habitual snoring and sleep complaints was statistically analyzed. Habitual snorers (HS) were observed to wake up more frequently during sleep (17.8% of males, 21.5% of females) than were non-habitual snorers (NHS; 6.6% of males, 9.7% of females). Mid-sleep awakening of HS was also more frequent than it was for NHS; however, there were no differences in difficulty in falling asleep and early morning awakening. Body mass index, cigarette smoking and alcohol consumption were also correlated with habitual snoring.

The role of habitual snoring and obesity in the development of diabetes: a 10-year follow-up study in a male population

OBJECTIVES

There are many similarities between diabetes (mainly type 2) and sleep breathing disturbances regarding risk factors, anthropometric criteria and consequences of morbidity and mortality. The aim of this study was to investigate whether the association between habitual snoring and diabetes is entirely dependent on obesity.

DESIGN

A population-based prospective study.

SETTING

The municipality of Uppsala, Sweden.

SUBJECTS AND METHODS

In 1984 and in 1994, 2668 men aged 30-69 years at baseline answered questionnaires concerning sleep breathing disturbances and somatic diseases.

RESULTS

Of those with habitual snoring in 1984, 5.4% reported that they had developed diabetes during the 10-year period compared with 2.4% of those without habitual snoring (P < 0.001). Amongst obese snorers, 13.5% developed diabetes compared with 8.6% of obese non-snorers (P = 0.17). In a multiple logistic regression model, the odds ratio (95% confidence interval) for development of diabetes was higher in obese snorers [7.0 (2.9-16.9)] than in obese non-snorers [5.1 (2.7-9.5)] after adjustment for age, weight gain, smoking, alcohol dependence and physical inactivity.

CONCLUSIONS

We conclude that, in males aged 30-69 years, habitual snoring is associated with an increased incidence of diabetes within 10 years. Although obesity is the main risk factor for developing diabetes, coexistent habitual snoring may add to this hazard.

Compliance with CPAP in elderly patients with OSA

Background: Obstructive sleep apnea (OSA) is common in the general population and especially in the geriatric age group. Nasal continuous positive airway pressure (CPAP) is a highly effective treatment but can be difficult for some patients to use.Objective: We investigated the question if older patients were less compliant with CPAP therapy than younger patients and may not realize its benefits.Methods: We conducted a prospective, non-randomized study comparing use of CPAP in patients over age 65 with patients under age 65. One hundred and seven consecutive patients with a new diagnosis of obstructive sleep apnea were started on therapy with nasal CPAP. We obtained follow-up data on all 107 patients. Compliance with CPAP was assessed by patients subjective report of use and, in a subset of 21 patients, by objective measurement using a microchip installed in the CPAP unit that measures actual hours of use at therapeutic pressure.Results: The percentage of patients using CPAP regularly was not different in the two groups: 70% of patients in the over age 65 group used CPAP regularly vs. 72% of patients under age 65. The over 65 group used CPAP 6.5 nights per week, an average of 6.5 h of use per night. The under 65 group was not significantly different, using CPAP 6.8 nights per week, a mean of 6.7 h of use per night.Conclusion: Patients over age 65 are able to tolerate CPAP as well as patients under age 65.

Prospective study of the association between sleep-disordered breathing and hypertension

BACKGROUND

Sleep-disordered breathing is prevalent in the general population and has been linked to chronically elevated blood pressure in cross-sectional epidemiologic studies. We performed a prospective, population-based study of the association between objectively measured sleep-disordered breathing and hypertension (defined as a laboratory-measured blood pressure of at least 140/90 mm Hg or the use of antihypertensive medications).

METHODS

We analyzed data on sleep-disordered breathing, blood pressure, habitus, and health history at base line and after four years of follow-up in 709 participants of the Wisconsin Sleep Cohort Study (and after eight years of follow-up in the case of 184 of these participants). Participants were assessed overnight by 18-channel polysomnography for sleep-disordered breathing, as defined by the apnea-hypopnea index (the number of episodes of apnea and hypopnea per hour of sleep). The odds ratios for the presence of hypertension at the four-year follow-up study according to the apnea-hypopnea index at base line were estimated after adjustment for base-line hypertension status, body-mass index, neck and waist circumference, age, sex, and weekly use of alcohol and cigarettes.

RESULTS

Relative to the reference category of an apnea-hypopnea index of 0 events per hour at base line, the odds ratios for the presence of hypertension at follow-up were 1.42 (95 percent confidence interval, 1.13 to 1.78) with an apnea-hypopnea index of 0.1 to 4.9 events per hour at base line as compared with none, 2.03 (95 percent confidence interval, 1.29 to 3.17) with an apnea-hypopnea index of 5.0 to 14.9 events per hour, and 2.89 (95 percent confidence interval, 1.46 to 5.64) with an apnea-hypopnea index of 15.0 or more events per hour.

CONCLUSIONS

We found a dose-response association between sleep-disordered breathing at base line and the presence of hypertension four years later that was independent of known confounding factors. The findings suggest that sleep-disordered breathing is likely to be a risk factor for hypertension and consequent cardiovascular morbidity in the general population.

Snoring and risk of cardiovascular disease in women

OBJECTIVES

To examine prospectively the association between snoring and incidence of cardiovascular disease (CVD) in women.

BACKGROUND

Whether snoring increases risk of CVD remains unclear; most previous studies have been small, not prospective and limited to men.

METHODS

Seventy-one thousand seven hundred seventy-nine female nurses 40 through 65 years of age and without previously diagnosed CVD or cancer at baseline in 1986 were followed up for eight years. Frequency of snoring was assessed using mailed questionnaires at baseline.

RESULTS

During eight years of follow-up, we documented 1,042 incident cases of major CVD events (644 coronary heart disease [CHD] and 398 stroke). Compared with nonsnorers, the age-adjusted relative risks (RRs) of CVD were 1.46 (95% confidence interval 1.23 to 1.74) for occasional snorers and 2.02 (1.62 to 2.53) for regular snorers. The age-adjusted RRs of CHD were 1.43 (1.15 to 1.77) for occasional snorers and 2.18 (1.65 to 2.87) for regular snorers. The age-adjusted RRs of stroke were 1.60 (1.21 to 2.12) and 1.88 (1.29 to 2.74), respectively. After further adjustment for smoking, body mass index (BMI) and other covariates, the positive association between snoring and CVD was attenuated but remained statistically significant (RRs of CVD were 1.20 [1.01 to 1.43] for occasional snorers and 1.33 [1.06-1.67] for regular snorers.

CONCLUSIONS

These data suggested that snoring is associated with a modest but significantly increased risk of CVD in women, independent of age, smoking, BMI and other cardiovascular risk factors. While further study is needed to elucidate the biological mechanism underlying this association, snoring may help clinicians identify individuals at higher risk for CVD.

Correlates of the "don't know" response to questions about snoring

Many persons say that they "don't know" whether they snore. The purpose of this study was to investigate the prevalence and correlates of such responses in an elderly population. Subjects were 1715 members (1,155 men, 560 women) of a previously defined cohort (Western Group Collaborative Study) followed prospectively since 1960-1961 with a current mean age of 75.9 (SD = 4.3) for the men and 71.4 (SD = 5.3) for the women. We collected survey questionnaires and reviewed medical records. Results indicated that risk factors for the "don't know" response in this population were similar to those for frequent snoring and included: male sex, higher Body Mass Index, smoking, and use of sinus medication. Between 28 and 44% of the cohort answered questions about snoring with a "don't know" response. These data are compatible with the interpretation that subjects may disavow knowledge of their own snoring and suggest that future studies consider the "don't know" response to questions about snoring as a response of potential interest.

Recognition and consequences of obstructive sleep apnea hypopnea syndrome

There is a growing recognition of sleep-disordered breathing (SDB) in patient groups and in the general population. This article reviews issues related to recognizing the disorder, including the problems of relying on narrowly defined polysomnographic data for case findings and for assessment of disease severity. The distributions of symptoms and physiologic measurements of SDB in the population and their inter-relationships are reviewed. The epidemiological data that address risk factors and consequences of sleep apnea hypopnea syndrome (SAHS) also are discussed, with recommendations regarding recognition priorities.

Increased mortality among sleepy snorers: a prospective population based study

BACKGROUND

The long term health consequences of snoring and sleep apnoea syndrome are still uncertain. This study was conducted to assess the mortality risk associated with snoring and excessive daytime sleepiness (EDS), the two main symptoms of sleep apnoea syndrome, in men.

METHODS

In 1984 a sample of 3100 men aged 30-69 responded to a postal questionnaire including questions about snoring, EDS, and the prevalence of various diseases (response rate 77.1%). Mortality data for the period 1985-1995 were collected for the complete sample.

RESULTS

During the 10 year follow up period 213 men died, 88 of cardiovascular diseases. Compared with subjects with no snoring or EDS in 1984, men with isolated snoring or EDS displayed no significantly increased mortality. The combination of snoring and EDS was associated with a significant increase in mortality. However, the relative rates decreased with increasing age, and in men aged 60 and above no effect on mortality was found. Men below the age of 60 with both snoring and EDS had an age adjusted total death rate which was 2.7 times higher than men with no snoring or EDS (95% CI 1.6 to 4.5). The corresponding age adjusted hazard ratio for cardiovascular mortality was 2.9 (95% CI 1.3 to 6.7) for subjects with both snoring and EDS. Further adjustment for body mass index and reported hypertension, cardiac disease, and diabetes reduced the relative mortality risk associated with the combination of snoring and EDS to 2.2 (95% CI 1.3 to 3.8) and the relative risk of cardiovascular mortality to 2.0 (95% CI 0.8 to 4.7).

CONCLUSION

Snoring without EDS does not appear to carry an increased risk of mortality. The combination of snoring and EDS appears to be associated with an increased mortality rate, but the effects seems to be age dependent. The increased mortality is partly explained by an association between "snoring and EDS" and cardiovascular disease.

Recognition and consequences of obstructive sleep apnea hypopnea syndrome

There is a growing recognition of sleep-disordered breathing (SDB) in patient groups and in the general population. This article reviews issues related to recognizing the disorder, including the problems of relying on narrowly defined polysomnographic data for case findings and for assessment of disease severity. The distributions of symptoms and physiologic measurements of SDB in the population and their inter-relationships are reviewed. The epidemiological data that address risk factors and consequences of sleep apnea hypopnea syndrome (SAHS) also are discussed, with recommendations regarding recognition priorities.

Gender and the systemic hypertension-snoring association: a questionnaire-based case-control study

Since the role of gender in the association between hypertension and snoring is unknown, we studied it while accounting for age and body mass index (BMI) as confounding variables. A questionnaire on snoring was administered to 90 hypertensive (HT) subjects (45 men and 45 women) and to 90 normotensive (NT) subjects matched for gender, age and BMI. As expected, snoring was more commonly reported by men than by women, but no significant difference was found between HT and NT men, irrespective of age. Conversely, heavy snoring was more frequently reported by HT than NT women; habitual snoring was more common among young (age < 50 years) HT than NT women; and heavy snoring was more common among older (age > 50 years) HT than NT women. These data suggest an effect of gender on the hypertension-snoring association: in men, snoring may be accounted for by age and BMI whether or not hypertension is present, whereas in women the natural history of snoring appears different and more severe in HT than in NT. Although the mechanism(s) responsible for the differences between men and women are obscure at present, gender may be an important variable in the systemic hypertension-snoring association.

Sleep-disordered breathing in healthy, aged persons. Fifth and final year follow-up

The frequency of sleep-disordered breathing (SDB) events increases dramatically with age, although the clinical significance of this phenomenon is uncertain. We report herein on data from the fifth follow-up observation of a cohort of healthy elderly which we selected, evaluated, and followed up in an effort to address this issue. Baseline observations on this group of 95 normal older persons medically screened for good health included standard nocturnal polysomnograms and daytime assessment of medical, sleep/wake, and psychological variables. At fifth-year follow-up, 42 subjects returned for assessment. Comparison of returning vs nonreturning subjects indicated no significant differences in baseline characteristics between these groups. Division of returning subjects into moderate (apnea-hypopnea index [AHI] > or = 5) vs low (AHI < 5) SDB at baseline resulted in 10 subjects in the moderate group and 32 subjects in the low group. The two groups were comparable with regard to sex, weight, and education, although the moderate SDB group was significantly older (70.4 years) than the low SDB group (64.8 years). Follow-up medical, sleep/wake, and psychological data were contrasted for the two groups using a mixed design multivariate analysis of variance (repeated measures factor-time-6 observations; between-subjects factor SDB level, 2 groups). There were no statistically significant effects of SDB or interactions of SDB and time across this 5-year follow-up. These results confirm observations from the third-year follow-up. We conclude that observation of a moderate level of SDB in an otherwise healthy older person is apparently not a significant risk across a 5-year follow-up period and therefore does not seem to warrant investigation beyond a thorough medical history and physical examination to rule out other disorders.

Snoring and atherosclerotic manifestations in a 70-year-old population

A number of studies have demonstrated an association between habitual snoring and ischemic heart disease like angina pectoris, myocardial infarction and ischemic changes on the electrocardiography (ECG). Control for the influence of potential confounders has been inadequate. To further elucidate the issue we examined the association between self-assessed snoring and the relation to atherosclerotic manifestations. 804 70-year-old males and females were classified according to snoring habits. Alcohol and tobacco consumption, blood pressure, body mass index, social group, plasma lipids (triglycerides, cholesterol, high density lipoprotein), fasting blood glucose, glucose tolerance test, plasma epinephrine and norepinephrine were determined. Presence of angina pectoris, claudication intermittens, use of nitroglycerine were questioned, a resting ECG and a distal arterial pressure by use of doppler technique in the lower limbs were determined. Distal atherosclerotic manifestations was defined as complaints of claudication intermittens, pulselessness in one or more foot arteries or a foot/arm systolic pressure ratio < 0.90. ECG changes were classified in accordance to standard criteria (Minnesota codes) into positive ECG signs (Q/OS waves, S-T depressions, T-wave inversion or flattering or left bundle branch block) and definitive myocardial infarction. Snoring showed a weak positive correlation to positive ECG signs and definitive myocardial infarction, but after adjustments for the above confounders, no association was found between snoring and atherosclerotic manifestations. We conclude that, in a 70-year-old population, self-reported snoring is not associated with atherosclerotic manifestations.

Habitual snoring as a risk factor for brain infarction

The association of habitual snoring with cerebral ischaemia was studied, in a case control-study, in 133 patients aged 45-75 years (103 men and 30 women) and 133 controls matched for sex and age. Ischaemic stroke was confirmed by brain computed tomography or magnetic resonance imaging. History of risk factors, especially of snoring and sleeping habits was recorded with structured questionnaire during interview. Prevalence of habitual snoring significantly differs between patients with stroke and controls: 31/133 (23.3%) vs 11/133 (8.3%) (Odds ratio 3.4, 95% confidence interval 1.5 to 7.6, p < 0.001). Even after adjusting for matching variables and confounding risk factors (arterial hypertension, cardiac arrhythmia, and obesity), habitual snoring carries a significant risk factor for stroke (odds ratio: 2.9, 95% confidence interval 1.3 to 6.8 (p = 0.01)). The risk of ischaemic stroke was higher among older male patients with arterial hypertension who always snored. Habitual snoring was not significantly linked with sleep-related stroke nor with the pathophysiology of strokes. Inquiring about habitual snoring should become a routine practice, especially among older male patients with arterial hypertension, and specific preventive measures should be instituted at an earlier stage.

Epidemiological aspects of snoring and hypertension

Previous studies have reported a great difference in snoring prevalence in different populations. In a recent study on men and women 20-45 y old, living in Sweden (Uppsala, Gothenbourg), Iceland (Reykjavík) and Belgium (Antwerp), data concerning snoring, etc., were collected using the same questions and scales in all the countries. In all four areas the prevalence of snoring was the same: 5% of men and 2-3% of women reported snoring every night. In all areas snoring was positively correlated with age, male sex and body mass index. It was therefore assumed that the previous difference in snoring prevalence is probably an artifact of different methodologies. The connection between snoring and systemic hypertension has been much disputed during the last decade. The high prevalence of hypertension in the sleep apnoea syndrome has been explained by obesity/age/male gender/sleep apnoea and/or snoring. In one recent study snoring did not contribute independently to the prediction of hypertension, while other studies indicate that snoring is an independent risk factor for hypertension. After reviewing some of the epidemiological literature it was found that these studies are bound to identify almost entirely different subgroups of the population as snorers since the prevalence of snoring is rated on different types of frequency scales with words like 'never', 'often' or the number of nights per week. The questions used are also different. In general it can be stated that the smaller the proportion of the population identified as snorers the more often there is a statistically significant association with hypertension. The relationship between snoring and hypertension is considered to be unclear due to the different research methods used, and to the uncertain role played by confounding factors such as obesity. There is a need for population-based, prospective, studies with more uniform definitions of the term 'snoring' based on objective measurements of upper airway resistance during sleep, together with haemodynamic studies.

Haemodynamics during sleep: old results and new perspectives

After the advent of polygraphic recordings in the 1960s a great deal of interest focused on cardiocirculatory and respiratory activity during sleep. The Bologna sleep laboratory was the first to make direct recordings of systemic arterial pressure, pulmonary arterial pressure and alveolar ventilation in normal subjects, measuring gas-blood values during different sleep stages. In the 1960s, neurophysiologists rediscovered a syndrome known to pneumologists for a decade as Pickwickian Syndrome. Polygraphic studies performed in sleep laboratoires all over Europe (Germany, France and Italy) led to a major discovery: the syndrome was not caused by respiratory overload due to obesity, but usually by the presence of obstructive apnoeas arising during sleep. By means of continuous sleep recordings, our laboratory documented the severe repercussions of apnoeas on ventilatory and cardiocirculatory functions. Hypnologists pointed to tracheostomy as the logical effective treatment for the syndrome. Surgery was first performed in Germany by Kuhlo and coworkers and then in Bologna. In the early 1970s, following the Bologna group's research, there emerged the now accepted concept that obstruction of the upper airways is a continuum stretching from snoring to full-blown sleep apnoea syndrome. The Bologna team was also the first to conduct epidemiological surveys that indicated that snoring is a relevant risk factor for the cardiocirculatory system. Here the trends of haemodynamic and ventilatory parameters during sleep are investigated in syndromes of obstructive respiratory failure. The conclusion is that sleep, particularly REM-sleep, exacerbates all these disorders, and the topic provides a basis for a wider look at how cardiocirculatory activity varies during sleep under normal and pathological conditions.

Basic Nordic Sleep Questionnaire (BNSQ): a quantitated measure of subjective sleep complaints

Sleep-related breathing disturbances, especially obstructive sleep apnoea syndrome (OSAS), are commonly encountered. Epidemiological studies from different countries have shown that poor sleep and complaints about insufficient sleep or poor sleep are often related to poor health. Different studies are, however, difficult to compare with each other. One of the main reasons for this is the frequent methodological differences between questionnaires. There is a need for uniform methods: we need to know the prevalence and incidence of sleep disorders, judged using the same criteria, and also the severity of each problem, i.e. how often a problem or a symptom happens/occurs. In 1988 the Scandinavian Sleep Research Society formed a task group for developing a standardized questionnaire that could be used as a basis for questionnaires used in the Nordic countries. In this article we describe the Basic Nordic Sleep Questionnaire (BNSQ). The main change compared to many previous questionnaires is the five-point scale (scale from 1 to 5) stressing on how many nights/days per week something happens. The basic scale is: 1, 'never or less than once per month'; 2, 'less than once per week'; 3, 'on 1-2 nights per week'; 4, 'on 3-5 nights per week'; and 5, 'every night or almost every night'. For questions about specific rare events the first category may be divided into 'never' and 'less than once per month'. Habitually occurring events such as 'habitual snoring' are defined here as snoring every night or almost every night. The BNSQ has been used widely in a variety of studies performed in Nordic countries during the last years, and it has proven to be a valid tool.

Daytime sleepiness, snoring and gastro-oesophageal reflux amongst young adults in three European countries

OBJECTIVES

To study the geographical variation in daytime sleepiness, snoring and disrupted breathing during sleep and to identify and compare risk factors using the same method in four European cities.

DESIGN

A cross-sectional, multicentre epidemiological survey.

SETTING

Reykjavik in Iceland, Uppsala and Göteborg in Sweden and Antwerp in Belgium.

PARTICIPANTS

A random population sample of 2202 subjects who participated in the European Community Respiratory Health Survey.

MAIN OUTCOME MEASURES

Sleep disturbances and daytime symptoms.

RESULTS

At all the centres, 5% of the men and 2-3% of the women reported snoring every night. Daytime sleepiness (DS) was more often reported in Uppsala [odds ratio (OR) and 95% confidence interval: 1.6 (1.2-2.1)] than in the other centres, whilst daytime tiredness (DT) was most common in Reykjavik [ OR 1.8 (1.4-2.1)]. Snoring was positively correlated with age, male gender and body-mass index in all areas. Symptoms of gastro-oesophageal reflux were associated with DS: OR 2.6 (1.5 4.4) and DT: OR 4.5 (2.7-7.6) and disrupted breathing: OR 3.8 (1.4-10). DS and DT were reported more often by women than by men.

CONCLUSION

The prevalence of snoring was about the same in all four areas, whilst there was a geographical variation in daytime sleepiness and tiredness. As complaints of DS and DT and disrupted breathing were more common in subjects who reported symptoms of gastro-oesophageal reflux, we suggest that polysomnographic studies comparing sleep patterns in adult patients with and without reflux should be conducted.

Snoring may be linked to culture

The estimates of the incidence of snoring in adults that have been provided by four epidemiological studies vary from 16-89% of the population. Collectively, these data are completely confounded by country of origin and thus may reflect cultural differences that contribute to snoring. While the etiology of snoring is not fully known, speculation has focused on gender and age as primary factors that contribute to this behavior. Within the limitations imposed by the designs of these four studies, we compared the relative strength of the relationships between snoring and gender, age, and culture. These analyses suggest that certain variables associated with cultures appear to be more salient than both gender and age, as determinants of snoring.