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Keywords:

  • carotid atherosclerosis;
  • epidemiology;
  • snoring

Summary

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflicts of interest
  9. References
  10. Supporting Information

Previous studies have suggested that self-reported snoring is associated with atherosclerotic vascular diseases. However, the role of self-reported snoring as an independent risk factor for subclinical atherosclerosis has not been well established. This study aimed to evaluate whether and to what extent self-reported snoring is associated with subclinical carotid atherosclerosis after adjusting for traditional cardiovascular risk factors. Carotid intima-media thickness and plaque were investigated with ultrasonography in 1245 urban Chinese aged 50–79 years between September 2007 and November 2007. Information on self-reported snoring and measurements of traditional cardiovascular risk factors was also collected. A total of 1050 participants were involved in the final analysis. The prevalence of self-reported snoring habitually (snoring frequency ≥5 days per week) was 31.5, and 64.3% of the participants in this population had a history of snoring. The mean values of the maximum intima-media thickness of bifurcation and common carotid arteries in snorers were significantly higher than in non-snorers (1.08 ± 0.14 mm versus 1.04 ± 0.14 mm, < 0.001, in carotid bifurcation; 1.03 ± 0.15 mm versus 1.00 ± 0.15 mm, = 0.002, in common carotid artery). After adjustment for traditional cardiovascular risk factors, logistic regression analysis showed that the odds ratio of self-reported snoring habitually for increased intima-media thickness and carotid bifurcation plaque was 1.71 [95% confidence interval (CI): 1.22–2.39; = 0.002] and 3.63 (95% CI: 2.57–5.12; < 0.001), respectively. In conclusion, the current study suggested that self-reported snoring is associated significantly with carotid bifurcation intima-media thickness and the presence of plaque, independent of traditional cardiovascular risk factors.


Introduction

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflicts of interest
  9. References
  10. Supporting Information

Atherosclerosis is a chronic, progressive, pathological process with a long asymptomatic subclinical phase. Disease progression can lead to the occurrence of cardiovascular events such as coronary heart disease and stroke. The increased intima-media thickness (IMT) and plaque of the carotid artery, as measured by B-mode ultrasound imaging, have been well established as reliable and valid non-invasive markers for subclinical atherosclerosis. The traditional cardiovascular risk factors, such as age, smoking, elevated serum cholesterol, hypertension and diabetes, can explain the presence of carotid atherosclerosis to a certain extent, but the complex aetiology of carotid atherosclerosis has not yet been elucidated fully. It is therefore necessary to search for additional risk factors of subclinical carotid atherosclerosis, which is the pathological basis of subsequent cardiovascular events, including stroke. Snoring is a common consequence of an increase in upper airway resistance during sleep, which is characterized by loud upper airway breathing sounds during sleep produced by vibration of the pharyngeal wall and its associated structures (Liistro et al., 1991). Increasing evidence from epidemiological studies has indicated that self-reported snoring was associated significantly with atherosclerotic cardiovascular diseases, including stroke (D’Alessandro et al., 1990; Hu et al., 2000; Koskenvuo et al., 1987; Neau et al., 1995; Palomäki, 1991), but the role of self-reported snoring as a risk factor for subclinical carotid atherosclerosis has not been well established.

Snoring occurs commonly in the general population, with up to 47.7% of men and 33.6% of women reporting habitual snoring (Ohayon et al., 1997; Young et al., 1993). A recent study showed that heavy snoring (snoring sleep time more than 50%) may be a risk factor for carotid atherosclerosis (Lee et al., 2008). However, despite such reports, most clinical interest has focused primarily on the link between obstructive sleep apnoea (OSA) and premature atherosclerosis (Baguet et al., 2009; Drager et al., 2005). In contrast to OSA, self-reported snoring is recognized more easily by people and clinical doctors. Additionally, self-reported snoring is used widely in epidemiological studies (Fitzpatrick et al., 1993; Hiestand et al., 2006; Hu et al., 2000; Koskenvuo et al., 1987; Palomäki, 1991), and obtaining information from the general population is more convenient. Moreover, self-reported snoring represents an integrated statement over time and can reflect snoring frequency, which cannot be achieved by one whole-night measurement. Hence, this may assist with recognition of individuals having a potential risk for developing atherosclerosis in the general population through an epidemiological survey on the relationship between self-reported snoring and carotid atherosclerosis; furthermore, this will aid in the early prevention of atherosclerotic cardiovascular and cerebrovascular diseases.

The aim of this study is to evaluate whether and to what extent self-reported snoring is associated with carotid artery IMT and carotid plaque after adjusting for traditional cardiovascular risk factors in a general population from urban China.

Methods

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflicts of interest
  9. References
  10. Supporting Information

Participants

Participants in the present study were community residents (from Beijing, China) who were selected using a stratified random sampling method as part of the Chinese Multi-Provincial Cohort Study (Liu et al., 2004; Zhao et al., 2007). A carotid ultrasound examination was conducted on 1245 urban Chinese aged 50–79 years between September 2007 and November 2007. Information on self-reported snoring and measurements of traditional risk factors was also collected. Subjects with previously diagnosed stroke, coronary heart disease or transient ischaemic attack were excluded. A total of 1050 subjects were involved in the final analysis, dependent on complete data information on self-reported snoring and measurements of cardiovascular risk factors as well as results from ultrasound scan of the carotid artery.

Written informed consent was obtained from all participants, and the study was approved by the Ethics Committees of Capital Medical University Affiliated Beijing Anzhen Hospital and Beijing Institute of Heart, Lung and Blood Vessel Diseases.

Data collection

Snoring status was assessed according to self-reported snoring habits. Information on self-reported snoring was obtained using a standardized questionnaire in which we asked the following: (i) do you snore (yes or no); and (ii) how often do you snore? (1 = 1 day per week, 2 = 2–4 days per week, 3 = ≥5 days per week). Those who reported snoring more than 5 days per week were regarded as self-reported habitual snorers. In addition, demographic information, smoking status, alcohol intake and detailed medical history were also collected using the same standardized questionnaire. Regular smoking of more than one cigarette per day was defined as currently smoking. Alcohol intake was defined by drinking amount on a weekly basis.

Anthropometric measurements included height, weight, waist circumference and hip circumference. Body mass index (BMI) as a relative weight index was calculated as weight in kilograms divided by height squared in metres. Blood pressure measurements were determined by a mean of three consecutive readings of systolic and diastolic blood pressure obtained with a mercury sphygmomanometer. Hypertension was defined by a mean systolic blood pressure ≥140 mmHg and/or a mean diastolic blood pressure ≥90 mmHg and/or current antihypertensive therapy.

Venous blood samples were drawn from the antecubital vein in the morning after 12-hour fasting and following blood pressure measurement. Serum glucose, total cholesterol (TC) and triglycerides (TG) were determined by standard enzymatic methods, and high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) were measured by a homogeneous assay. High sensitivity C-reactive protein (hsCRP) was measured by immunoturbidimetry. Diabetes was defined by fasting glucose ≥7.00 mmol L−1 and/or current hypoglycaemic therapy. Dyslipidaemia was defined by TC ≥5.18 mmol L−1 and/or TG ≥1.70 mmol L−1 and/or HDL-C < 1.04 mmol L−1 and/or LDL-C ≥ 3.37 mmol L−1 and/or receiving specific drug treatment.

Carotid ultrasonography

The carotid ultrasound examination was performed using an Aloka Prosound α10 (Aloka Medical, Tokyo, Japan) with a 7.5 MHz linear array transducer. Trained sonographers performed ultrasound scans on participants in a supine position with the head slightly extended and turned in the opposite direction to the carotid artery being studied. The images were recorded at 12 different carotid sites (i.e. right and left, near and far walls, common, bifurcation and internal carotid artery), according to a standardized protocol. There were two parallel hyperechogenic lines (blood-intima and media-adventitia interfaces) separated by a hypoechogenic space on the longitudinal scan of the B mode image of the carotid artery. The distance between the two lines was defined as the IMT (Pignoli et al., 1986). The maximal value of IMT at the 12 sites was selected and the final IMT of each carotid segment (i.e. common, bifurcation and internal carotid artery) was considered the mean of maximum IMT values at the four sites (i.e. right and left, near and far walls). The mean of the maximum IMT of the carotid bifurcations and the common carotid arteries was used to designate increased IMT in the present analysis, and an increased IMT was defined as IMT ≥1 mm (Simon et al., 2002). Plaque was defined as IMT ≥1.3 mm (Mancia et al., 2001) or an echogenic structure encroaching into the vessel lumen with a distinct area, having an IMT >50% greater than that of the neighbouring sites (Baguet et al., 2005), based on the single thickest wall in each arterial segment.

The carotid ultrasound examination was conducted by seven sonographers. All ultrasound scans were sent to the ultrasound reading centre and analysed manually by a single reader who underwent initial training and certification, with analyses performed using a GE EchoPAC digital reading station. To assess the reproducibility of IMT measurements, we re-examined 15 participants (1.2% random samples) 1 week after the initial visit. The intrasonographer coefficient of variation of IMT measurements was 4.0%, and the intersonographer coefficient of variation of IMT measurements was 7.8%. To assess the reproducibility of IMT image analysis, 20 image sequences were selected to be analysed twice by the same reader and also analysed once by another same-level reader. The within-reader coefficient of variation was 4.1% and the between-reader coefficient of variation was 5.6%.

Statistical analysis

Group data were presented as mean ± standard deviation (SD) for normal distributions and n (%) or median (interquartile range) for skewed distributions. Group comparisons were performed using Student’s t-test or an analysis of variance or chi-square test as appropriate. The Bonferroni correction was used for multiple comparisons. Multivariable logistic regressions were used to analyse the relationship of self-reported snoring variables with carotid increased IMT and carotid plaque. Odds ratios (OR) with 95% confidence intervals (CI) were calculated to quantify the degree of association. Nagelkerke R-squares were computed to measure the variation of increased IMT and plaque of the carotid artery attributed to risk factors including or not including self-reported snoring variable. Possible confounding factors adjusted by multivariable logistic regression model were age, sex, smoking, alcohol intake, BMI, TG, HDL-C, LDL-C, hypertension, diabetes and hsCRP. All data analyses were performed with spss version 13.0 statistical software (SPSS, Chicago, IL, USA). A two-sided P-value <0.05 was considered statistically significant.

Results

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflicts of interest
  9. References
  10. Supporting Information

The distribution of study participants’ characteristics are presented in Table 1, both overall and by whether self-reported snoring. Compared with non-snorers, snorers included a larger proportion of men, were more likely to be overweight or obese (62.8 versus 45.9%, < 0.001) and had a higher prevalence of hypertension. Waist circumference, body mass index, systolic blood pressure and triglycerides were significantly higher and high-density lipoprotein cholesterol was significantly lower in snorers. In addition, the prevalence of patients taking antihypertensive medication was higher among snorers than non-snorers (Table 1).

Table 1.   Characteristics of the study population
CharacteristicsOverall (= 1050)Self-reported snoringP-value*
No (= 375)Yes (= 675)
  1. *For comparisons between non-snorers and snorers. †Dyslipidaemia was classified as hypercholesterolaemia, hypertriglyceridaemia, low levels of high-density lipoprotein cholesterol, high-levels of low-density lipoprotein cholesterol, or was considered as receiving drug treatment. BMI, body mass index; SD, standard deviation.

Age, mean ± SD, years65.3 ± 7.964.8 ± 8.165.5 ± 7.90.12
Men, n (%)476 (45.3)136 (36.3)340 (50.4)<0.001
Smoking, n (%)
 Total156 (14.9)46 (12.3)110 (16.3)0.08
 Male154 (32.4)46 (33.8)108 (31.8)0.10
 Female2 (0.3)0 (0)2 (0.6)0.54
Alcohol intake, n (%)166 (15.8)56 (14.9)110 (16.3)0.56
BMI, mean ± SD, kg m−224.66 ± 3.1623.99 ± 3.1425.03 ± 3.11<0.001
Waist circumference, mean ± SD, m0.85 ± 0.090.83 ± 0.090.87 ± 0.09<0.001
Overweight and obesity, n (%)
 BMI ≥ 24 kg m−2 & <28 kg m−2452 (43.0)132 (35.2)320 (47.4)<0.001
 BMI ≥ 28 kg m−2144 (13.7)40 (10.7)104 (15.4)<0.001
Systolic blood pressure, mean ± SD, mmHg137.1 ± 17.1135.4 ± 17.5138.0 ± 16.90.02
Diastolic blood pressure, mean ± SD, mmHg82.5 ± 9.682.0 ± 9.582.7 ± 9.60.22
Total cholesterol, mean ± SD, mmol L−15.34 ± 1.015.30 ± 0.965.36 ± 1.040.37
Triglycerides, mean ± SD, mmol L−11.80 ± 1.191.66 ± 0.841.88 ± 1.330.001
High-density lipoprotein cholesterol, mean ± SD, mmol L−11.33 ± 0.261.35 ± 0.271.31 ± 0.250.02
Low-density lipoprotein cholesterol, mean ± SD, mmol L−13.30 ± 0.893.27 ± 0.863.31 ± 0.900.44
Fasting glucose, mean ± SD, mmol L−15.90 ± 1.025.85 ± 1.115.92 ± 0.960.29
Hypertension, n (%)654 (62.3)205 (54.7)449 (66.5)<0.001
Diabetes, n (%)218 (20.8)81 (21.6)137 (20.3)0.67
Dyslipidaemia,n (%)809 (77.0)287 (76.5)522 (77.3)0.77
Treatment, n (%)
 Antihypertensive agents466 (71.2)130 (63.4)336 (74.8)<0.001
 Antidiabetic agents114 (52.3)42 (51.8)72 (52.5)0.79
 Statins147 (18.2)44 (15.3)103 (19.7)0.11
High sensitivity C-reactive protein, median (interquartile range), mg L−10.97 (0.44–2.16)0.90 (0.44–2.01)1.00 (0.46–2.22)0.36

The prevalence of self-reported snoring habitually (snoring frequency ≥5 days per week) was 31.5, and 64.3% of participants in this study population had history of snoring. While we stratified snorers into subgroups according to snoring frequency, the prevalence of self-reported snoring more than 5 days per week was higher in men than in women (35.1 versus 28.6%, = 0.02). Moreover, 49.0% of snorers reported snoring more than 5 days per week (Table 2).

Table 2.   Distributions of self-reported snoring by frequency in the study population
Snoring frequencyOverall % (no./n)Men % (no./n)Women % (no./n)P-value*
  1. *For comparisons of snoring distributions between men and women.

Prevalence
 1 day per week10.1 (106/1050)8.6 (41/476)11.3 (65/574)0.15
 2–4 days per week22.7 (238/1050)27.7 (132/476)18.5 (106/574)<0.001
 ≥5 days per week31.5 (331/1050)35.1 (167/476)28.6 (164/574)0.02
Component
 1 day per week15.7 (106/675)12.1 (41/340)19.4 (65/335)0.01
 2–4 days per week35.3 (238/675)38.8 (132/340)31.6 (106/335)0.06
 ≥5 days per week49.0 (331/675)49.1 (167/340)49.0 (164/335)0.96

Association between self-reported snoring and the mean of the maximum IMT

Self-reported snorers had higher mean values of the maximum IMT of bifurcation and common carotid arteries than non-snorers. The mean value of the maximum IMT of common carotid artery in snorers was 1.03 mm (95% CI: 0.88–1.18 mm) compared with 1.00 mm (95% CI: 0.85–1.15 mm) in non-snorers (= 0.002), and that of carotid bifurcation in snorers was 1.08 mm (95% CI: 0.94–1.22 mm) compared with 1.04 mm (95% CI: 0.90–1.18 mm) in non-snorers (< 0.001). However, there was no significant difference in the mean value of the maximum IMT of internal carotid artery between snorers and non-snorers (0.67 ± 0.14 mm versus 0.66 ± 0.14 mm, = 0.25). When we categorized self-reported snorers into subgroups according to snoring frequency, we found a significant increasing trend in the mean value of the maximum IMT of carotid bifurcation with increasing snoring frequency (1.05 ± 0.13 mm on 1 day per week versus 1.07 ± 0.14 mm on 2–4 days per week versus 1.10 ± 0.13 mm on ≥5 days per week, = 0.003), but no trend differences were found in the mean values of the maximum IMT of common or internal carotid arteries (Table 3).

Table 3.   The means of maximum intima-media thickness (IMT) in common carotid, bifurcation and internal carotid arteries by self-reported snoring
VariablesThe mean of maximum IMT of common carotid artery (mm)The mean of maximum IMT of carotid bifurcation (mm)The mean of maximum IMT of internal carotid artery (mm)
Snoring
 No1.00 ± 0.151.04 ± 0.140.66 ± 0.14
 Yes1.03 ± 0.151.08 ± 0.140.67 ± 0.14
 P-value0.002<0.0010.25
Snoring frequency
 1 day per week1.01 ± 0.141.05 ± 0.130.65 ± 0.13
 2–4 days per week1.03 ± 0.151.07 ± 0.140.66 ± 0.15
 ≥5 days per week1.04 ± 0.151.10 ± 0.130.68 ± 0.14
 P-value0.100.0030.10

Association between self-reported snoring and the prevalence of carotid artery increased IMT and plaque

In the present study, we found that the prevalence of increased carotid IMT was 66.2% in self-reported snorers compared with 53.1% in non-snorers (< 0.001), and that of plaque of the common, bifurcation and internal carotid arteries was 13.6, 60.6 and 19.4% in self-reported snorers compared with 8.0, 38.9 and 14.7% in non-snorers (= 0.006, < 0.001, = 0.05). We stratified self-reported snorers into subgroups according to snoring frequency, the prevalence of increased IMT and plaque of the common, bifurcation and internal carotid arteries all increased with escalating grades of snoring frequency (Figs 1 and 2, Table S1).

image

Figure 1.  Prevalence of increased intima-media thickness (IMT) by snoring frequency and adjusted odds ratios of self-reported snoring for the presence of increased IMT.

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image

Figure 2.  Prevalence of carotid bifurcation plaque by snoring frequency and adjusted odds ratios of self-reported snoring for the presence of carotid bifurcation plaque.

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After adjustment for age, sex, smoking, alcohol intake, BMI, TG, HDL-C, LDL-C, hsCRP, hypertension and diabetes, multivariable logistic regression analysis showed that the odds of increased IMT in self-reporting habitual snorers were 1.71 times the odds in non-snorers (OR, 1.71; 95% CI: 1.22–2.39; = 0.002; Fig. 1); multiple analysis of the association between self-reported snoring and the presence of plaque showed that the odds of carotid bifurcation plaque increased with escalating grades of snoring frequency, although some of the CIs overlapped by one due to relatively small sample sizes. Compared with non-snorers, self-reported snorers who snored more than 5 days per week had the highest prevalence risk of carotid bifurcation plaque (OR, 3.63; 95% CI: 2.57–5.12; < 0.001; Fig. 2). This effect was not seen for plaque of the common or internal carotid arteries. In multivariate logistic regression analysis, current traditional risk factors measured in our study could only explain 14.8% of the variation for increased IMT and 18.3% of the variation for carotid bifurcation plaque; adding self-reported snoring variable to the model could improve this proportion to approaching 15.8% for increased IMT and 22.3% for carotid bifurcation plaque.

Discussion

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflicts of interest
  9. References
  10. Supporting Information

The present study aimed to assess the association between self-reported snoring and subclinical carotid atherosclerosis in a community-based sample of 1050 urban Chinese. The primary findings of this study are that, after adjustment for traditional cardiovascular risk factors, self-reported snoring is associated significantly with increased IMT and the presence of carotid bifurcation plaque. Moreover, both the mean values of the maximum IMT of carotid bifurcation and the prevalence of plaque were observed to increase with self-reported snoring frequency.

Many epidemiological studies have found that self-reported snoring is associated with atherosclerotic cardiovascular diseases, including stroke (D’Alessandro et al., 1990; Hu et al., 2000; Koskenvuo et al., 1987; Neau et al., 1995; Palomäki, 1991), but few epidemiological studies have assessed the association between self-reported snoring and subclinical atherosclerosis, which is the pathological basis of clinical cardiovascular and cerebrovascular events. To evaluate the possible effect of self-reported snoring on the subclinical carotid atherosclerosis, we examined the association of snoring with two measures of the carotid artery: the presence of carotid plaque and carotid IMT. Carotid plaque with or without acoustic shadowing is a marker predictive of cardiovascular and cerebrovascular events (Johnsen et al., 2007; Prati et al., 2008), whereas carotid IMT is considered to be a marker of the presence and extent of early atherosclerosis (Bonithon-Kopp et al., 1996). The current study indicated that a distinct association existed between self-reported snoring and the presence of carotid bifurcation plaque, coupled with carotid plaque as a predictor for atherosclerotic vascular accidents; therefore, we suggest that self-reported snoring screening in the general population will help in the prevention of cardiovascular and cerebrovascular diseases. In addition, we found that self-reported snoring was associated with the mean value of the maximum IMT of carotid bifurcation. This finding demonstrated that self-reported snoring may be associated with premature atherosclerosis.

A recent study in 110 patients with mild OSA and mild to heavy snoring, in which a polysomnogram was used to measure snoring, suggested that heavy snoring (snoring sleep time more than 50%) was a significant risk factor for carotid atherosclerosis (Lee et al., 2008). We conducted a population-based study on the association between self-reported snoring and carotid atherosclerosis. The current study, using self-reported information, also demonstrated that self-reported snoring, especially habitually more than 5 days per week, independent of traditional cardiovascular risk factors, was associated with carotid atherosclerosis. Thus, our findings extended the relationship between self-reported snoring and subclinical carotid atherosclerosis in the general population.

Previous studies have generally accepted that snoring as a marker of OSA is related to atherosclerotic vascular diseases (D’Alessandro et al., 1990; Koskenvuo et al., 1987; Neau et al., 1995; Palomäki, 1991). Furthermore, several reports from humans and animal models of OSA have shown consistently that OSA/intermittent hypoxia are associated independently with premature atherosclerosis in the carotid artery (Baguet et al., 2005; Drager et al., 2005; Savransky et al., 2007). According to a recent study on habitual snorers, the intensity of snoring increases as OSA becomes more severe (Maimon and Hanly, 2010). Coupled with the results from this study, we suggest that self-reported snoring, especially habitually more than 5 days per week, may be a marker of OSA associated with carotid atherosclerosis. However, we also found that those self-reported snorers who snored 2–4 days per week had a significantly higher risk for carotid bifurcation plaque compared with non-snorers, after adjustment for the traditional cardiovascular risk factors. Therefore, snoring per se may also play a direct role on carotid atherosclerosis. In addition, related mechanism studies in rabbits have confirmed that snoring vibration detected at the carotid artery wall and within the artery lumen may provide a potential energy source for carotid arterial wall damage and/or atherosclerotic plaque rupture (Amatoury et al., 2006; Howitt et al., 2007). However, the present investigation cannot exclude the relative role of OSA on carotid atherosclerosis.

OSA is a common disease, with 24% occurrence in middle-aged men and 9% in middle-aged women (Young et al., 1993), but it is usually underestimated in the general population (Kapur et al., 2002; Young et al., 1997). In contrast, snoring occurred commonly in the general population; the prevalence of self-reported snoring habitually was 31.5, and 64.3% of the participants in this study had a history of snoring. Therefore, self-reported snoring is recognized more easily by clinical doctors and the general population. Conversely, a potential limitation of this study should be addressed. The information on self-reported snoring in this study was derived from questionnaires, so some misclassification of the self-reported snoring variable was inevitable, because some participants are probably unaware of their snoring. However, as all information on self-reported snoring in this study population was collected using a validated standard questionnaire, any misclassification of self-reported snoring would be non-differential with regard to carotid artery IMT and carotid plaque which, if existing, would result in underestimation of the effects of self-reported snoring.

In conclusion, our study provides strong evidence for a high prevalence of self-reported snoring in the general population, as well as a significant relationship between self-reported snoring and the presence of carotid atherosclerosis. Hence, we feel that self-reported snoring, with or without apnoea, should be screened in the general population, which will thus assist with the early prevention of atherosclerosis and further clinical endpoint events. Moreover, we also provide subclinical evidence to support the association between self-reported snoring and atherosclerotic vascular diseases. Further studies on related mechanisms should be conducted in the future.

Acknowledgements

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflicts of interest
  9. References
  10. Supporting Information

The authors would like to thank all members of the Chinese Multi-Provincial Cohort Study research team for their support and also all researchers who participated in the field investigation. This research was supported by the Eleventh Five-Year Plan of National Support on Science and Technology in China (2006BAI01A01, 2006BAI01A02) and funding from Beijing Natural Science Foundation (7082019). The sponsors had no role in the design and conduct of the study, in the collection, management, analysis and interpretation of the data, or in the preparation, review or approval of the manuscript.

Conflicts of interest

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflicts of interest
  9. References
  10. Supporting Information

None of the authors have any conflicts of interest to declare.

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  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflicts of interest
  9. References
  10. Supporting Information
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Supporting Information

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflicts of interest
  9. References
  10. Supporting Information

Table S1. Prevalence of carotid increased intima-media thickness (IMT) and plaque by whether snore and snoring frequency and adjusted odds ratios of self-reported snoring for the presence of increased IMT and plaque.

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JSR_936_sm_TableS1.docx27KSupporting info item

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