Advertisement
Browse Subject Areas
?

Click through the PLOS taxonomy to find articles in your field.

For more information about PLOS Subject Areas, click here.

  • Loading metrics

Open Access

Peer-reviewed

Research Article

The association between autonomic dysfunction, inflammation and atherosclerosis in men under investigation for carotid plaques

  • Marcus A. Ulleryd,

    Affiliation Department of Physiology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden

    ⨯
  • Ulrica Prahl,

    Affiliation Department of Molecular and Clinical Medicine, Wallenberg Laboratory for Cardiovascular and Metabolic Research, University of Gothenburg, Sahlgrenska University Hospital, Gothenburg, Sweden

    ⨯
  • Johannes Börsbo,

    Affiliation Department of Physiology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden

    ⨯
  • Caroline Schmidt,

    Affiliation Department of Molecular and Clinical Medicine, Wallenberg Laboratory for Cardiovascular and Metabolic Research, University of Gothenburg, Sahlgrenska University Hospital, Gothenburg, Sweden

    ⨯
  • Staffan Nilsson,

    Affiliation Department of Mathematical Statistics, Chalmers University of Technology, Gothenburg, Sweden

    ⨯
  • Göran Bergström,

    Affiliation Department of Molecular and Clinical Medicine, Wallenberg Laboratory for Cardiovascular and Metabolic Research, University of Gothenburg, Sahlgrenska University Hospital, Gothenburg, Sweden

    ⨯
  • Maria E. Johansson

    maria.e.johansson@neuro.gu.se

    Affiliation Department of Physiology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden

    ⨯

Abstract

Background

Autonomic dysfunction is a risk factor for cardiovascular disease (CVD), however, the exact mechanism linking autonomic dysfunction to cardiovascular disease is not known. In this study we hypothesized that autonomic dysfunction increases inflammation, which subsequently accelerates atherosclerosis. The aim of the current study was to investigate the association between autonomic tone, inflammation and atherosclerosis.

Methods

124 men under investigation for carotid atherosclerosis were examined for autonomic function (heart rate variability; HRV and baroreflex sensitivity; BRS), inflammatory markers (white blood cell count; WBCC and C-reactive protein; CRP) and degree of carotid atherosclerosis. The direct or indirect associations between autonomic function, inflammatory parameters and carotid plaque area were investigated with multiple linear regressions.

Results

Male subjects with prevalent CVD showed larger carotid plaque area, higher WBCC, and reduced BRS compared to subjects with no history of CVD. Further, BRS was inversely associated with carotid plaque area (r = -0.21, p = 0.018) as well as inflammatory parameters WBCC and CRP (r = -0.29, p = 0.001, and r = -0.23, p = 0.009, respectively), whereas HRV only was inversely associated with WBCC (r = -0.22, p = 0.014). To investigate if inflammation could provide a link between autonomic function and carotid atherosclerosis we adjusted the associations accordingly. After adjusting for WBCC and CRP the inverse association between BRS and carotid plaque area was attenuated and did not remain significant, while both WBCC and CRP remained significantly associated with carotid plaque area, indicating that low-grade inflammation can possibly link BRS to atherosclerosis. Also, after adjusting for age, antihypertensive treatment and cardiovascular risk factors, BRS was independently inversely associated with both WBCC and CRP, and HRV independently inversely associated with WBCC. WBCC was the only inflammatory marker independently associated with carotid plaque area after adjustment.

Conclusions

We demonstrate that autonomic dysfunction is associated with atherosclerosis and that inflammation could play an important role in mediating this relationship.

Citation: Ulleryd MA, Prahl U, Börsbo J, Schmidt C, Nilsson S, Bergström G, et al. (2017) The association between autonomic dysfunction, inflammation and atherosclerosis in men under investigation for carotid plaques. PLoS ONE 12(4): e0174974. https://doi.org/10.1371/journal.pone.0174974

Editor: Christian Schulz, Ludwig-Maximilians-Universitat Munchen, GERMANY

Received: October 10, 2016; Accepted: March 19, 2017; Published: April 4, 2017

Copyright: © 2017 Ulleryd et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: Data are from the Western Region Initiative to Gather Information on Atherosclerosis (WINGA) study. Data cannot be made publicly available due to ethical restrictions. Please contact Maria Johansson (maria.e.johansson@neuro.gu.se) to request access to the data.

Funding: This work was supported by grants from The Swedish Heart Lung foundation (MJ, GB), The Swedish Research Council (MJ), The Swedish Society of Medicine (MJ), Magnus Bergvall foundation (MJ), Stiftelsen Längmanska kulturfonden (MJ), Stiftelsen Gamla tjänarinnor (MJ), Lars Hiertas foundation (MJ), Åke Wiberg foundation (MJ), OE and Edla Johanssons vetenskapliga stiftelse (MJ), Stiftelsen Tornspiran (MU), Emil and Wera Cornells stiftelse (MJ), Dr. Felix Neuberghs Foundation (MJ), Emelle Foundation (MU, MJ), Wilhelm and Martina Lundgren foundation (MU, MJ) and grants from Sahlgrenska University Hospital (ALF Agreement) (GB). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Autonomic dysfunction is associated with increased risk of cardiovascular disease (CVD) and mortality [1, 2]. Autonomic dysfunction has also been associated with increased atherosclerosis, the main underlying cause of CVD [3]. The mechanisms linking the autonomic imbalance to atherosclerosis are still elusive. Recent studies suggest an association between autonomic function and inflammation in patients with CVD, showing an inverse relationship between autonomic activity, measured by heart rate variability (HRV), and plasma levels of inflammatory markers [4–7]. HRV is a well-established and widely used approach to measure autonomic function in humans and represents the time differences between successive heartbeats [8]. However, other measures of autonomic tone like baroreflex sensitivity, assessed by analyzing the relationship between fluctuations in blood pressure and corresponding changes in RR intervals, have been poorly assessed for inflammatory associations and needs to be further investigated.

Inflammation is a key mediator in the pathophysiology of atherosclerosis involving both the innate and the adaptive immune system [9, 10]. Further, inflammatory markers such as white blood cell count (WBCC) and C-reactive protein (CRP) can predict CVD [11–13], and have been associated with atherosclerosis [14–20]. In line with this, the prevalence of CVD is known to be higher in subjects with autoimmune disorders, like systemic lupus erythematosus and rheumatoid arthritis [21, 22]. Given this background we hypothesize that inflammation can be a mediator in the link between autonomic dysfunction and atherosclerosis, leading to CVD like stroke and myocardial infarction. Few studies have investigated the whole pathway (autonomic tone—inflammation—atherosclerosis) in the same population, or measured carotid atherosclerosis as the primary end-point.

We hypothesized that reduced autonomic function will increase low-grade inflammation, subsequently worsening the progression of atherosclerosis. The aim of the current study was therefor to investigate if there is a relationship between autonomic function, assessed by both HRV and BRS, the inflammatory markers CRP and WBCC, and carotid plaque area in men undergoing investigation for carotid plaques. Further, we aimed to investigate if inflammation may be a linking mechanism between autonomic dysfunction and atherosclerosis.

Materials and methods

Study population

The participants were consecutively recruited from the “The Western Region Initiative to Gather Information on Atherosclerosis” (WINGA) population on the basis that they were males and ≥ 40 years old. The WINGA population provides patient records of all patients undergoing clinical diagnostic carotid ultrasound examinations within the Greater Gothenburg region in Sweden due to any symptoms, i.e. sudden paralysis, numbness, loss of speech, loss of vision, dizziness or severe and unusual headache. Inclusion criteria were successful assessment of autonomic function, plasma levels of C-reactive protein (CRP) ≤ 10 mg/L and white blood cell count (WBCC) ≤ 30 cells 109/L. Subjects with rheumatoid disease were excluded. Applying above mentioned criteria, a total of 124 subjects were enrolled. The study protocol conforms to the ethical guidelines of the 1975 Declaration of Helsinki and approval was obtained from the Regional Ethics Committee in Gothenburg. All patients gave written informed consent to participate.

Baseline characteristics

Subjects were invited to the laboratory and detailed clinical and life style data were collected using a standardized questionnaire. Data on anthropometry and blood pressure were collected and venous blood samples were drawn. Inflammatory status was evaluated by measuring WBCC and high-sensitivity CRP.

Measurement of carotid plaque area

Plaque area was assessed by 2D ultrasound in the common carotid artery (CCA), the carotid bulb and the proximal section of the internal carotid artery (ICA), bilaterally, as previously described [23]. Plaques were defined according to the Mannheim consensus [24]. Images were obtained of each atherosclerotic plaque and they were semi-automatically outlined and measured using a dedicated software [23]. Re-reading reproducibility of plaque size (n = 45) showed high correlation coefficients for the right and left carotid arteries (rs = 0.96 and rs = 0.96, respectively)[25].

Assessment of autonomic function

Autonomic function was assessed by measuring heart rate variability and baroreflex sensitivity in subjects.

Heart rate variability (SDNN).

A 3-lead electrocardiographic (ECG) recording was performed in supine position for 20 minutes with Biopac Pro 3.7 software (BIOPAC Systems Inc, Goleta, CA, USA). Time domain analysis on the standard deviation (SD) between normal to normal RR -intervals in the ECG-recording (SDNN) was derived with the Baro Reflex Analysis (BRA) software (Ekman Biomedical Data AB, Gothenburg, Sweden). SDNN reflects both sympathetic and parasympathetic variability during the time of recording [8].

Baroreflex sensitivity (Slope).

Continuous recordings of blood pressure were made with the sequence method [26] using The CNAP™ Monitor 500 (CNSystems Medizintechnik AG, Graz, Austria) and Biopac PRO 3.7 software (BIOPAC Systems Inc) over a period of 20 minutes with the ECG recording simultaneously. A baroreflex sequence was defined as 3 consecutive beats when the RR interval follows an increase or decrease in the systolic blood pressure, with the threshold set at 5 ms and 1 mmHg, respectively. A linear regression was applied to sequences, and correlation coefficients with r >0.92 were accepted. A mean slope was calculated from the average of qualified sequences.

A limit of 5 percent data loss in both HRV and BRS analysis was used as exclusion criteria. These kinds of data losses could be technical or biological, such as cardiac arrhythmias.

Statistics

Characteristics between different patient categories were compared using Student´s t-test for continuous variables and Chi-square test for categorical variables. Normal distribution was evaluated using Kolmogorov-Smirnov test. BRS Slope, HRV SDNN, CRP, WBCC, carotid plaque area, total cholesterol, LDL-cholesterol and HDL-cholesterol were logarithmically transformed due to skewness in distribution. However, untransformed data was presented as mean ± SD for better comparison with data from other studies.

The association between parameters for autonomic tone (HRV SDNN and BRS Slope), traditional risk factors for atherosclerosis, inflammatory markers, medical therapy and carotid plaque area were assessed with correlation (Pearson) analyses. To assess if inflammation could mediate the association between autonomic function (BRS and HRV) and carotid plaque area, multiple linear regression models with 2 predictors were used, adjusting for CRP and WBCC in separate analysis.

Independent associations between parameters for autonomic tone and inflammation, and between parameters for inflammation and atherosclerosis were assessed with multiple linear regression, adjusting for medical therapy and clinical factors. Model 1 adjusted for age. Model 2 adjusted for age and antihypertensive medicine. Model 3 was a stepwise adjustment for prevalent CVD, current smoker, BMI, diabetes, hypertension, dyslipidemia, systolic blood pressure and cholesterol-lowering medicine with a selection of p<0.05 for inclusion. Age and antihypertensive medicine were forced into the model.

The analyses were additionally stratified for treatment with statins and differences in regression slopes evaluated with an interaction term between statins and the main predictor in the model.

All data was analyzed with SPSS (IBM SPSS Statistics version 24.0, Chicago, IL, USA) and p<0.05 was considered as the level of significance.

Results

Characteristics of the study population

Analysis was carried out in 124 male subjects undergoing clinical diagnostic carotid ultrasound examinations due to any symptoms. 50% of the study subjects had prevalent CVD, defined as stroke, myocardial infarction or both. The prevalence of subjects ever diagnosed with hypertension, dyslipidemia or diabetes was 68%, 64% and 15%, respectively. The mean age was 67 years. Subject characteristics are listed in Table 1.

thumbnail
Download:
Table 1. Characteristics of study population and comparison between subjects with or without prevalent CVD.

https://doi.org/10.1371/journal.pone.0174974.t001

Comparison between subjects with prevalent CVD and subjects with no history of CVD

The study population was initially analyzed by comparing variables of inflammation, autonomic function and atherosclerosis in subjects with or without prevalent CVD (n = 62, respectively). Subjects with prevalent CVD showed decreased autonomic function, assessed with BRS Slope, increased WBCC and larger carotid plaque area, compared to subjects with no history of CVD (Table 1). However, there was no difference in plasma levels of the inflammatory marker CRP, or autonomic function assessed by HRV SDNN (Table 1). These data prompted us to expand the investigation on this interrelationship.

Relationships between autonomic function, inflammation, carotid plaque area and clinical factors

To investigate possible variables with association to carotid plaque area and inflammatory markers, univariate correlations were calculated between corresponding parameters and different clinical factors of interest (Table 2). Carotid plaque area showed a positive correlation with WBCC, CRP, age, prevalent CVD, and antihypertensive medicine whereas BRS Slope was inversely correlated with carotid plaque area. Investigating predictors of inflammation, CRP was inversely correlated with BRS Slope and positively correlated with BMI. Further, WBCC was inversely correlated with BRS Slope and HRV SDNN, and positively correlated with age, smoking, BMI, prevalent CVD and antihypertensive medicine.

thumbnail
Download:
Table 2. Relationships between parameters for autonomic function, inflammatory markers, atherosclerosis and clinical factors.

https://doi.org/10.1371/journal.pone.0174974.t002

We hypothesized that the association between BRS and atherosclerosis is dependent on inflammation. Multiple linear regression models with 2 predictors were used to investigate the direct or indirect associations between inflammatory parameters or BRS and carotid plaque area (Table 2). The analysis showed that the standardized β-coefficient for BRS Slope, adjusted for WBCC, was attenuated by 48%, and lost its significance, whereas WBCC was attenuated by 11% and still significantly associated with carotid plaque area (Table 2). Further, the standardized β-coefficient for BRS Slope, adjusted for CRP, was attenuated by 19%, and lost its significance, whereas CRP was attenuated by 18% and still significantly associated with carotid plaque area (Table 2). This suggests that low-grade inflammation could link the association between BRS Slope and carotid plaque area.

Independent relationships between reduced autonomic tone and inflammation, and inflammation and atherosclerosis

Given the data suggesting a relationship between autonomic tone and inflammation, and inflammation and atherosclerosis, we next investigated if these associations were independent of other clinical variables and medical therapy. Three different multivariable regression models were used to adjust for potential confounders. When adjusting for either age, or age and antihypertensive medicine, the inverse associations between WBCC and both BRS Slope and HRV SDNN, and the inverse association between CRP and BRS slope still remained significant (Table 3, Model 1–2). Further, the associations between carotid plaque area and both WBCC and CRP still remained significant (Table 3, Model 1–2). After adjusting for age, hypertensive medicine, prevalent CVD, current smoking, BMI, diabetes, hypertension, dyslipidemia, systolic blood pressure and cholesterol-lowering medicine these associations remained significant for all analysis except for the association between CRP and carotid plaque area (p = 0.093, Table 3, Model 3).

thumbnail
Download:
Table 3. Independent predictors of inflammation and atherosclerosis.

https://doi.org/10.1371/journal.pone.0174974.t003

When separately investigating patients on cholesterol-lowering medicine and untreated patients, the interindividual associations between inflammatory parameters, carotid plaque area and parameters for autonomic function still remained for both groups, except the association between BRS Slope or HRV SDNN and WBCC, where the association was attenuated in the untreated patients (data not shown). However, the correlations did not differ significantly between treated and untreated patients.

Discussion

This population-based study showed an inverse association between BRS and atherosclerosis and that WBCC could play an important role as a link in this relationship. Further, this study contributes with new knowledge on the independent association between autonomic function and WBCC, and between WBCC and atherosclerosis by demonstrating these relationships in the same population. Thus, this study suggests inflammation as a mediator in the relationship between reduced autonomic tone and atherosclerosis.

Autonomic dysfunction is a well-established risk factor for CVD [1–3], however the mechanisms linking autonomic tone to CVD are still unknown. Previous studies suggest a relationship between autonomic dysfunction and inflammation [4–7], as well as between inflammation and atherosclerosis [9, 10]. These findings made us hypothesize that inflammation mediates the atherogenic effects of autonomic dysfunction. Few studies have investigated the whole pathway (autonomic function—inflammation—atherosclerosis) in the same population, or carotid atherosclerosis as the primary end-point. Intima media thickness (IMT), a marker of preclinical atherosclerosis, was recently associated with increased CRP and reduced HRV in patients suffering from depression [27]. This is partly in line with the current study where we show an inverse association between autonomic function, measured by BRS, and both WBCC and established carotid plaque lesions.

The association between autonomic function and carotid plaque area could be due to direct effects of the autonomic nervous system on the progression of atherosclerosis, or mediated via other factors. To test our hypothesis that reduced autonomic function could have an impact on low-grade inflammation, which subsequently accelerates atherosclerosis, the association between BRS Slope and atherosclerosis was adjusted for the inflammatory markers WBCC and CRP. Interestingly, when adjusting for WBCC, the relationship between BRS and carotid plaque area was remarkably attenuated and no longer significant, demonstrating that WBCC could be a mechanistic link in the association between reduced BRS and carotid plaque area. However, even though adjustment for CRP also attenuates the association between reduced BRS and carotid plaque area, the role of CRP may be interpreted with care since the effect was less pronounced. Previous studies show a relationship between atherosclerosis and reduced vessel distensibility, an effect that could have an impact on autonomic function. We cannot rule out that aortic stiffness could affect autonomic function and previous studies both supports and oppose that reduced distensibility decreases BRS [28, 29]. Surprisingly, these studies rarely adjust for low-grade inflammation, known to be associated with aortic stiffness [30, 31]. Regardless of the causative direction between autonomic function and atherosclerosis, our data demonstrate that inflammation could play a role in this pathway.

Given that inflammatory markers might mediate the association between BRS and carotid plaque area, we next investigate if autonomic function was independently associated with inflammatory markers WBCC and CRP, and subsequently, if WBCC and CRP was independently associated with carotid plaque area. The hypothesis of inflammation as a mechanistic link between autonomic dysfunction and atherosclerosis derives from a number of different studies displaying an inverse association between HRV and inflammatory markers, in both patients with CVD [4–7], and in populations without CVD [32–36]. We confirm these relationships, demonstrating an association between HRV and WBCC in the current study. This relationship is also extended by including another marker of autonomic function, BRS, also demonstrating an independent association with both WBCC and CRP. In the current study, only CRP and WBCC were used to assess inflammation. Given the perplexity of the inflammatory process in atherosclerosis other inflammatory markers, such as cytokines, should be further evaluated in future studies.

The relationship between inflammatory markers and CVD has been thoroughly characterized in previous studies. WBCC, a low-grade inflammatory marker has been an independent predictor of CVD [12, 13], and associated with increased intima media thickness (IMT), as well as femoral and carotid atherosclerosis [14–17]. Our results support these findings, showing an association between WBCC and carotid plaque area, independent of other cardiovascular risk factors. Although, a large number of studies show CRP to be a strong predictor for CVD [11] this association did not remain significant after adjusting for age, hypertensive medicine and other clinical risk factors in the current study. The role of CRP as an independent predictor of the extent of atherosclerosis is debated, where some studies support this [18–20], while other studies do not [14, 37, 38]. It is possible that the relationship between CRP and CVD is more associated to the phenotype of atherosclerotic plaques [39–41], rather than the extent, which is the focus in the current study. Still, our results on inflammation and atherosclerosis confirm previous studies where carotid atherosclerosis was independently associated with WBCC but not CRP [14].

Since cholesterol-lowering treatments influence both inflammation [42, 43], and atherosclerosis [44, 45], a sensitivity analysis for cholesterol-lowering treatment was conducted. Although, most of the associations were coherent with the relationships in the whole population, the fully adjusted associations between BRS Slope or HRV SDNN and WBCC were reduced in the untreated patients (data not shown). However, the correlation in this smaller group did not differ significantly from the treated group so the lack of association is possibly due to lack of power.

In summary, in this study, men with prevalent CVD have reduced BRS, increased WBCC and more carotid atherosclerosis compared to male subjects with no history of previous CVD. We demonstrate that autonomic function is associated with atherosclerosis and that inflammation could play an important role in mediating this relationship. Although this study demonstrates that there is a relationship between autonomic dysfunction, inflammation and atherosclerosis, the causal relationship between these parameters remains to be determined.

Author Contributions

  1. Conceptualization: MU GB MJ.
  2. Data curation: MU JB.
  3. Formal analysis: MU GB MJ SN JB.
  4. Funding acquisition: MJ MU GB.
  5. Investigation: UP CS.
  6. Methodology: MU GB MJ.
  7. Project administration: GB MJ.
  8. Resources: GB MJ.
  9. Supervision: MJ GB.
  10. Validation: MU MJ.
  11. Visualization: MU MJ.
  12. Writing – original draft: MU MJ GB.
  13. Writing – review & editing: MU MJ GB SN CS UP JB.

References

  1. 1. Kleiger RE, Miller JP, Bigger JT Jr, Moss AJ. Decreased heart rate variability and its association with increased mortality after acute myocardial infarction. Am J Cardiol. 1987;59(4):256–62. Epub 1987/02/01. pmid:3812275
  2. 2. Tsuji H, Larson MG, Venditti FJ Jr, Manders ES, Evans JC, Feldman CL, et al. Impact of reduced heart rate variability on risk for cardiac events. The Framingham Heart Study. Circulation. 1996;94(11):2850–5. Epub 1996/12/01. pmid:8941112
  3. 3. Huikuri HV, Jokinen V, Syvanne M, Nieminen MS, Airaksinen KE, Ikaheimo MJ, et al. Heart rate variability and progression of coronary atherosclerosis. Arterioscler Thromb Vasc Biol. 1999;19(8):1979–85. Epub 1999/08/14. pmid:10446081
  4. 4. Aronson D, Mittleman MA, Burger AJ. Interleukin-6 levels are inversely correlated with heart rate variability in patients with decompensated heart failure. J Cardiovasc Electrophysiol. 2001;12(3):294–300. Epub 2001/04/09. pmid:11291801
  5. 5. Hamaad A, Sosin M, Blann AD, Patel J, Lip GY, MacFadyen RJ. Markers of inflammation in acute coronary syndromes: association with increased heart rate and reductions in heart rate variability. Clin Cardiol. 2005;28(12):570–6. Epub 2006/01/13. pmid:16405201
  6. 6. Janszky I, Ericson M, Lekander M, Blom M, Buhlin K, Georgiades A, et al. Inflammatory markers and heart rate variability in women with coronary heart disease. J Intern Med. 2004;256(5):421–8. Epub 2004/10/16. pmid:15485478
  7. 7. Lanza GA, Sgueglia GA, Cianflone D, Rebuzzi AG, Angeloni G, Sestito A, et al. Relation of heart rate variability to serum levels of C-reactive protein in patients with unstable angina pectoris. Am J Cardiol. 2006;97(12):1702–6. Epub 2006/06/13. pmid:16765117
  8. 8. Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Heart rate variability: standards of measurement, physiological interpretation and clinical use. Circulation. 1996;93(5):1043–65. Epub 1996/03/01.
  9. 9. Libby P, Ridker PM. Inflammation and AtherothrombosisFrom Population Biology and Bench Research to Clinical Practice. J Am Coll Cardiol. 2006;48(9s1):A33–A46.
  10. 10. Hansson GK. Inflammation, Atherosclerosis, and Coronary Artery Disease. N Engl J Med. 2005;352(16):1685–95. pmid:15843671
  11. 11. Musunuru K, Kral BG, Blumenthal RS, Fuster V, Campbell CY, Gluckman TJ, et al. The use of high-sensitivity assays for C-reactive protein in clinical practice. Nat Clin Pract Cardiovasc Med. 2008;5(10):621–35. Epub 2008/08/20. pmid:18711404
  12. 12. Weijenberg MP, Feskens EJM, Kromhout D. White Blood Cell Count and the Risk of Coronary Heart Disease and All-Cause Mortality in Elderly Men. Arterioscler Thromb Vasc Biol. 1996;16(4):499–503. pmid:8624770
  13. 13. Kannel WB, Anderson K, Wilson PW. White blood cell count and cardiovascular disease. Insights from the Framingham Study. JAMA. 1992;267(9):1253–6. Epub 1992/03/04. pmid:1538564
  14. 14. Ortega E, Gilabert R, Nunez I, Cofan M, Sala-Vila A, de Groot E, et al. White blood cell count is associated with carotid and femoral atherosclerosis. Atherosclerosis. 2012;221(1):275–81. Epub 2012/01/17. pmid:22244768
  15. 15. Huang ZS, Jeng JS, Wang CH, Yip PK, Wu TH, Lee TK. Correlations between peripheral differential leukocyte counts and carotid atherosclerosis in non-smokers. Atherosclerosis. 2001;158(2):431–6. Epub 2001/10/05. pmid:11583723
  16. 16. Loimaala A, Rontu R, Vuori I, Mercuri M, Lehtimaki T, Nenonen A, et al. Blood leukocyte count is a risk factor for intima-media thickening and subclinical carotid atherosclerosis in middle-aged men. Atherosclerosis. 2006;188(2):363–9. Epub 2005/12/28. pmid:16378612
  17. 17. Temelkova-Kurktschiev T, Koehler C, Henkel E, Hanefeld M. Leukocyte count and fibrinogen are associated with carotid and femoral intima-media thickness in a risk population for diabetes. Cardiovasc Res. 2002;56(2):277–83. Epub 2002/10/24. pmid:12393098
  18. 18. Elias-Smale SE, Kardys I, Oudkerk M, Hofman A, Witteman JC. C-reactive protein is related to extent and progression of coronary and extra-coronary atherosclerosis; results from the Rotterdam study. Atherosclerosis. 2007;195(2):e195–202. Epub 2007/08/24. pmid:17714718
  19. 19. Blackburn R, Giral P, Bruckert E, Andre JM, Gonbert S, Bernard M, et al. Elevated C-reactive protein constitutes an independent predictor of advanced carotid plaques in dyslipidemic subjects. Arterioscler Thromb Vasc Biol. 2001;21(12):1962–8. Epub 2001/12/18. pmid:11742871
  20. 20. Alizadeh Dehnavi R, Beishuizen ED, van de Ree MA, Le Cessie S, Huisman MV, Kluft C, et al. The impact of metabolic syndrome and CRP on vascular phenotype in type 2 diabetes mellitus. Eur J Intern Med. 2008;19(2):115–21. Epub 2008/02/06. pmid:18249307
  21. 21. Frostegard J. Atherosclerosis in patients with autoimmune disorders. Arterioscler Thromb Vasc Biol. 2005;25(9):1776–85. Epub 2005/06/25. pmid:15976324
  22. 22. Manzi S, Meilahn EN, Rairie JE, Conte CG, Medsger TA Jr, Jansen-McWilliams L, et al. Age-specific incidence rates of myocardial infarction and angina in women with systemic lupus erythematosus: comparison with the Framingham Study. Am J Epidemiol. 1997;145(5):408–15. Epub 1997/03/01. pmid:9048514
  23. 23. Hjelmgren O, Holdfeldt P, Johansson L, Fagerberg B, Prahl U, Schmidt C, et al. Identification of vascularised carotid plaques using a standardised and reproducible technique to measure ultrasound contrast uptake. Eur J Vasc Endovasc Surg. 2013;46(1):21–8. Epub 2013/04/27. pmid:23619371
  24. 24. Touboul PJ, Hennerici MG, Meairs S, Adams H, Amarenco P, Bornstein N, et al. Mannheim carotid intima-media thickness and plaque consensus (2004-2006-2011). An update on behalf of the advisory board of the 3rd, 4th and 5th watching the risk symposia, at the 13th, 15th and 20th European Stroke Conferences, Mannheim, Germany, 2004, Brussels, Belgium, 2006, and Hamburg, Germany, 2011. Cerebrovasc Dis. 2012;34(4):290–6. Epub 2012/11/07. pmid:23128470
  25. 25. Wallenfeldt K, Hulthe J, Bokemark L, Wikstrand J, Fagerberg B. Carotid and femoral atherosclerosis, cardiovascular risk factors and C-reactive protein in relation to smokeless tobacco use or smoking in 58-year-old men. J Intern Med. 2001;250(6):492–501. pmid:11902817
  26. 26. Bertinieri G, di Rienzo M, Cavallazzi A, Ferrari AU, Pedotti A, Mancia G. A new approach to analysis of the arterial baroreflex. J Hypertens Suppl. 1985;3(3):S79–81. Epub 1985/12/01. pmid:2856787
  27. 27. Pizzi C, Manzoli L, Mancini S, Bedetti G, Fontana F, Costa GM. Autonomic nervous system, inflammation and preclinical carotid atherosclerosis in depressed subjects with coronary risk factors. Atherosclerosis. 2010;212(1):292–8. Epub 2010/06/01. pmid:20510416
  28. 28. Eiken O, Nowak J, Jogestrand T, Mekjavic IB. Effects of local arteriosclerosis on carotid baroreflex sensitivity and on heart rate and arterial pressure variability in humans. Clin Physiol Funct Imaging. 2006;26(1):9–14. Epub 2006/01/10. pmid:16398664
  29. 29. Nasr N, Pavy-Le Traon A, Larrue V. Baroreflex sensitivity is impaired in bilateral carotid atherosclerosis. Stroke. 2005;36(9):1891–5. Epub 2005/08/16. pmid:16100025
  30. 30. Wakabayashi I, Masuda H. Association of acute-phase reactants with arterial stiffness in patients with type 2 diabetes mellitus. Clin Chim Acta. 2006;365(1–2):230–5. Epub 2005/10/04. pmid:16199026
  31. 31. Papazafiropoulou A, Tentolouris N, Moyssakis I, Perrea D, Katsilambros N. The Potential Effect of Some Newer Risk Factors for Atherosclerosis on Aortic Distensibility in Subjects With and Without Type 2 Diabetes. Diabetes Care. 2006;29(8):1926–8. pmid:16873806
  32. 32. Araujo F, Antelmi I, Pereira AC, Latorre Mdo R, Grupi CJ, Krieger JE, et al. Lower heart rate variability is associated with higher serum high-sensitivity C-reactive protein concentration in healthy individuals aged 46 years or more. Int J Cardiol. 2006;107(3):333–7. Epub 2006/03/01. pmid:16503254
  33. 33. Cooper TM, McKinley PS, Seeman TE, Choo TH, Lee S, Sloan RP. Heart rate variability predicts levels of inflammatory markers: Evidence for the vagal anti-inflammatory pathway. Brain Behav Immun. 2015;49:94–100. Epub 2014/12/30. pmid:25541185
  34. 34. Lampert R, Bremner JD, Su S, Miller A, Lee F, Cheema F, et al. Decreased heart rate variability is associated with higher levels of inflammation in middle-aged men. Am Heart J. 2008;156(4):759 e1–7. Epub 2008/10/18.
  35. 35. Sajadieh A, Nielsen OW, Rasmussen V, Hein HO, Abedini S, Hansen JF. Increased heart rate and reduced heart-rate variability are associated with subclinical inflammation in middle-aged and elderly subjects with no apparent heart disease. Eur Heart J. 2004;25(5):363–70. Epub 2004/03/23. pmid:15033247
  36. 36. Stein PK, Barzilay JI, Chaves PH, Traber J, Domitrovich PP, Heckbert SR, et al. Higher levels of inflammation factors and greater insulin resistance are independently associated with higher heart rate and lower heart rate variability in normoglycemic older individuals: the Cardiovascular Health Study. J Am Geriatr Soc. 2008;56(2):315–21. Epub 2008/01/09. pmid:18179502
  37. 37. Hunt ME, O'Malley PG, Vernalis MN, Feuerstein IM, Taylor AJ. C-reactive protein is not associated with the presence or extent of calcified subclinical atherosclerosis. Am Heart J. 2001;141(2):206–10. Epub 2001/02/15. pmid:11174333
  38. 38. Folsom AR, Pankow JS, Tracy RP, Arnett DK, Peacock JM, Hong Y, et al. Association of C-reactive protein with markers of prevalent atherosclerotic disease. Am J Cardiol. 2001;88(2):112–7. Epub 2001/07/13. pmid:11448405
  39. 39. Williams TN, Zhang CX, Game BA, He L, Huang Y. C-reactive protein stimulates MMP-1 expression in U937 histiocytes through Fc[gamma]RII and extracellular signal-regulated kinase pathway:: an implication of CRP involvement in plaque destabilization. Arterioscler Thromb Vasc Biol. 2004;24(1):61–6. Epub 2003/11/01. pmid:14592848
  40. 40. Burke AP, Tracy RP, Kolodgie F, Malcom GT, Zieske A, Kutys R, et al. Elevated C-Reactive Protein Values and Atherosclerosis in Sudden Coronary Death: Association With Different Pathologies. Circulation. 2002;105(17):2019–23. pmid:11980679
  41. 41. Verma S, Li S-H, Badiwala MV, Weisel RD, Fedak PWM, Li R-K, et al. Endothelin Antagonism and Interleukin-6 Inhibition Attenuate the Proatherogenic Effects of C-Reactive Protein. Circulation. 2002;105(16):1890–6. pmid:11997273
  42. 42. Ascer E, Bertolami MC, Venturinelli ML, Buccheri V, Souza J, Nicolau JC, et al. Atorvastatin reduces proinflammatory markers in hypercholesterolemic patients. Atherosclerosis. 2004;177(1):161–6. Epub 2004/10/19. pmid:15488879
  43. 43. van de Ree MA, Huisman MV, Princen HM, Meinders AE, Kluft C. Strong decrease of high sensitivity C-reactive protein with high-dose atorvastatin in patients with type 2 diabetes mellitus. Atherosclerosis. 2003;166(1):129–35. Epub 2002/12/17. pmid:12482559
  44. 44. Lima JA, Desai MY, Steen H, Warren WP, Gautam S, Lai S. Statin-induced cholesterol lowering and plaque regression after 6 months of magnetic resonance imaging-monitored therapy. Circulation. 2004;110(16):2336–41. Epub 2004/10/13. pmid:15477398
  45. 45. Herder M, Arntzen KA, Johnsen SH, Eggen AE, Mathiesen EB. Long-Term Use of Lipid-Lowering Drugs Slows Progression of Carotid Atherosclerosis. The Tromsø Study 1994 to 2008. 2013;33(4):858–62.