| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(Stroke. 1999;30:299-305.)
© 1999 American Heart Association, Inc.
Original Contributions |
Chlamydia pneumoniae but Not Cytomegalovirus Antibodies Are Associated With Future Risk of Stroke and Cardiovascular Disease
A Prospective Study in Middle-Aged to Elderly Men With Treated Hypertension
From the Department of Medicine, Sahlgrenska University Hospital (B.F., S.A.), Göteborg; Department of Clinical Microbiology, Gävle Central Hospital (J.G., H.G.), Gävle; Institute of Infectious Diseases and Clinical Microbiology, University of Uppsala (H.G.), Uppsala; and Wallenberg Laboratory for Cardiovascular Research, Göteborg University (J.W.), Göteborg, Sweden.
Correspondence to Dr Björn Fagerberg, Department of Medicine, Sahlgrenska University Hospital, S-413 45 Göteborg, Sweden. E-mail bjorn.fagerberg{at}mailer.mednet.gu.se
 |
Abstract |
|---|
 Top Abstract IntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
Background and Purpose—Several cross-sectional and prospective studies have indicated that high titers of antibodies to Chlamydia pneumoniae and cytomegalovirus (CMV) are associated with coronary heart disease. The aim of the present study was to examine whether elevated titers of antibodies to these pathogens are predictive of not only coronary but also cerebrovascular disease.
Methods—Serum titers of antibodies to C pneumoniae (IgM, IgG, IgA, IgG immune complex) and CMV (IgG) were determined at baseline (n=130) and after 3.5 years (n=111) in a total sample of 152 men. All individuals had treated hypertension and at least 1 additional risk factor for cardiovascular disease (hypercholesterolemia, smoking, or diabetes mellitus) and constituted 93% of a randomly selected subgroup (n=164) of patients participating in a multiple risk factor intervention study.
Results—Elevations of any or both of the IgA or IgG titers to C pneumoniae at entry or after 3.5 years were found in 84 cases (55%). Of those with high titers at entry, 97% remained high at the 3.5 year reexamination. After 6.5 years of follow-up, high titers to C pneumoniae at entry were associated with an increased risk for future stroke (relative risk [RR], 8.58; P=0.043; 95% CI, 1.07 to 68.82) and for any cardiovascular event (RR, 2.69; P=0.042; 95% CI, 1.04 to 6.97). A high serum titer of antibodies to CMV was found in 125 cases (85%), and this was not associated with an increased risk of future cardiovascular events.
Conclusions—Seropositivity for C pneumoniae, but not for CMV, was associated with an increased risk for future cardiovascular disease and, in particular, stroke.
Key Words: cerebrovascular disorders • cardiovascular diseases • Chlamydia pneumoniae • prospective studies
|
Introduction |
|---|
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
There is an accumulating amount of data indicating that infections may be linked to atherosclerotic disease. There are also a number of potential underlying mechanisms for such an association that may be of a causative nature. Infection may both augment the atherosclerotic process and contribute to later manifestations of overt clinical disease by facilitating plaque rupture and thrombosis.1
Chlamydia pneumoniae TWAR is an intracellular gram-negative bacterium that commonly causes respiratory infections in all age groups.2 The clinical picture varies from asymptomatic infection or unrecognized, mildly symptomatic disease to bronchitis and pneumonia. Specific antibodies to C pneumoniae have been found in more than half of the adult population.3 Persistent infection is not uncommon after acute respiratory infection with C pneumoniae.4 A recent meta-analysis indicated that available data support the hypothesis that C pneumoniae may be causative for arterial disease, although further research is needed.1
The cytomegaloviruses (CMVs) are a subgroup of agents closely related to the herpes group of viruses. The cytomegaloviruses are ubiquitous, and the incidence of infection gradually increases with age: 60% to 90% of adults have experienced infection.5 CMV infection may be acquired transplacentally, during birth, or by contact with infected secretions or excretions at any time thereafter. Infections acquired postnatally or later in life are often asymptomatic but may appear as an acute febrile illness, termed cytomegalovirus mononucleosis or hepatitis, depending on the clinical picture. A more fulminant severe disease may develop in patients with a compromised immunological system.
CMV is also suggested as an infectious agent of importance for the atherosclerotic disease process.1 However, only a limited number of patients with classic atherosclerotic heart disease have been examined for CMV.
Although most studies have been focused on coronary heart disease, there have also been reports on associations between infection and cerebrovascular disease.6 7 8 9 Most of the published reports have been based on cross-sectional studies, and there is a need for more prospective studies.
The Risk Factor Intervention study was a prospective, randomized study that examined whether a dedicated program aimed at lowering lipids and cessation of smoking, in addition to antihypertensive treatment, would improve the prognosis compared with usual care.10 11 All patients were men with treated hypertension and at least 1 of the risk factors hypercholesterolemia, smoking, or diabetes mellitus. The follow-up period was >6 years. Frozen serum samples from this study were used to test the hypothesis that high titers of antibodies to C pneumoniae and CMV were associated with future cardiovascular disease.
|
Subjects and Methods |
|---|
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
Study Outline and Patients
Five hundred eight male patients with treated primary hypertension were included in a risk factor intervention study10 11 The inclusion criteria for the intervention study were, apart from treated hypertension and male sex, 1 or more of the following: hypercholesterolemia (serum cholesterol of
6.5 mmol/L), tobacco smoking (1
cigarettes/d), or diabetes mellitus (fasting blood glucose of >7
mmol/L).10 11 The patients were
representative of high-risk hypertensives in
Gothenburg, since the majority (>90%) were recruited by randomly
screening one third of all men in the respective age groups in
Gothenburg.10 11 In the aforementioned intervention study,
the patients had been randomized either to a multiple risk-factor
treatment program or to conventional treatment. The intervention
program was based on a nonpharmacological and, if necessary,
pharmacological regimen aimed at lowering
hypercholesterolemia and cessation of
smoking.
From this group of 508 men, one third of the patients were randomly
selected to take part in substudies on the development of
atherosclerosis as assessed by ultrasound examinations
of the carotid arteries, and blood was drawn for a number of
biochemical assessments.12 13 In this group of 164
patients, serum samples for serological analysis were available
for 130 patients at entry. After 3.5 years of follow-up (median) in the
intervention study, sera from 111 patients were available for
analyses. In total, 152 patients were included in the
present study, and serological analyses were performed at
entry as well as after 3.5 years in 89 patients (Figure 1
).
|
All men gave informed consent after written and oral information, and the study was approved by the ethics committee of the Faculty of Medicine, Göteborg University, Göteborg, Sweden.
Measurements
Resting blood pressure was measured phonographically
(Korotkoff sounds recorded on ECG paper) in the right arm after
supine rest in connection with the ultrasound examination, as described
previously.10 Blood pressure was calculated to the nearest
1 mm Hg, and the mean of 2 recordings was used. Body
weight and body mass index were measured according to established
principles.10 Smoking was assessed with a
questionnaire.10 Cigarette-years were calculated as the
number of years as a smoker times the average number of smoked
cigarettes. Manifest cardiovascular disease was defined
as the presence of one or more of the following diagnoses: stroke,
myocardial infarction, angina pectoris, or intermittent
claudication.10 11
Venous blood was drawn after an overnight fast and after 5 minutes of supine rest for the determination of blood glucose, serum levels of triglycerides, and total and HDL cholesterol by established methods.10 11 Serum aliquots were frozen initially at -20°C and were later kept at -70°C until the serological assays were performed.
End Points
No patient was lost to follow-up. All fatal and nonfatal events
were independently coded by 2 physicians who did not participate in the
study and who had no knowledge of patient identity or the group
assignment in the study.11 Copies of hospital
records, autopsy records, and death certificates were
available. The diagnostic criteria have been described
previously.10 11 Cardiovascular mortality
was defined as any of the following diagnoses: myocardial infarction,
sudden death, fatal stroke, progressive cardiac failure, ruptured
aortic aneurysm, or other cardiovascular death
(no obvious noncardiovascular cause of death). Any
cardiovascular event was defined as
cardiovascular death as described above, nonfatal
myocardial infarction, or nonfatal stroke. The median follow-up time
was 6.5 years (range, 0.2 to 7.5 years).
Serological Analyses
The analysis of the antibodies to C
pneumoniae was performed with use of a modified
microimmunofluorescence technique. Sera were
diluted 1:32 in PBS, pH 7.4, and tested for IgG, IgA, and IgM
antibodies on 21-well antigen slides containing elementary body
preparations of Chlamydia psittaci, C pneumoniae,
and Chlamydia trachomatis in each well (Laboratory Systems
Oy). Sera that were positive in screening tests for IgG were
rediluted and tested in doubling dilutions. Sera positive in screening
tests for IgA and/or IgM were absorbed with Gullsorb (Gull
Laboratories) at a dilution of 1:16 to remove all
IgG,14 then titrated in doubling dilutions with PBS.
Serum dilutions were incubated with antigen slides for 14 to 16 hours
at 4°C to 8°C, after which slides were gently agitated in three
5-minute changes of PBS and air dried. Fluorescein
isothiocyanate conjugated rabbit anti-human IgG, IgA or IgM (Dakopatts)
was applied to appropriate wells and incubation was done for 30 minutes
at 37°C. After a renewed washing procedure with three 5-minute
changes of PBS, slides were immersed in H2O for 2
minutes and air dried. Coverslips were mounted with buffered glycerol,
and slides were read in a Zeiss UV microscope with a x40 oil immersion
lens and a x10 ocular lens (total magnification, x400). All slides
were read by the same investigator, who was unaware of the
case-reference status of the sera or any clinical characteristics of
the patients. Control sera routinely used in the laboratory was
included in every test run, and tests were accepted only if the control
sera titers were within 1 titer step of the earlier calculated mean.
The last dilution step to give specific fluorescence was
reported as the reciprocal titer. Based on Grayston's
suggestions2 and on earlier experiences,3 15
a reciprocal IgG titer of 512 and/or an IgA titer of 64 were used
as lower limits for positive serology.
All serum specimens were investigated for complex-bound IgG antibody to
C pneumoniae (IC) after treatment of the serum sample with
7% PEG 6000 (Janssen Chimica).16 Equal parts of sera
and PEG were mixed, left overnight at 4°C, and centrifuged
the next day. Pellets obtained were resuspended and washed twice with
3.5% PEG, then finally resuspended in PBS, pH 7.2, to the same volume
as the original serum aliquot. The resuspended specimens were then
diluted 1:2 with PBS and tested for C pneumoniae IgG
antibodies with use of the species-specific
microimmunofluorescence technique. All antibody
tests were read with a Zeiss UV microscope with a plane achromatic oil
immersion lens at a final magnification of x400. High titers of
circulating immune complexes were arbitrarily defined as a reciprocal
titer of 8.
IgG antibodies to cytomegalovirus were determined by use of a
microparticle enzyme immunoassay technique (AxSYM CMV IgG, Abbot
Laboratories). Sera were loaded into cups, which were placed in the
AxSYM unit and processed according to manufacturer's instructions. All
sera with particulate matter or cells were first centrifuged to
remove debris. Reciprocal IgG antibody titers are expressed as
arbitrary units (AU) per milliliter, where 15.0 AU/mL is considered a
positive result. Sera with titers of 250 AU/mL, the limit of the
system, were not diluted and retested.
Statistical Analyses
Defined end points in the study were
cardiovascular death, fatal and nonfatal myocardial
infarction, fatal and nonfatal stroke, and other
cardiovascular disease, as previously defined. All
first cardiovascular events were also used as a
combined end point.
Poisson models were used in a hazard function for outcome that was
 |
The model was also used to calculate the probability of stroke or any
cardiovascular event occurring within 5 years, provided
that the individual patient was followed up during the observation
period or up to the time of the event. The examples
represent patients who were not current smokers, who had no
previous cardiovascular disease, and who had been
randomized to the control group in the underlying risk factor
intervention study (Figure 2).
|
The Student's t test was used for comparison of continuous variables, and the Spearman rank correlation coefficient was used for the correlation analyses. The results are given as means and standard deviations, or as number (%) if nothing else is indicated. A 2-sided value of P<0.05 was regarded as statistically significant.
|
Results |
|---|
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
The patients with high titers to C pneumoniae did not show any characteristics that were statistically different from those of patients with no antibodies or low titers, either at entry or at the examination after 3.5 years (Tables 1
and 2). Higher titers of circulating immune
complex were found in the groups with high antibody titers.
|
|
C pneumoniae Serology
High titers of IgA and/or IgG antibodies to C
pneumoniae at both or either examinations at entry or after 3.5
years were found in 84 cases (55%). The titers of IgA and IgG
antibodies to C pneumoniae were interrelated both at entry
(rs=0.67, P<0.001) and at the
3.5-year examination (rs=0.59,
P<0.001), and a high or low titer of IgG antibody was in
general accompanied by a similar level in the concentration of IgA
antibody (Table 3). The IgG antibodies
demonstrated a close correlation to the immune complex level both at
entry (rs=0.77, P<0.001) and
after 3.5 years (rs=0.73,
P<0.001). The IgM antibody titer was elevated in only 1
patient, both at the first and second examinations. No cross-reactions
were seen between C pneumoniae and the other
Chlamydia species.
|
As shown in Table 4, high titers of IgG
or IgA antibodies to C pneumoniae at entry was associated
with titers remaining high after 3.5 years. Among the 89
patients with measurements available at both entry and reexamination,
38 patients had high IgA and/or IgG titer at entry. High titers,
according to this definition, remained high in 37 (97%) of these 38
men.
|
CMV Serology
Seropositivity to CMV at both or either examinations,
at entry or after 3.5 years, was found in 125 cases (85%). There was
no association between high titers of CMV antibodies and high titers of
C pneumoniae antibodies (data not shown).
Clinical Outcome
The clinical outcome during 6.5 years of follow-up in relation to
C pneumoniae antibody levels is presented in Table 5. In the group with low antibody
titers, there was 1 case of hemorrhagic stroke and 1 case of
ischemic stroke, whereas the corresponding numbers in the high
titer group were 2 and 8, respectively. In addition, there was 1
patient with no available CT brain scan after the event in the
high-titer group.
|
As shown in Table 6 and Figure 1
, high titers of antibodies to C
pneumoniae were associated with significantly increased risks for
future stroke or the occurrence of any cardiovascular
event (RRs of 8.58 and 2.69, respectively) after adjustment for
previous cardiovascular disease, for smoking, and for
group allocation in the underlying multiple risk factor intervention
study. Similarly, a high titer of circulating immune complex was
associated with a borderline significant RR (3.61) of future stroke
(P=0.053; 95% CI, 0.98 to 13.27), whereas the corresponding
risk for any cardiovacular event was 2.09 (P=0.10; 95% CI,
0.88 to 4.98).
|
A high titer of antibodies to CMV was not associated with future stroke
or any cardiovascular event, and the relative risk of
cardiovascular death was reduced (Table 7).
|
|
Discussion |
|---|
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
The results from this prospective study of treated hypertensive men indicate that high titers of circulating antibodies to C pneumoniae, but not CMV, are associated with increased risks for future stroke or the combined end point of cardiovascular events such as fatal or nonfatal stroke or myocardial infarction (time to first event). However, this is an observation based on serological analyses of frozen serum samples obtained within the frame of a previous multiple risk factor intervention study,10 11 12 13 and there are a number of methodological issues to address.
It may be difficult to obtain relevant information on the persistence of an infectious agent by use of serological tests.1 Various combinations of antibody fractions and various cut-off titers to define C pneumoniae seropositivity have been used in previous studies.1 We used predefined cut-off limits based on results from several studies,2 3 15 including studies that have related seropositivity to other evidence of active chronic C pneumoniae infection.18 19 20 21 Both IgA and IgG antibodies were used because they confer complementary information on the host–C pneumoniae interaction: some patients do not respond to C pneumoniae infection with specific antibodies of both the IgG and IgA classes.19 20 21 The reason for this is not known. The results demonstrated that both elevated IgA and IgG titers remained high after a median follow-up period of several years. By analyzing duplicate serum samples obtained with an interval of several years, we also had the opportunity to examine whether the suggested decision limits were associated with evidence of a persistent infection, as indicated by stable high titers. This was the case, because 97% of the patients who had either or both of the IgA or IgG antibody titers elevated at entry had persistent high levels at the reexamination. In addition, the patients with high titers also had high levels of circulating immune complexes, containing C pneumoniae protein antigen, indicating the presence of the bacterium. High titers of circulating immune complex were also associated with an RR of 3.61 (95% CI, 0.98 to 13.27) for future stroke. Only 1 patient had raised IgM titers as evidence of recent infection. Thus, it seems reasonable to assume that patients with high titers of either or both IgA and IgG antibodies suffered from a chronic C pneumoniae infection.
Our results may have been biased by uncontrolled effects of other risk factors. However, the patients with high and low antibody titers to C pneumoniae did not differ in any obvious aspect, and the analysis of final outcome was adjusted for smoking status, previous cardiovascular disease, and group assignment in the underlying multiple risk intervention study. In terms of the association between seropositivity for C pneumoniae and risk factors for cardiovascular disease, only smoking has shown a covariability.22 23 24 Varying results have been reported for hypertension and dyslipidemia.4 25 26 27
Is it possible to generalize our results? The study population consisted of middle-aged to elderly men with treated hypertension and the presence of at least 1 additional risk factor for cardiovascular disease, resulting in a high morbidity and mortality risk.11 As previously described, the patients were originally recruited from a randomly selected population sample and may therefore be representative of elderly hypertensive men at high risk.10 11 12 13
A chronic C pneumoniae infection was found in more than half of the patients investigated, and infection was associated with a substantially increased risk of future cardiovascular disease, stroke in particular. The limited sample size makes the CIs very wide, but RR =8.58 for stroke and RR=2.69 for any cardiovascular event support the conclusion of a recent meta-analysis1 that C pneumoniae may be a causative factor in arterial disease, although this is still unproved.
Previous studies have dealt mainly with coronary heart disease and have in most cases been based on cross-sectional designs.1 There are only a few prospective studies, but these have indicated an association between seropositivity to C pneumoniae and coronary heart disease.4 24 28 A few cross-sectional studies showing a relationship between carotid atherosclerosis, carotid stenosis, stroke, TIA, and seropositivity to C pneumoniae have been published.6 7 8 To our knowledge, there is no previous prospective study demonstrating that chronic C pneumoniae infection may be associated with an increased risk of stroke.
Although the incidence of coronary heart disease was higher than the incidence of stroke in the present study, seropositivity for C pneumoniae was not associated with a significantly increased risk for cardiovascular death (RR=1.15; 95% CI, 0.22 to 5.99) or myocardial infarction (RR=1.52; 95% CI, 0.48 to 4.78), whereas it emerged as a significant predictor for stroke or any cardiovascular event. However, the CIs for the relative risks of cardiovascular mortality and myocardial infarction found in this study seem to agree with the corresponding results reported in previous studies.1 Our observation that seropositivity for C pneumoniae may be a better risk marker for stroke than for coronary heart disease cannot be compared with previous experiences, because no similar studies have been performed.
Given the high frequency of positive C pneumoniae serology, the results from the present and previous studies indicate that a persistent C pneumoniae infection might be a common and very powerful risk factor for vascular disease, comparable in magnitude with the classic risk factors. The underlying pathophysiological mechanisms are largely unknown, but both effects on plaque growth and plaque rupture with subsequent thrombosis formation have been suggested.1 There are a number of observations giving support to these hypotheses. Thus, experimental C pneumoniae infection has been shown to induce vascular infection and contribute to the development of the atherosclerotic process.1 29 30 In 13 studies of cardiovascular tissues, local C pneumoniae infection was found in 52% of all atherosclerotic lesions but in only 5% of control samples of arterial tissue.1 C pneumoniae lipopolysaccharides have been found in circulating immune complexes observed in chronically infected patients.16 These are known for their deleterious effects on the blood coagulation system and on vascular endothelium.31 32 33 Persistent C pneumoniae infection is associated with increased fibrinogen levels, indicating inflammation and a procoagulant state.18 Finally, 2 preliminary intervention studies have indicated that treatment with antibiotics might improve prognosis for patients with coronary heart disease.34 35
In contrast to C pneumoniae, high titers to CMV were not associated with any increase in morbidity or mortality. On the contrary, the RR for cardiovascular death had a 95% CI of 0.02 to 0.93. This is an intriguing finding, considering that several previous studies have indicated an association between CMV seropositivity and atherosclerosis.1 However, as summarized in the cited overview, it should be kept in mind that more than 1200 of the 1600 reviewed cases were defined on the basis of coronary restenosis after atherectomy, or the development of lesions in transplanted hearts or in arteries outside the coronary circulation. Thus, as summarized in this review, even if CMV does cause such lesions, the infection may not be relevant to native overt cardiovascular disease. A recently published study in approximately 900 patients did not find any association between CMV seropositivity and angiographically demonstrated coronary artery atherosclerosis.36 Against this background, it should be emphasized that the present study is the first to have examined prospectively the relationship between CMV titers and hard end points, such as cardiovascular mortality.
The question of whether our observation that CMV seropositivity was associated with a lower risk for future cardiovascular death was a random finding or may be explained by selection bias cannot be solved until other prospective studies on clinical events have been performed. The study was based on conventional epidemiological methods to select patients from population-representative samples of hypertensive men, and the studied subgroup was randomly selected.10 11 12
The observation that 85% of the patients showed seropositivity to CMV is in accordance with the expected prevalence.5 From a principal viewpoint, it is difficult to elucidate the impact of a risk factor that is found in all or almost all patients.
The conclusions which can be derived from this study are that the methods used to analyze and define chronic C pneumoniae infection seemed to be valid, and that seropositivity according to this approach was associated with an increased risk of future cardiovascular disease, stroke in particular. Larger studies are urgently needed to clarify whether a chronic C pneumoniae infection is a risk factor for stroke.
|
Acknowledgments |
|---|
This study was supported by grants from the Swedish Medical Research Council (B92-19X-09937-01A, B93-19X-09937-02B, B94-19X 09937-02B, and B95-19X-09937-04B), the Swedish Heart and Lung Foundation, the Swedish Hypertension Society and King Gustaf V and Queen Viktoria Foundation, and Astra Hässle AB, Mölndal, Sweden. We are grateful for the support provided by Gunnar Olsson, Director, Astra Hässle AB. We thank Eva-Lena Alenhag, Caroline Schmidt, and Jessica Nääs for their excellent technical assistance and Anders Odén, PhD, for performing the statistical analyses.
Received September 10, 1998; revision received November 3, 1998; accepted November 10, 1998.
|
References |
|---|
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
1. Danesh J, Collins R, Peto R. Chronic infections and coronary heart disease: is there a link? Lancet. 1997;350:430–436.[Medline] [Order article via Infotrieve]
2. Grayston, JT. Infections caused by Chlamydia pneumoniae strain TWAR. Clin Infect Dis. 1992;15:757–763.[Medline] [Order article via Infotrieve]
3. Gnarpe, H., Gnarpe, J. Increasing prevalence of specific antibodies to Chlamydia pneumoniae in Sweden. Lancet. 1993;341:381.
4. Saikku P, Leinonen M, Tenkanen L, Linnanmäki E, Ekman M-R, Manninen V, Mänttäri M, Frick MH, Huttunen JK. Chronic Chlamydia pneumoniae infection as a risk factor for coronary heart disease in the Helsinki heart study. Ann Intern Med. 1992;116:273–278.
5. Bruggeman CA. Cytomegalovirus and latency: an overview. Virchows Arch B Cell Pathol Incl Mol Pathol. 1993;64:325–333.[Medline] [Order article via Infotrieve]
6. Melnick SL, Shahar E, Folsom AR, Grayston JT, Sorlie PD, Wang S-P, Szklo M. Past infection by Chlamydia pneumoniae strain TWAR and asymptomatic carotid atherosclerosis. Am J Med. 1993;95:499–504.[Medline] [Order article via Infotrieve]
7. Cook PJ, Lip GYH, Zarifis J, Sagar G, Honeybourne, Wise R, Beevers DG. Elevated Chlamydia pneumoniae antibody titers are associated with acute stroke syndromes. Circulation. 1995;92(suppl I):I-482–I-483. Abstract.
8.
Wimmer MLJ, Sandmann-Strupp R, Saikku P, Haberl RL.
Association of Chlamydia pneumoniae with cerebrovascular
disease. Stroke. 1996;27:2207–2210.
9.
Nieto FJ, Adam E, Sorlie P, Farzadegan H, Melnick JL,
Comstock GW, Szklo M. Cohort study of cytomegalovirus infection as a
risk factor for carotid intimal-media thickening, a measure of
subclinical atherosclerosis. Circulation. 1996;94:922–927.
10. Agewall S, Fagerberg B, Berglund G, Andersson OK, Hedner T, Persson B, Samuelsson O, Wikstrand J. Multiple cardiovascular risk factor intervention: what could be achieved? Nutr Metab Cardiovasc Dis.. 1993;3:128–35.
11. Fagerberg B, Wikstrand J, Berglund G, Samuelsson O, Agewall S, for the Risk Factor Intervention Study Group. Mortality rates in treated hypertensive men with additional risk factors are high but can be reduced: a randomized intervention study. Am J Hypertens. 1998;11:14–22.[Medline] [Order article via Infotrieve]
12.
Suurküla M, Agewall S, Fagerberg B,
Wendelhag I, Widgren B, Wikstrand J. Ultrasound evaluation of
atherosclerotic manifestations in the carotid artery in high risk
hypertensive patients. Arterioscler Thromb. 1994;14:1297–1304.
13.
Suurküla M, Agewall S, Fagerberg B, Wendelhag I,
Wikstrand J. Multiple risk intervention in high-risk hypertensive
patients: a 3-year ultrasound study of intima-media thickness and
plaques in the carotid artery. Arterioscler Thromb Vasc
Biol. 1996;16:462–470.
14.
Jauhianinen T, Toumi T, Leinonen M, Kark JD, Saikku P.
Interference of immunoglobulin G (IgG) antibodies in IgA antibody
determinations for Chlamydia pneumoniae by
microimmunofluorescence test. J Clin
Microbiol. 1994;32:839–840.
15.
Gabriel AS, Gnarpe H, Gnarpe J, Hallander H, Nyquist O,
Martinsson A. The prevalence of chronic Chlamydia pneumoniae
infection as detected by polymerase chain reaction in pharyngeal
samples from patients with ischemic heart disease. Eur
Heart J. 1998;19:1321–1327.
16.
Linnanmäki E, Leinonen M, Mattila K, Nieminen MS,
Valtonen V, Saikku P. Chlamydia pneumoniae-specific
circulating immune complexes in patients with chronic coronary
heart disease. Circulation. 1993;87:1130–1134.
17. Breslow NE, Day NE. Statistical methods in cancer research, vol II: the design and analysis of cohort studies. IARC Sci Publ.. 1987;82:131–135.
18.
Toss H, Gnarpe J, Gnarpe H, Siegbahn A, Lindahl B,
Wallentin L. Increased fibrinogen levels are associated with persistent
Chlamydia pneumoniae infection in unstable coronary
artery disease. Eur Heart J. 1998;19:570–577.
19. Falck G, Heyman L, Gnarpe J, Gnarpe H. Chlamydia pneumoniae and chronic pharyngitis. Scand J Infect Dis. 1995;27:179–182.[Medline] [Order article via Infotrieve]
20. Falck G, Gnarpe J, Gnarpe H. Persistent Chlamydia pneumoniae infection in a Swedish Family. Scand J Infect Dis. 1996;28:271–273.[Medline] [Order article via Infotrieve]
21. Falck G, Engstrand I, Gad A, Gnarpe J, Gnarpe H, Laurila A. Demonstration of Chlamydia pneumoniae in patients with chronic pharyngitis. Scand J Infect Dis. 1997;29:585–589.[Medline] [Order article via Infotrieve]
22.
Hahn DL, Golubjatnikov R. Smoking is a potential
confounder of the Chlamydia pneumoniae: coronary
artery disease association. Arterioscler Thromb. 1992;12:945–947.
23.
Karvonen M, Tuomilehto J, Pitkäniemi J,
Naukkarinen A, Saikku P. Importance of smoking for Chlamydia
pneumoniae seropositivity. Int J Epidemiol. 1994;23:1315–1321.
24.
Miettinen H, Lehto S, Saikku P, Haffner SM,
Rönnemaa T, Pyörälä K, Laakso M. Association of
Chlamydia pneumoniae and acute coronary heart
disease events in non-insulin dependent diabetic and non-diabetic
subjects in Finland. Eur Heart J. 1996;17:682–688.
25.
Cook PJ, Lip GYH, Davies P, Beevers DG, Wise R,
Honeybourne D. Chlamydia pneumoniae antibodies in severe
essential hypertension. Hypertension. 1998;31:589–594.
26.
Patel P, Mendall MA, Carrington D, Strachan DP, Leatham
E, Molineaux N, Levy J, Blakeston C, Seymour CA, Camm AJ, Northfield
TC. Association of Helicobacter pylori and Chlamydia
pneumoniae infections with coronary heart disease and
cardiovascular risk factors. BMJ. 1995;311:711–714.
27.
Laurila A, Bloigu A, Näyhä S, Hassi J,
Leinonen M, Saikku P. Chlamydia pneumoniae antibodies and
serum lipids in Finnish men: cross sectional study. BMJ. 1997;314:1456–1457.
28. Ossewaarde JM, Vallinga C, Feskens EJM, Kromhout D. Infection with Chlamydia pneumoniae as a risk factor for coronary heart disease (the Zutphen Elderly Study). Atherosclerosis.. 1005;115:S13. Abstract 41.
29. Fong IW, Chui B, Viira E, Fong MW, Jang D, Mahoney J. Rabbit model for Chlamydia pneumoniae infection. J Clin Microbiol. 1997;35:48–52.[Abstract]
30. Laitinen K, Laurila A, Pyhälä L, Leinonen M, Saikku P. Infection induces inflammatory changes in the aortas of rabbits. Infect Immun. 1997;65:4382–4385.
31. Morrison DC, Cline LF. Activation of the classical and properdin pathways of complement by bacterial lipopolysaccharides (LPS). J Immunol. 1977;118:326–329.
32. Harlan JM, Harker LA, Stricker GE, Deaver LJ. Effects of lipopolysaccharide on human endothelial cells in culture. Thromb Res. 1983;29:15–26.[Medline] [Order article via Infotrieve]
33. Libby P, Ordovas JM, Aauger KR, Robbins AH, Birinyi KK, Dinarello CA. Endotoxin and tumor necrosis factor induced interleukin-1 gene expression in adult human vascular endothelial cells. Am J Pathol. 1986;124:179–185.[Abstract]
34.
Gupta S, Leatham EW, Carrington D, Mendall MA, Kaski
JC, Camm AJ. Elevated antibodies, cardiovascular
events, and azithromycin in male survivors of myocardial infarction.
Circulation. 1997;96:404–407.
35. Gurfinkel E, Bozovich G, Daroca A, Beck E, Mautner B. Randomised trial of roxithromycin in non-Q-wave coronary syndromes: ROXIS Pilot Study. Lancet. 1997;350:404–407.[Medline] [Order article via Infotrieve]
36. Adler SP, Hur JK, Wang JB, Vetrovec GW. Prior infection with cytomegalovirus is not a major risk factor for angiographically demonstrated coronary artery atherosclerosis. J Infect Dis. 1998;177:209–212.[Medline] [Order article via Infotrieve]
This article has been cited by other articles:
 |
|
 |
|
  L. B. Goldstein, R. Adams, M. J. Alberts, L. J. Appel, L. M. Brass, C. D. Bushnell, A. Culebras, T. J. DeGraba, P. B. Gorelick, J. R. Guyton, et al. Primary Prevention of Ischemic Stroke: A Guideline From the American Heart Association/American Stroke Association Stroke Council: Cosponsored by the Atherosclerotic Peripheral Vascular Disease Interdisciplinary Working Group; Cardiovascular Nursing Council; Clinical Cardiology Council; Nutrition, Physical Activity, and Metabolism Council; and the Quality of Care and Outcomes Research Interdisciplinary Working Group: The American Academy of Neurology affirms the value of this guideline. Circulation, June 20, 2006; 113(24): e873 - e923. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. B. Goldstein, R. Adams, M. J. Alberts, L. J. Appel, L. M. Brass, C. D. Bushnell, A. Culebras, T. J. DeGraba, P. B. Gorelick, J. R. Guyton, et al. Primary Prevention of Ischemic Stroke: A Guideline From the American Heart Association/American Stroke Association Stroke Council: Cosponsored by the Atherosclerotic Peripheral Vascular Disease Interdisciplinary Working Group; Cardiovascular Nursing Council; Clinical Cardiology Council; Nutrition, Physical Activity, and Metabolism Council; and the Quality of Care and Outcomes Research Interdisciplinary Working Group: The American Academy of Neurology affirms the value of this guideline. Stroke, June 1, 2006; 37(6): 1583 - 1633. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Guven, A. Cetinkaya, M. Aral, G. Sokmen, M. A. Buyukbese, A. Guven, and N. Koksal High-Sensitivity C-Reactive Protein in Patients with Metabolic Syndrome Angiology, May 1, 2006; 57(3): 295 - 302. [Abstract] [PDF]
|
|
|
|
|
|
M. S.V. Elkind, M. L. C. Tondella, D. R. Feikin, B. S. Fields, S. Homma, and M. R. Di Tullio Seropositivity to Chlamydia pneumoniae Is Associated With Risk of First Ischemic Stroke Stroke, March 1, 2006; 37(3): 790 - 795. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. K. Njamnshi, K. N. Blackett, J. N. Mbuagbaw, F. Gumedze, S. Gupta, and C. S. Wiysonge Chronic Chlamydia pneumoniae Infection and Stroke in Cameroon: A Case-Control Study Stroke, March 1, 2006; 37(3): 796 - 799. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. J. Lindsberg and A. J. Grau Inflammation and Infections as Risk Factors for Ischemic Stroke Stroke, October 1, 2003; 34(10): 2518 - 2532. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T-M Lin, W-j Chen, H-Y Chen, P-W Wang, and H-L Eng Increased incidence of cytomegalovirus but not Chlamydia pneumoniae in atherosclerotic lesions of arteries of lower extremities from patients with diabetes mellitus undergoing amputation J. Clin. Pathol., June 1, 2003; 56(6): 429 - 432. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. D. Curb, R. D. Abbott, B. L. Rodriguez, P. Sakkinen, J. S. Popper, K. Yano, and R. P. Tracy C-Reactive Protein and the Future Risk of Thromboembolic Stroke in Healthy Men Circulation, April 22, 2003; 107(15): 2016 - 2020. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Smieja, J. Gnarpe, E. Lonn, H. Gnarpe, G. Olsson, Q. Yi, V. Dzavik, M. McQueen, S. Yusuf, and for the Heart Outcomes Prevention Evaluation (HOPE Multiple Infections and Subsequent Cardiovascular Events in the Heart Outcomes Prevention Evaluation (HOPE) Study Circulation, January 21, 2003; 107(2): 251 - 257. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Veres, G. Fust, M. Smieja, M. McQueen, A. Horvath, Q. Yi, A. Biro, J. Pogue, L. Romics, I. Karadi, et al. Relationship of Anti-60 kDa Heat Shock Protein and Anti-Cholesterol Antibodies to Cardiovascular Events Circulation, November 26, 2002; 106(22): 2775 - 2780. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Falck, J. Gnarpe, L.-O. Hansson, K. Svardsudd, and H. Gnarpe Comparison of Individuals With and Without Specific IgA Antibodies to Chlamydia pneumoniae: Respiratory Morbidity and the Metabolic Syndrome Chest, November 1, 2002; 122(5): 1587 - 1593. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J.A. Erkens, O.H. Klungel, R.M.C. Herings, R.P. Stolk, J.A. Spoelstra, D.E. Grobbee, and H.G.M. Leufkens Use of fluorquinolones is associated with a reduced risk of coronary heart disease in diabetes mellitus type 2 patients Eur. Heart J., October 2, 2002; 23(20): 1575 - 1579. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Vainas, H. A.J.M. Kurvers, W. H. Mess, R. d. Graaf, R. Ezzahiri, J. H.M. Tordoir, G.-W. H. Schurink, C. A. Bruggeman, and P. J.E.H.M. Kitslaar Chlamydia pneumoniae Serology Is Associated With Thrombosis-Related but Not With Plaque-Related Microembolization During Carotid Endarterectomy Stroke, May 1, 2002; 33(5): 1249 - 1254. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Stollberger and J. Finsterer Role of Infectious and Immune Factors in Coronary and Cerebrovascular Arteriosclerosis Clin. Vaccine Immunol., March 1, 2002; 9(2): 207 - 215. [Full Text] [PDF]
|
|
|
|
|
|
P. B. Gorelick Stroke Prevention Therapy Beyond Antithrombotics: Unifying Mechanisms in Ischemic Stroke Pathogenesis and Implications for Therapy: An Invited Review Stroke, March 1, 2002; 33(3): 862 - 875. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. S. Elkind, J. Cheng, B. Boden-Albala, T. Rundek, J. Thomas, H. Chen, L. E. Rabbani, R. L. Sacco, and A. G. Thrift Tumor Necrosis Factor Receptor Levels Are Associated With Carotid Atherosclerosis * Editorial Comment Stroke, January 1, 2002; 33(1): 31 - 38. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. U. Heuschmann, D. Neureiter, M. Gesslein, B. Craiovan, M. Maass, G. Faller, G. Beck, B. Neundoerfer, and P. L. Kolominsky-Rabas Association Between Infection With Helicobacter pylori and Chlamydia pneumoniae and Risk of Ischemic Stroke Subtypes: Results From a Population-Based Case-Control Study Stroke, October 1, 2001; 32(10): 2253 - 2258. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Virok, Z. Kis, L. Karai, L. Intzedy, K. Burian, A. Szabo, B. Ivanyi, E. Gonczol, and M. S. Elkind Chlamydia pneumoniae in Atherosclerotic Middle Cerebral Artery Editorial Comment Stroke, September 1, 2001; 32(9): 1973 - 1976. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. S. Elkind, J. Cheng, B. Boden-Albala, M. C. Paik, and R. L. Sacco Elevated White Blood Cell Count and Carotid Plaque Thickness : The Northern Manhattan Stroke Study Stroke, April 1, 2001; 32(4): 842 - 849. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Sander, K. Winbeck, J. Klingelhofer, T. Etgen, and B. Conrad Enhanced Progression of Early Carotid Atherosclerosis Is Related to Chlamydia pneumoniae (Taiwan Acute Respiratory) Seropositivity Circulation, March 13, 2001; 103(10): 1390 - 1395. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Truelsen, E. Prescott, P. Lange, P. Schnohr, and G. Boysen Lung function and risk of fatal and non-fatal stroke. The Copenhagen City Heart Study Int. J. Epidemiol., February 1, 2001; 30(1): 145 - 151. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. B. Goldstein, R. Adams, K. Becker, C. D. Furberg, P. B. Gorelick, G. Hademenos, M. Hill, G. Howard, V. J. Howard, B. Jacobs, et al. Primary Prevention of Ischemic Stroke : A Statement for Healthcare Professionals From the Stroke Council of the American Heart Association Circulation, January 2, 2001; 103(1): 163 - 182. [Full Text] [PDF]
|
|
|
|
|
|
L. B. Goldstein, R. Adams, K. Becker, C. D. Furberg, P. B. Gorelick, G. Hademenos, M. Hill, G. Howard, V. J. Howard, B. Jacobs, et al. Primary Prevention of Ischemic Stroke : A Statement for Healthcare Professionals From the Stroke Council of the American Heart Association Stroke, January 1, 2001; 32(1): 280 - 299. [Full Text] [PDF]
|
|
|
|
|
|
S A Morre, W Stooker, W K Lagrand, A J C van den Brule, and H W M Niessen Microorganisms in the aetiology of atherosclerosis J. Clin. Pathol., September 1, 2000; 53(9): 647 - 654. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. W. Fong Emerging relations between infectious diseases and coronary artery disease and atherosclerosis Can. Med. Assoc. J., July 1, 2000; 163(1): 49 - 56. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. S. V. Elkind, I-F. Lin, J. T. Grayston, and R. L. Sacco Chlamydia pneumoniae and the Risk of First Ischemic Stroke : The Northern Manhattan Stroke Study Stroke, July 1, 2000; 31(7): 1521 - 1525. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 F. J. Kirkham, M. Prengler, D. K.M. Hewes, and V. Ganesan Risk Factors for Arterial Ischemic Stroke in Children J Child Neurol, May 1, 2000; 15(5): 299 - 307. [Abstract] [PDF]
|
|
|
|
 |
|
 T. Quaschning and C. Wanner The role of Chlamydia in coronary heart disease--fact or fiction? Nephrol. Dial. Transplant., December 1, 1999; 14(12): 2800 - 2803. [Full Text] [PDF]
|
|
|
|
|
|
C. A. Glader, B. Stegmayr, J. Boman, H. Stenlund, L. Weinehall, G. Hallmans, and G. H. Dahlen Chlamydia pneumoniae Antibodies and High Lipoprotein(a) Levels Do Not Predict Ischemic Cerebral Infarctions : Results From a Nested Case-Control Study in Northern Sweden Stroke, October 1, 1999; 30(10): 2013 - 2018. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||