| Summary: | 碩士 === 國立成功大學 === 公共衛生研究所 === 93 === Abstract
Coronary heart disease (CHD) is one of the predominant causes of death and disability in all industrialized countries. Acute myocardial infarction (AMI), a major disease of CHD, is one of the leading causes of death in Taiwan. Among risk factors identified by epidemiological studies, smoking, hypertension, and diabetes mellitus are considered the most important predictors for the risk of AMI at the individual level.
It was hypothesized that atherosclerosis results from chronic inflammation. Recent studies have also indicated that chronic infection plays an important role in the process of atherosclerosis. A growing number of seroepidemiologic studies, in vitro tissue culture and animal studies conducted in Western countries have indicated that Chlamydia pneumoniae might be the major infectious cause of atherosclerogensis. However, there have been few epidemiologic studies on the link of C. pneumoniae infection and CHD in Taiwan, where the infection is highly prevalent.
A 1:2 individual-matched case-control study was conducted to investigate the association between C. pneumoniae infection and first-episode AMI and its effect measure modification on the association between traditional risk factors and AMI. Patients who were admitted to Chi-Mei Medical Center and were diagnosed with first-episode AMI during 2003 February 17 to 2004 February 16 were recruited. Individuals who had health examination at Chi-Mei Medical Center and were matched on sex and age of cases were selected as controls. Venous blood samples were collected and DNAs were extracted from peripheral blood mononuclear cells (PMBC) from all subjects. C. pneumoniae specific IgG antibody was measured by microimmunofluorescence test (IgG titers≧1：16 defined as seropositive or presence of past infection). In addition, presence of current C. pneumoniae infection was detected by polymerase chain reaction on extracted PBMC DNAs. Classical risk factors such as smoking, hypertension and diabetes mellitus were obtained from patients’ medical records and the questionnaires.
Overall, 74 first-episode AMI cases and 132 controls were recruited. Among cases, 82.4% were C. pneumoniae seropositive as compared to 68.9% of controls (p<0.05). The geometric mean C. pneumoniae IgG titer in cases was 14.9 compared to 11.3 in controls (p=0.31). No recent or current C. pneumoniae infections were found among all participants. C. pneumoniae IgG antibody seropositivity was not associated with first-episode AMI (OR=1.74, 95% CI=0.63-4.79, p=0.29) by multivariate logistic regression analysis. But the C. pneumoniae IgG titer was associated with first-episode AMI. When individuals with C. pneumoniae IgG titer ≧1：32, the odds ratio of having first-episode AMI was 8.92 as compared to those with titer ≦1：8 (95% CI=1.84-43.17, p<0.05). After controlling for other confounding factors, interactions were present between C. pneumoniae IgG antibody seropositivity and other classical risk factors such as- smoking (OR=4.04, 95% CI=1.17-14.00，p<0.05), diabetes mellitus (OR=5.67, 95% CI=1.55-20.74，p<0.05) and hypertension (OR=3.90, 95% CI=1.07-14.30，p<0.05) on the presence of first-episode AMI. Noticeably, when the individuals with all four risk factors were 12.3 times more likely to have first-episode AMI than those without（95% CI=1.29-118.21, p<0.05）.
Our data support the hypothesis that elevated C. pneumoniae IgG antibody titer is an independent risk factor for first-episode AMI in this southern Taiwan population. Results also suggest that presence of past C. pneumoniae infection is an important effect measure modifier on the association of the traditional risk factors and first-episode AMI. The prevention strategy on first-episode AMI and even on CHD should emphasize on an integrated prevention program involving C. pneumoniae infection and other classical risk factors should be warranted in the future.
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