(Circulation. 2004;109:1095-1100.)
© 2004 American Heart Association, Inc.
Clinical Investigation and Reports |
From Boston University Goldman School of Dental Medicine (S.-J.J., J.A.J.), Boston, Mass; Department of Otorhinolaryngology/Oral Surgery (M.Q.) and Department of Cardiothoracic Surgery (P.N.), Kuopio University Hospital, Kuopio, Finland; Institute of Dentistry (J.H.M.), University of Helsinki, Department of Oral and Maxillofacial Diseases, Helsinki University Central Hospital, Helsinki, Finland; National Institute of Neurological Disorders and Stroke (A.E.B.), National Institutes of Health, Bethesda, Md; Harvard School of Public Health (S.-J.J.), Harvard University, Boston, Mass; and VA Center for Health Quality, Outcomes and Economic Research (J.A.J.), Bedford, Mass.
Correspondence to Sok-Ja Janket, DMD, MPH, Department of General Dentistry, Boston University Goldman School of Dental Medicine, 100 E. Newton St, Boston, MA 02118. E-mail sjanket{at}hsph.harvard.edu
Received August 12, 2003; revision received October 31, 2003; accepted November 13, 2003.
| Abstract |
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Methods and Results A total of 256 consecutive Finnish cardiac patients from Kuopio University Hospital with angiographically confirmed CHD and 250 age-, gender-, and residence-matched noncardiac patients (controls) were recruited. All dental factors expected to generate inflammatory mediators, including pericoronitis, dental caries, dentate status, root remnants, and gingivitis, were examined, and an asymptotic dental score (ADS) was developed by logistic regression analyses with an appropriate weighting scheme according to the likelihood ratio. We validated the explanatory ability of ADS by comparing it to that of the Total Dental Index and examining whether the ADS was associated with known predictors of CHD. A model that included ADS, C-reactive protein, HDL, and fibrinogen offered an explanatory ability that equaled or exceeded that of the Framingham heart score (C statistic=0.82 versus 0.80). When ADS was removed from this model, the C-statistic decreased to 0.77, which indicates that the ADS was a significant contributor to the explanatory ability of a logistic model.
Conclusions ADS may be useful as a prescreening tool to promote proactive cardiac evaluation among individuals without overt symptoms of CHD. However, additional prospective study is needed to validate the use of an oral health score as a predictor of incident CHD.
Key Words: oral health heart diseases lipoproteins interleukins fibrinogen
| Introduction |
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See p 1076
| Methods |
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Participants
We recruited 256 consecutive cardiac patients with CHD confirmed by coronary angiography at Kuopio University Hospital. Potential subjects were excluded if they took antibiotics during the previous 30 days or had chronic infection other than dental disease. Also recruited were 250 age- and gender-matched patients from the same catchment area without any evidence of CHD who were admitted to general surgery or otorhinolaryngology at the same hospital. The same exclusion and inclusion criteria were applied to noncardiac patients. Additional exclusion criteria were (1) those who needed emergency coronary bypass surgery or valvular replacement surgery, (2) those whose disease status was so grave a dental examination or dental x-ray could not be taken safely, and (3) those who needed antibiotic prophylaxis before dental probing and examination.
Predictor Assessment
Panoramic tomograms of the jaws were taken, and signs of dental infection such as periapical radiolucencies, signs of long-standing dental decay or infection manifested either by pericoronitis (defined as an infection/inflammation surrounding the third molars [radiolucent follicle around the retained or erupting third molars with diameter
3 mm]) or numbers of root remnants with soft tissue inflammation (dental hard tissues are usually destroyed by advanced dental caries, leaving only tips of the root), amount of vertical bone loss (measured from cemento-enamel junction in millimeters), calculus deposits, and restorations with overhangs were recorded. A single examiner (MQ) performed all radiographic examinations twice, and agreement of the 2 readings was excellent (
=0.9).
The same examiner (MQ) performed clinical dental examinations immediately after panoramic radiography using the World Health Organization format.12 Dental caries was categorized from 1 to 4 in similar fashion as that suggested by Mattila et al,9 ie, 1=no caries, 2=1 to 3 caries surfaces, 3=4 to 7 carious surfaces or unimaxillary edentulism, and 4=more than 8 carious surfaces or bimaxillary edentulism. Gingivitis was recorded as yes or no. If gingival tissue exhibited overt signs of inflammation, namely, erythema, bleeding, and papillary or generalized swelling, then gingivitis was considered to be present.
Periapical lesions, which signify advanced dental caries or periodontal abscess, were categorized in 3 levels: none, 1, and 2 or more. Pericoronitis was recorded as present or absent by clinical examination and radiographic evaluation. Remaining root remnants were categorized in 3 levels: none, 1, and 2 or more. Periodontal disease was measured with the community periodontal index of treatment need (CPITN), and if at least 2 sextants (segments dividing mandible and maxilla into 6) were recorded as having CPITN
3 (signifying that sextant had periodontal pocket depth
3.5 mm), the patient was coded as having periodontal disease.
Medical and Clinical Laboratory Examinations
A team of cardiologists and cardiac surgeons examined CHD patients according to the Kuopio hospital protocol. A number of blood tests were performed to evaluate serum CRP levels, white blood cell counts, blood fibrinogen level, triglycerides, total cholesterol, HDL, and LDL cholesterol. All blood samples were analyzed immediately. The analyses were performed in batches that included both cases and controls to distribute any potential environmental changes and measurement errors evenly. The erythrocyte sedimentation rate was measured by Westergrens method in glass capillary tubes, and leukocyte count was measured by Coulter counter. Fibrinogen was measured by the Clauss method. A high-sensitivity immunoturbidometry assay was used to measure CRP with a HITACHI 717 analyzer.
Statistical Analyses
Using the Statistical Analysis System version 8.2, we evaluated all dental variables postulated to generate inflammatory mediators in a univariate model with CHD (yes/no) as a dependent variable and each dental parameter as a predictor. Sequentially, we added significant variables in the model to evaluate the relationship of variables, examining whether confounding or collinear relationships were present between the variables. Among many variables tested, 5 variables were associated with CHD, including pericoronitis, number of root remnants, dental caries, bimaxillary edentulism, and gingivitis. According to the likelihood ratio, we weighted each variable so that relative importance would be reflected in the prediction score according to the method suggested by Spiegelhalter et al.13 The final model with appropriate weights might be written as ADS=15xpericoro- nitis+5xroot tips+3xedentulism+4xcaries+5xgingivitis, similar to our previous work and the Framingham Heart Score.11,14 Subsequently, we regressed CHD status on the prediction score and evaluated model fit, and the receiver operating characteristics curve, a global assessment of explanatory ability, was created by plotting sensitivity by (1-specificity), ie, correct identification of CHD versus false-positive identification. Then we proceeded to add other independent CHD risk factors such as CRP, HDL, leukocyte count, and fibrinogen concentration to the model to ascertain whether any of them were confounders or collinear with ADS or with other covariates.
Validation
The explanatory ability of the ADS was validated by performing logistic regressions with established inflammatory and metabolic markers of CHD as dependent variables and the ADS as a predictor. In addition, we compared the explanatory ability of the ADS to that of the TDI, formulated by Mattila et al.15 To observe clinically meaningful robust changes, we created an ordinal scale of ADS under the assumption that an increased score would be associated with an increased risk of CHD. To make a fair comparison, we also created a TDI scale with the same assumption. The dependent variables were inflammatory and metabolic markers known to be predictive of CHD, including erythrocyte sedimentation rate, fibrinogen, CRP, leukocyte counts, HDL, triglycerides, and the ratio of total cholesterol to HDL, which was known to be a better predictor of coronary events than any 1 of them alone.14 The validity of our models was further tested by bootstrapping with 1000 repetitions.
| Results |
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The final logistic regression model contained 5 variables; pericoronitis, retained root remnants, edentulism, dental caries, and gingivitis. The Hosmer-Lemeshow test for the final model yielded 0.89, which indicates a good model fit. The area under the receiver operating characteristics curve, equated as the C-statistic, was 0.70, which suggests that this ADS had a slightly lower explanatory ability than the multivariable Framingham Heart score, with C-statistics ranging from 0.73 to 0.82. The validation results in relation to other independent risk factors of CHD are presented in Table 2. The ADS correctly identified 100% of metabolic and hematologic markers of CHD contained in this data set. In contrast, the TDI scale correctly identified only 3 of 8 markers of CHD.
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As a univariate predictor, the C-statistic was 0.7 for ADS alone, 0.60 for fibrinogen, 0.60 for triglycerides, 0.63 for HDL, and 0.62 for the ratio of total to HDL cholesterol. In bivariate models with ADS as a main predictor, a model that included ADS and CRP had the best explanatory ability, with a C-statistic of 0.74, whereas C-statistics for other models ranged from 0.72 to 0.73.
When other hematologic or metabolic factors such as CRP, HDL, leukocyte count, and fibrinogen were added 1 by 1, ADS showed signs of confounding by CRP and HDL according to the rule of thumb that a change of more than 10% in parameter estimate can be considered a sign of confounding. This suggested that ADS might be confluent with CRP and HDL. However, ADS remained significant, which indicates ADS is an independent predictor above and beyond the common pathways shared with markers of inflammatory process or lipid metabolism. Leukocyte counts and fibrinogen levels were also confounders of ADS, and leukocyte counts and fibrinogen levels, as expected, were collinear. Because fibrinogen was a much stronger contributor to the explanatory ability, we retained fibrinogen and removed leukocyte counts from the model for the reason of parsimony. This final model consisting of ADS, CRP, HDL, and fibrinogen conferred an 82% explanatory ability, which equaled/exceeded that of the Framingham Heart Score.16 This result is presented in Figure 1. When ADS was removed from the best model, the explanatory ability was reduced from 82% to 77%, which suggests that ADS is a significant additional contributor to the explanatory ability of the model containing 3 factors, ie, inflammatory, lipid, and hemostatic factors (Table 3).
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In the bootstrapping procedure to test the robustness of our results, all the variables remained significant after 1000 repetitions with random selection of variances, which indicates that it is highly unlikely that our results were due to chance.
| Discussion |
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Some studies reported that periodontal disease might contribute to the generation of inflammatory mediators.5,17,18 In a meta-analysis of 5 cohort studies, an increased relative risk of CHD due to periodontal disease was reported, but dental disease was considered as a confounder for socioeconomic and behavioral risk factors for CHD, presumably because well-conducted epidemiological studies reported null results.19 A recent meta-analysis20 of 9 studies also yielded a modest but significant increase in relative risk similar to the result of the previous meta-analysis21 among individuals with periodontal disease compared with those without. However, the subgroup analyses performed in the latest meta-analysis indicated that there was a significant underestimation (29.7%) of relative risk in epidemiological studies that used self-reported periodontal status.20 This attenuation due to nondifferential misclassification was remarkably similar to the reported attenuation of 30% by Joshipura et al.22 In addition, when oral health status was measured by the number of teeth, which is a more precise assessment than a patients report of past history of periodontitis, a significant association between oral health and risk of stroke was observed in the same cohort.22
Although ADS was significantly associated with CHD, we cannot derive any causal inferences. Resolution of the issue of whether oral health status is a contributor or confounder of CHD may be answered by randomized trials. For ethical and financial reasons, a primary prevention trial assigning periodontal disease to examine the relation with future CHD is not feasible. In addition, secondary prevention does not confer an unbiased biological relationship, because individuals who have had prior CHD are at a higher risk.23 Some studies reported that the intake of some nutrients and foods protective against CHD, such as fruits, vegetables, and fibers, was lower in edentulous patients, and thus it is possible that oral health indirectly affected the risk of CHD via nutrition intake.2427 Other studies reported that carbohydrates with high glycemic index were associated with elevated CRP, which suggests that dietary factors may contribute to the inflammatory process.28 It has been reported that edentulous subjects tend to take in higher levels of carbohydrates,24 which may possibly increase the level of CRP. After reviewing all of this evidence, we offer an alternative hypothesis regarding socioeconomic factors and oral health in Figure 2.
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Unfortunately, some of the traditional CHD risk factors were not available in our data set. Nevertheless, our model with ADS, CRP, HDL, and fibrinogen was on a par with the prediction ability of the Framingham model. Because smoking, diabetes, and hypertension were often associated with abnormal fibrinogen,16 by substituting fibrinogen for them, our model achieved comparable explanatory capability with a more parsimonious model. The present results clearly reaffirm previous comments that "dental disease may be partly contributive and definitely predictive."29 However, further research is needed to validate the ADS in prospective cohort studies.
Study Limitations
Because our control subjects were selected from hospital patients, selection bias might be a potential problem. However, considering these controls were from the same catchment area where cases arose, it is unlikely that the effect of selection bias affected our results. Because the most severe cases of CHD were excluded, the present study may be a very conservative estimation of the explanatory ability of ADS.
As seen in Table 1, it appeared that the CHD group might have modified their lifestyles and that the cases and controls became quite similar in respect to other CHD risk factors such as smoking reduction and lowering their cholesterol levels. This might have helped us to detect a subtle contribution of oral health to the pathogenesis of CHD.30
Conclusions
The ADS, which asymptotically summed 5 oral pathologies that were expected to contribute to the generation of inflammatory mediators, was significantly associated with CHD. The ADS may be useful as a prescreening tool for subjects without overt cardiac symptoms to encourage them to seek early cardiac evaluation.
| Acknowledgments |
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