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RESEARCH REPORT |
Department of Epidemiology, Mailman School of Public Health, Columbia University, 722 West 168th Street, 16th Floor, Room 1611, New York, NY 10032, USA;
Department of Epidemiology, and Department of Cariology, Restorative Sciences & Endodontics, University of Michigan School of Public Health, Ann Arbor, USA;
* corresponding author, lnb2{at}columbia.edu
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS & METHODSRESULTSDISCUSSIONREFERENCES |
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KEY WORDS: race/ethnicity • periodontitis • prevalence • national surveys
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS & METHODSRESULTSDISCUSSIONREFERENCES |
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MATERIALS & METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS & METHODSRESULTSDISCUSSIONREFERENCES |
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During the dental examination, dentists trained in the survey examination protocol conducted the periodontal examinations (National Center for Health Statistics, 1996; National Health and Nutrition Examination Survey, 2001a). Briefly, the periodontal examination was conducted at 2 sites, mid-buccal and mesiobuccal, for each tooth, in 2 randomly chosen quadrants, 1 maxillary and 1 mandibular, on the assumption that conditions in these 2 quadrants would represent the mouth. Third molars were excluded because of their frequent extraction in young adulthood, so a maximum 14 teeth and 28 sites per individual were examined. Previous studies used several combinations of clinical attachment loss (CAL) and pocket depth (PD) to establish periodontitis case-definitions (Beck et al., 1990; Machtei et al., 1992; Locker and Leake, 1993). For this study, the distribution of CAL and PD was evaluated in the total population as well as in each racial/ethnic group in each survey. Prior to any hypothesis testing, we tested several case-definitions before arriving at the one used in this analysis. A periodontitis case was defined as a person who had at least 3 sites with CAL 
4 mm and at least 2 sites with PD 3 mm. However, these conditions did not have to be present in the same site or tooth.
The main independent variable of interest was race/ethnicity, defined in both surveys as non-Hispanic black, non-Hispanic white, and Mexican-American. For this paper, non-Hispanic black and non-Hispanic white will be referred to as black and white, respectively.
For estimation of the association between race/ethnicity and periodontitis adjusted for other factors, the following variables were included in the analysis: age at interview, gender, marital status, place of birth, education, income, presence of health insurance, history of diabetes, and tobacco use. The NHANES III and the NHANES 1999–2000 used the same or similar questions to record these covariates. Age, gender, and presence of health insurance were included in the analyses as collected in both surveys. Among participants with health insurance, a follow-up question (yes/no) was asked regarding dental coverage. Categories in the marital status question originally included married, living together with someone as married, widowed, divorced, separated, or never married. These categories were grouped into married (married or living together with someone as married), single, divorced (separated or divorced), and widowed. Place of birth was recorded as having been born in the USA or elsewhere. Education was recorded as a continuous variable, from 0 to 17 yrs of education in the NHANES III and as < 12 yrs, 12 yrs, and > 12 yrs of education in the NHANES 1999–2000. The latter categories were used in both surveys. Total family 12-month income during the preceding year was also recorded as a continuous variable and was recoded after incomes reported in the NHANES 1999–2000 were adjusted to the equivalent dollar amount in the NHANES III (US Department of Labor, 2004). Income was categorized as low, medium, or high. These categories were: 
$14,999, $15,000 to $24,999, and $25,000 in the NHANES III; and $19,999, $20,000 to $34,999, and $35,000 in the NHANES 1999–2000, respectively. Time since last dental visit was categorized in both surveys as follows: 1 yr; > 1 but 2 yrs; > 2 but 5 yrs; and > 5 yrs.
The question "Have you ever been told by a doctor that you have diabetes?" was used to assess the history of diagnosed diabetes in both surveys. Diabetes that manifested in women only during pregnancy was excluded. Smoking status was derived from 2 questions in both surveys, "Do you smoke cigarettes now?" and "Have you smoked at least 100 cigarettes in your entire life?" Smoking status was defined as current smokers (subjects who answered "Yes" to both questions), former smokers (subjects who answered "No" to the first question and "Yes" to the second question), and never-smokers (subjects who answered "No" to both questions).
Statistical Analysis
Descriptive statistics for the characteristics of the population and the prevalence of periodontitis were calculated by race/ethnicity in each survey. Chi-square (discrete variables) and t tests (continuous variables) were used for the determination of significant differences. Cochran-Mantel-Haenszel chi-square tests were used for assessment of the independence of the prevalence of periodontitis by race/ethnicity, stratified by each covariate in each survey.
We used logistic regression to estimate the strength of the association between race/ethnicity and the prevalence of periodontitis in each survey. Specifically, we performed 5 sets of analyses to estimate: (1) crude odds ratios (OR); (2) ORs adjusted for age, gender, and place of birth (AOR 1); (3) ORs additionally adjusted for smoking and diabetes (AOR 2); (4) ORs additionally adjusted for health insurance and time since last dental visit (AOR 3); and (5) ORs additionally adjusted for education and income (AOR 4). Interaction terms between race/ethnicity and gender, income, and education were tested in each survey.
Data management procedures were carried out with SAS (SAS Institute Inc., 2004). Statistical analyses were conducted with SUDAAN (Research Triangle Institute, 2004) to take into account the complex sampling design yielding unbiased standard error estimates. In the Tables, the sample sizes were unweighted. However, estimates for means, proportions, standard errors, and ORs with their 95% confidence intervals (CI) were weighted.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS & METHODSRESULTSDISCUSSIONREFERENCES |
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). However, the proportion of people without health insurance and the prevalence of diabetes increased between surveys for all racial/ethnic groups.
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). In general, this pattern was consistent across all covariates. Although foreign-born Mexican-Americans in the NHANES III exhibited prevalence similar to that of their US-born counterparts (7.3% vs. 6.5%, p = 0.27), US-born Mexican-Americans exhibited lower prevalence than their foreign-born counterparts in the NHANES 1999–2000 (2.5% vs. 6.1%, p = 0.03).
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). There was no statistically significant difference in the odds of having periodontitis for Mexican-Americans vs. whites in either survey. After adjustment for all covariates, blacks were 1.88 times (95%CI: 1.42, 2.50) more likely to have periodontitis than were whites in the NHANES III. However, the fully adjusted odds of having periodontitis for blacks and Mexican-Americans was not statistically different from the odds for whites in the NHANES 1999–2000. These findings are consistent with the adjusted prevalence for periodontitis for each racial/ethnic group in each survey. For the NHANES III, the adjusted prevalences for whites, blacks, and Mexican-Americans were 6.2%, 10.1%, and 6.0%, respectively; while for the NHANES 1999–2000, the corresponding prevalences were 4.0%, 5.1%, and 2.9%, respectively. We repeated the analyses for the final model (AOR 4), including number of teeth present at examination, and the odds for blacks having periodontitis changed to 1.63 (95% CI: 1.23, 2.16) in the NHANES III but remained nearly identical in the NHANES 1999–2000 (1.31 [95% CI: 0.60, 2.87]). The results for Mexican-Americans remained unchanged (data not shown). These associations did not differ by sex or income in either survey. However, blacks and Mexican-Americans with less than a high school diploma were 3.19 and 3.39 times, respectively, more likely to have periodontitis than were highly educated whites in the NHANES 1999–2000, but not in the NHANES III (p-interaction = 0.04, data not shown).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS & METHODSRESULTSDISCUSSIONREFERENCES |
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Results from previous studies investigating trends in the prevalence of periodontal diseases in the USA have been mixed. For example, Douglass et al.(1983), comparing data from the Health Examination Survey (HES, 1960–62) and the NHANES I (1971–74), found that the Periodontal Index mean values remained nearly unchanged between the HES (1.13) and the NHANES I (1.09). However, the proportion of adults with periodontal pockets decreased between surveys (from 30.1% to 26.6%). Although the NHANES I and the then-National Institute of Dental Research (NIDR) National Survey of Oral Health in US Employed Adults and Seniors (1985–86) used a different periodontal examination protocol, Capilouto and Douglass (1988) found a decrease in periodontal diseases between the NHANES I and the NIDR adult survey, as measured by disease with pockets in the NHANES I (23.4%) and the presence of PD 4 mm in the NIDR survey (18.2%). However, the authors underscored the influence of the use of a partial-mouth examination (2 sites in 2 randomly chosen quadrants) and a sample of employed adults on the NIDR adult survey results. Finally, Hugoson et al.(1998), using data from 3 Swedish surveys of the adult population over 20 yrs old, found an increase in the number of healthy individuals and a decrease in the number of individuals with moderate periodontal bone loss between 1973 and 1983, but no change between 1983 and 1993. The authors suggest that the socio-economic climate and the lack of importance placed on oral hygiene by the younger population could have contributed to the observed plateau in periodontal disease. Our study found a lower prevalence of periodontitis for all racial/ethnic groups in the NHANES 1999–2000 relative to the NHANES III. Additionally, for the NHANES 1999–2000, the fully adjusted model indicated that there is no longer a significant difference in the odds of having periodontitis among racial/ethnic groups. Because these 2 surveys used the same periodontal examination protocol, the possibility of bias or artifact affecting the observed change is greatly reduced. In addition, if bias had occurred, it would have been non-differential in both surveys, thus, neither systematically under- nor over-estimating our results from either survey. Finally, we repeated the analyses using stringent case-definitions, and the results remained nearly identical to those presented here. Therefore, it is very unlikely that our results would be different if a different definition were used.
Our study shows a lower prevalence of periodontitis for all racial/ethnic groups in the NHANES 1999–2000 relative to the NHANES III. Possible explanations for the observed difference in periodontitis between surveys could be attributed to awareness and changes in health risk behaviors such as smoking. The prevalence of current smokers decreased between the 2 surveys for all racial/ethnic groups. Although the NHANES 1999–2000 sample size is small relative to the NHANES III, and issues related to sampling variation could be raised, estimates for diabetes and smoking status obtained from the NHANES 1999–2000 for each racial/ethnic group were comparable with estimates obtained from the National Health Interview Survey 1999 and 2000, an annual survey of approximately 31,000 adults aged 18 yrs and older (1999 National Health Interview Survey, 2002; 2000 National Health Interview Survey, 2002). Similarly, the education and income estimated by the US Census Bureau indicated a significant change in educational attainment and median income for blacks between 1994 and 1999 (Educational attainment, 2005; Historical Income Tables, 2005). Thus, despite the NHANES 1999–2000 sample size, the estimates obtained from the NHANES 1999–2000 are representative of the US population. Therefore, the observed difference in the prevalence of periodontitis between surveys could be an early sign of a downward trend in periodontitis among US adults.
Our analyses showed that the effect of race/ethnicity on periodontitis was modified by education in the NHANES 1999–2000 only after adjustment for all covariates in the model: Less-educated blacks and Mexican-Americans exhibited higher odds of having periodontitis than did highly educated whites. This finding underscored the disease burden of disadvantaged groups in our society.
Among the strengths of this study are: the use of 2 surveys with representative national samples; the use of the same case-definition for periodontitis in both surveys, allowing for a direct comparison; and the large sample size, which allows us to control for numerous potential confounders and examine interactions. Important limitations are the cross-sectional nature of the data, which precludes the drawing of inferences regarding cause and effect, and the small sample size for the NHANES 1999–2000 relative to the NHANES III. However, because the 95%CIs observed for the estimates for the NHANES 1999–2000 were reasonably narrow, we doubt that sample size, after weighting, represented a threat to our results. Future research, including additional years of the ongoing NHANES data collection, will help address this issue further. Finally, a limitation inherent to the collection of periodontal data via national surveys is the use of partial-mouth recording, with only 2 sites (mid-buccal and mesiobuccal) in 2 randomly selected quadrants examined, under the assumption that these measurements are representative of the full mouth (Albandar et al., 1999). Because the NHANES III and the NHANES 1999–2000 used partial-mouth examination (Kingman and Albandar, 2002), the results presented here could have underestimated the prevalence of periodontitis in both surveys.
Our findings indicate that the prevalence of periodontitis has decreased between the NHANES III and the NHANES 1999–2000. This change was observed across all racial/ethnic groups, with blacks exhibiting the greatest absolute difference. The fact that the change in periodontitis was observed across all covariates is encouraging and could indicate a true decline in periodontitis over time. However, the findings need to be interpreted with caution and confirmed with further data from the ongoing NHANES survey as data become available. Further, given the growing diversity of our society, the periodontal health of other racial/ethnic groups, such as Asians, should be considered in the current discourse of racial/ethnic disparities.
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ACKNOWLEDGMENTS |
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Received October 11, 2004; Last revision February 23, 2005; Accepted May 20, 2005
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REFERENCES |
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