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RESEARCH REPORT |
1 Department of Dental Public Health Sciences, University of Washington, B509, 1959 NE Pacific Street, Box 357475, Seattle, WA 98195-7475, USA;
2 Department of Epidemiology, Social Medicine Institute, State University of Rio de Janeiro, Brazil
* corresponding author, silvajcc{at}u.washington.edu
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS & METHODSStatistical AnalysesRESULTSDISCUSSIONREFERENCES |
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KEY WORDS: socio-economic position • trends • poverty • health disparities • socio-economic disparities
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS & METHODSStatistical AnalysesRESULTSDISCUSSIONREFERENCES |
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Edentulism, or complete tooth loss, is the ultimate marker of disease burden for oral health. The extent to which the effects of socio-economic disparities on edentulism have increased, decreased, or remained unaltered over the last decades has not been reported. Edentulism is mostly the result of caries and periodontitis, and has the potential to affect an individual’s quality of life significantly (Mack et al., 2005). The aim of this study was to investigate socio-economic disparities in edentulism between 1972 and 2001, by comparing differences in the edentulism prevalence between individuals from low and high socio-economic positions (SEP) of the US population in 1972, 1991, and 2001.
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MATERIALS & METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS & METHODSStatistical AnalysesRESULTSDISCUSSIONREFERENCES |
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The number of teeth was assessed by trained dentists during oral examination. A person was considered edentulous if 28 teeth were missing (excluding third molars). The socio-economic position (SEP) was determined based on the Poverty Index and the cut-offs suggested in the guidelines of the NHANES III (NCHS, 1996). The Poverty Index is the ratio of total family income to the Federal poverty level, which is computed by the US Census Bureau (2005). An individual reporting on the questionnaire family income less than or equal to 130% of the Federal poverty level was classified as low-SEP. The most advantaged social group was considered the reference group for comparisons (Braveman, 2006), and those reporting a family income greater than 350% of the Federal poverty level were classified as high-SEP. The middle-SEP population (family income between 130% and 350% of the Federal poverty level) was included in the analyses, but the results are not reported in this study. Questionnaires provided information on other sociodemographic and lifestyle indicators, such as age, gender, race, education, smoking history, and dental care utilization.
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Statistical Analyses |
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TOPABSTRACTINTRODUCTIONMATERIALS & METHODSStatistical AnalysesRESULTSDISCUSSIONREFERENCES |
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The variance estimation was based on the information that the primary sampling units were sampled independently in each of the surveys, and the Taylor-series linearization method with replacement was used (Korn and Graubard, 1999). Since the NHANES surveys were done at different times, the original sampling weights were used in the analyses. Analyses were performed with the contrast statement of the descript procedure of SAS-callable SUDAAN software.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS & METHODSStatistical AnalysesRESULTSDISCUSSIONREFERENCES |
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).
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). When stratified by age groups, the prevalence of edentulism decreased for all age groups of low-SEP individuals during 1972 and 2001. Edentulism prevalence also decreased for the other low-SEP subgroups, defined by gender, race, education, dental utilization, and smoking, except for low-SEP former-smokers. The prevalence of edentulism did not decrease for this latter low-SEP subgroup (14.5% in 1972 and 2001) (Table 2).
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Low-High-SEP Disparities in Edentulism Prevalence: 1972–2001
Main Results
Differences in edentulism prevalence between low- and high-SEP did not change significantly from 1972 to 2001 (p = 0.480). Compared with high-SEP individuals, the prevalence of edentulism in low-SEP individuals was 10.6 percentage points (pp) higher in 1972, 12.1 pp higher in 1991, and 11.3 pp higher in 2001 (Table 3).
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Smoking Status
Smoking status altered the effect of SEP on edentulism. The prevalence difference between low- and high-SEP individuals decreased marginally significantly by 5.1 pp among never-smokers (11.1 to 6.1). SEP disparities increased significantly by 7 pp among former smokers (5.2 to 12.2). No significant changes occurred in current smokers (an increase of 1.7 pp from 12 to 13.7) (Table 3).
Dental Care Utilization
Similarly, dental care utilization modified the effect of SEP on edentulism. For those not using dental care in the prior year, the edentulism prevalence difference increased significantly by 6.9 pp (3 to 9.9) from 1972 to 2001. In contrast, for those reporting dental care utilization, the SEP disparities in edentulism decreased significantly by 8.9 pp (13.7 to 4.8) in the same period (Table 3).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS & METHODSStatistical AnalysesRESULTSDISCUSSIONREFERENCES |
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Exploratory subgroup analyses suggested that positive trends toward reducing socio-economic disparities in edentulism occurred among those adults reporting a dental visit and those adults reporting never having smoked. Regular dental visits have been associated with reduced risk of tooth loss (Cunha-Cruz et al., 2004), and changes in dental practices during the past century have produced more treatment alternatives to tooth extraction (Eklund, 1999). Although universal access to dental care, by either free access or health insurance, may not eliminate socio-economic disparities in tooth loss (Gilbert, 2005; Neto and Nadanovsky, 2006), our findings suggest that, for the population reporting dental care utilization, socio-economic disparities in edentulism were reduced. Smoking increases the risk of tooth loss (Krall et al., 1997) and can be associated with other unhealthy lifestyles (Fine et al., 2004). Smoking prevalence has decreased considerably in the last decades (CDC, 2005), but this trend has not reached all socio-economic positions in the United States. These findings suggest that smoking avoidance had a positive secular effect on disparities and may still have the potential to contribute substantially to further reductions in socio-economic disparities relative to edentulism.
Trends in socio-economic disparities in edentulism were not drastically different when stratified by education, race, gender, and age. Education provides knowledge and other non-material resources that have been documented to promote health (Galobardes et al., 2006). In this study, we failed to identify positive trends for socio-economic disparities in edentulism among high-school-educated adults. Similarly, one might have expected that minority groups with socio-economic disadvantages might have improved more than other groups, due to health programs targeting these groups. No such trends were observed for low-SEP adults of black race when compared with high-SEP adults of the same race. In addition, gender did not influence the secular effect of SEP on edentulism.
Strengths of this analysis were the representative sample of the US population, the assessment of edentulism by clinical examination rather than by self-reports, and the consistent use of the Poverty Index as a socio-economic position indicator over three decades. In contrast to other socio-economic indicators, the Poverty Index reflects the actual cost of living adjusted for family size, age, and inflation, thus facilitating comparisons in different time periods.
Weaknesses of the study included the limited power to assess trends, missing information, and the limited ability to explore causes for socio-economic disparities. Although the number of participants in each survey was large, the inferences for the trends were based on three timepoints, which may have reduced our ability to reach more robust conclusions (as compared with six timepoints, for instance). Missing information for part of the US population is another limitation of this study. The three surveys did not include institutionalized individuals, and the first NHANES did not include individuals older than 74 years. In addition, information on Poverty Index and number of teeth was missing for some participants. About 5% of individuals 65+ years live in long-term-care facilities in the US, less than 6% of individuals were older than 74 years in each survey, and less than 10% of the information was missing. The impact of not including these groups in our estimates of edentulism disparities is unknown.
While the main aim of this study was to examine the secular trends in socio-economic disparities in edentulism prevalence, we attempted to explore causal factors that may be leading to the observed trends. For this secondary objective, the cross-sectional nature of each survey, combined with the lack of information on temporality, limits the interpretation of the results. In addition, socio-economic information was assessed at the time of the interview, and not at the time when it may actually be of significance in determining edentulism. Given the chronic nature of dental diseases and the sometimes lifelong dental health decline toward the ultimate endpoint of edentulism, it is probably unreasonable to expect recent programs aimed at eliminating disparities to show an impact on edentulism. Finally, we assessed only a limited number of potential causes, and other explanatory factors—such as trends in access to fluorides (Provart and Carmichael, 1995; Slade et al., 1996), changes in dental practice (Eklund, 1999), and macro-determinants of health, such as increased survival, socio-economic inequalities, or improved diet—were not explored, due to data limitations.
While lack of power for detecting trends in disparities and limited ability to determine causality are important considerations, analysis of the best available data suggests that socio-economic disparities in edentulism have not changed considerably over three decades. Despite the drastic decrease in edentulism between 1972 and 2001, the effect of socio-economic position on edentulism has remained unchanged. We have evidence suggesting that both dental care utilization and smoking avoidance may hold promise for reducing disparities.
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ACKNOWLEDGMENTS |
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Received March 3, 2006; Last revision October 6, 2006; Accepted October 17, 2006
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS & METHODSStatistical AnalysesRESULTSDISCUSSIONREFERENCES |
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Centers for Disease Control and Prevention (CDC) (2005). Cigarette smoking among adults—United States, 2003. MMWR Morb Mortal Wkly Rep 54:509–513.[Medline]
Cunha-Cruz J, Nadanovsky P, Faerstein E, Lopes CS (2004). Routine dental visits are associated with tooth retention in Brazilian adults: the Pro-Saude study. J Public Health Dent 64:216–222.[ISI][Medline]
Eklund SA (1999). Changing treatment patterns. J Am Dent Assoc 130:1707–1712.[Abstract]
Fine LJ, Philogene GS, Gramling R, Coups EJ, Sinha S (2004). Prevalence of multiple chronic disease risk factors. 2001 National Health Interview Survey. Am J Prev Med 27(2 Suppl):18–24.[ISI][Medline]
Galobardes B, Shaw M, Lawlor DA, Lynch JW, Davey Smith G (2006). Indicators of socio economic position (part 1). J Epidemiol Community Health 60:7–12.
Gilbert GH (2005). Racial and socio economic disparities in health from population-based research to practice-based research: the example of oral health. J Dent Educ 69:1003–1014.
Korn EL, Graubard BI (1999). Analysis of health surveys. New York: Wiley.
Krall EA, Dawson-Hughes B, Garvey AJ, Garcia RI (1997). Smoking, smoking cessation, and tooth loss. J Dent Res 76:1653–1659.
Mack F, Schwahn C, Feine JS, Mundt T, Bernhardt O, John U, et al. (2005). The impact of tooth loss on general health related to quality of life among elderly Pomeranians: results from the study of health in Pomerania (SHIP-O). Int J Prosthodont 18:414–419.[ISI][Medline]
NCHS (1996). National Center for Health Statistics. Analytic and reporting guidelines of the Third National Health and Nutrition Examination Survey, NHANES III (1988–94). Hyattsville, MD: National Center for Health Statistics, Centers for Disease Control and Prevention.
NCHS (2004). National Center for Health Statistics. NHANES Analytic Guidelines. http://www.cdc.gov/nchs/nhanes.htm.
Neto JMS, Nadanovsky P (2006). Social inequality in tooth extraction in a Brazilian insured working population. Community Dent Oral Epidemiol 34: 1–6.[ISI][Medline]
NIDCR (2002). National Institute of Dental and Craniofacial Research. A plan to eliminate craniofacial, oral and dental health disparities. Bethesda, MD: National Institute of Dental and Craniofacial Research.
Provart SJ, Carmichael CL (1995). The relationship between caries, fluoridation and material deprivation in five-year-old children in County Durham. Community Dent Health 12:200–203.[Medline]
Slade GD, Spencer AJ, Davies MJ, Stewart JF (1996). Influence of exposure to fluoridated water on socio economic inequalities in children’s caries experience. Community Dent Oral Epidemiol 24:89–100.[ISI][Medline]
US Department of Health and Human Services (2000a). Healthy people 2010: understanding and improving health. 2nd ed. Washington, DC: US Government Printing Office.
US Department of Health and Human Services (2000b). Oral health in America: a report of the Surgeon General. Rockville, MD.
US Department of Health and Human Services (2003). National call to action to promote oral health. Bethesda, MD.
US Census Bureau (2005). How the Census Bureau measures poverty. http://www.census.gov/hhes/poverty/povdef.html.
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