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Obesity and Dental Caries in Children Aged 2-6 Years inthe United States: National Health and NutritionExamination Survey 1999-2002

Liang Hong, DDS, MS, PhD; Arif Ahmed, BDS, PhD, MSPH; Michael McCunniff, DDS, MS;

Pam Overman, EdD; Moncy Mathew, DDS, MPH

Abstract

Objective: This study assessed the associations between obesity and dental

caries in young children participating in a national survey. Methods: Participantsincluded 1,507 children aged 2-6 years who received dental examinations and hadat least 10 primary teeth in the National Health and Nutrition Examination Survey

1999-2002. Decayed/filled teeth (dft) counts of primary dentition were obtained, andweight and height were measured. Body mass index (BMI; kg/m2) was calculated,

and participants were categorized using age- and gender-specific criteria as under-weight (85th and

5 dft. When caries experience was compared across BMI categories stratifiedby age and race characteristics, statistically significant association between cariesand obesity was found only for 60-

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environmental, and lifestyles issues.Nevertheless, childhood obesity andcaries may share some common riskfactors. For example, children at thehighest risk for dental caries are dis-proportionately from minority house-holds and/or live in poverty (1), andchildhood obesity is also associated

with low socioeconomic status (SES)in the United States (13).

Since very few studies haveexplored this issue using large-scalenational samples, the aim of ourstudy was to assess the associationsbetween obesity and dental caries inchildren aged 2-6 years (24 to 5 dft. Thefilling component represented atooth surface that has been restored

with either a permanent or a tempo-rary restoration as a result of caries.Because of difficulty of correctly dis-tinguishing among teeth extractedfor caries and other reasons, such asexfoliation and trauma, missing teethcount was not included in this analy-sis. Further, using criteria from the

American Academy of Pediatric Den-tistry, severe early childhood caries(S-ECC) was defined as follows: anysign of smooth surface decay in chil-dren younger than 3 years of age;one or more decayed or filled sur-faces in primary maxillary anteriorteeth from ages 3 to 5 years; ordfs4 (age 3), 5 (age 4), or 6(age 5) (14).

Weight and height were measuredduring a physical examination.

Weight was measured when the childstood on a digital scale that wasconnected to the Integrated SurveyInformation System (ISIS) and stand-ing height was measured with anelectronic stadiometer that was alsoconnected to the ISIS. BMI was cal-culated using the standard formula:

weight in kilograms (kg) divided byheight in meter squared (m2). Chil-dren were classified into four catego-ries using age- and gender-specificcriteria recommended by the Centersfor Disease Control and Prevention(15): underweight less than 5thpercentile; normal weight 5th per-centile to less than 85th percentile; atrisk of overweight 85th to less than95th percentile; and overweight equal to or greater than the 95thpercentile. Dietary variables includedin this analysis were daily totalenergy (kcal) intake, daily total car-bohydrate intake, daily total fatintake, and daily total sugar intake.Dietary data were collected bytrained and calibrated registereddietitians through 24-hour recallinterviews to estimate the intake offood energy, nutrients, and nonnutri-ent food components from foodsand beverages consumed during the24-hour period (from midnight to

midnight) prior to the MEC examina-tions (16).Individual characteristics were

categorized and presented as per-centages or means (standard error).c

2 analyses and KruskalWallis testswere used to compare social-demographic, dietary, medical, anddental variables between cariesexperience categories and amongBMI categories. c2 test was usedto test for categorical associationsbetween caries prevalence and BMI

categories after stratifying by age andrace. Further, BMI categories werecompared between caries-free chil-dren and those with S-ECC using c2

test after stratifying by age, race, andgender. Logistic regression models

were developed to predict cariesexperience (yes/no). The modelincluded the variables that weresignificant in bivariate analyses orthought to be potentially important:childs BMI category, childs age,

Journal of Public Health Dentistry228

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childs carbohydrate intake, race, andfamily income. All statistical tests

were conducted in SAS 9.1 at the0.05 level of significance. TheNHANES Analytic and ReportingGuidelines were followed to apply

appropriate weighting methodologyfor adjustment for the complexsample design and the unequalprobability of selection; the variablesSDMVSTRA, SDMVPSU, and

WTMEC4YR provided with theNHANES 1999-2002 data were usedfor this purpose (14).

ResultsCharacteristics of the 2- to 6-year-

old children are summarized in

Table 1. About 4.2 percent wereunderweight, 73.9 percent hadnormal weight, 11.3 percent were atrisk of overweight, and 10.6 percent

were obese; 42.0 percent had at leastone decayed and/or filled tooth 30.0

percent had one to five dft and 12.0percent had more than five dft; themean number of dft was 1.8 (SE 0.09).

Table 2 presents caries experi-ence and BMI categories accordingto social-demographic, dietary,medical, and dental visit characteris-tics. Overall, there was no statisticallysignificant difference in percentagedistribution of caries experience andBMI categories by gender, PI, race,asthma condition, dental visit in the

previous 12 months, daily totalenergy intake, daily carbohydrateintake, daily fat intake, or daily totalsugar intake. Caries experience (bothpercent of children with caries andthe mean dft score) was comparedacross the BMI categories stratifiedby age and race (Table 3). Generally,

children with at-risk BMI or over-weight BMI had a higher percentageof caries and higher mean dft thanchildren with normal BMI, althoughpercentages and mean dft for BMIcategories varied in different strata.Most of these differences across BMIcategories were not statisticallysignificant, except for percentagesin the 60-

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decayed/filled tooth: yes/no) wasfitted using five predictor variables:age (years), poverty (PI;

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between BMI and caries amongAfrican-American and Hispanic chil-dren might be a reflection of the roleof SES in both conditions.

Considering the results from thisanalysis, it is not surprising that dif-ferent studies (6-11) have observeddifferent relationships, particularly

when samples consisted of local,specific groups of children. Our find-ings, together with those of otherinvestigators, suggest an intricate

Table 3Percentage with Caries and dft by Body Mass Index (BMI)* Category Among Children Aged 2-6 Years

Normal BMI At-risk BMI Overweight BMIP-value

(3 groups)P-value

(2 groups)

Percent of childrenwith caries (SE)

Age 24-

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picture in which many factors maysimultaneously influence the rela-tionship between caries and obesity.

Both obesity and dental caries arecomplex conditions and many bio-logical, genetic, environmental, andbehavioral factors are known to beinvolved in these conditions (19-21).In some developed countries, dentalcaries has been linked to SES factors,such as family income, parents edu-cation and occupation, with low SESindividuals being at higher risk of

caries (2, 17-18, 22). In the UnitedStates childhood obesity is also asso-ciated with low SES (14, 23). Marshallet al. identified measures of SES(parents education and familyincome) that were predictive of bothcaries experience and obesity amongchildren in an Iowa cohort (19). Inour analysis, family income wasidentified as an important predictorof caries experience, after controllingfor age, race, and BMI category.

Additionally, relationships between

health outcomes and contextualcharacteristics particular aspects ofplaces where people live havebeen documented in a number ofempirical studies of various healthconditions (24).Therefore, character-istics of the population, including abroader set of socioeconomic andcontextual characteristics, must beconsidered when the relationshipbetween childhood obesity anddental caries is assessed.

One of the important findings ofthis study was that children at riskof being overweight generally hadhigher caries experience than theirnormal weight peers. This observa-tion is consistent with what otherinvestigators reported (6, 7, 10, 19).

Although the mechanism is not clear,caries co-existed with the risk ofbeing overweight in these studies.Marshall et al. (19) suggested thatneither obesity increases risk ofcaries nor caries increases risk of

obesity, but rather a common riskfactor increased the likelihood ofboth diseases. Dietary factors andSES were hypothesized to becommon risk factors that potentiallylink obesity and dental caries. Adietary habit that contributes toobesity could also increase cariesrisk. It is well established that adietary component is necessary forthe caries disease process. Dietaryhabits (how much and how often thebeverage or food is consumed) can

modify caries risk, with frequentconsumption of sugars consideredto increase the risk. Energy-dense,highly refined food choices anddietary habits have been identified asimportant contributors to the obesityepidemic (25-27). Identification ofchildren at risk of being overweightearly in life may give health careproviders and parents the oppor-tunities for early intervention to de-crease risk for both obesity and

caries. Furthermore, educationalinterventions addressing dietaryissues should highlight both conse-quences (overweight and dentalcaries) simultaneously.

This analysis utilized a nationallyrepresentative sample and thusallowed for greater examination of

complexity in the relationship be-tween obesity and dental caries.However, some limitations must beobserved. Since the data was cross-sectional, causal relationships cannotbe established and the observedassociation could be due to otherunexplored factors. Part of the data

was based on self-reports and thussubject to recall bias. Furthermore,since the reasons for missing teethcould not be explicitly sought,missing teeth were excluded fromthe analysis. This may have excludeda certain number of teeth lost due tocaries.

In conclusion, within study limi-tations, results from this analysis ofa large national sample of youngchildren suggest a complex multi-factorial relationship between child-hood obesity and dental caries. Thisdemands carefully defined researchdesigns, including longitudinalstudies, to identify the particular

pathways through which differentfactors influence dental caries andobesity.

AcknowledgmentWe thank Drs. Teresa Marshall

and Steven Levy for their construc-tive suggestions on data analysis andinterpretation.

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Table 5Logistic Models Predicting Childrens Caries Experience

Outcome variable Predictor var iables Odds rat io (95% CI) P-value

Any decayed and/or filledtooth (yes/no)

Age (years) 1.09 (0.81-1.23) 0.28Poverty index* 0.84 (0.62-1.17) 0.33Overweight 1.20 (0.67-1.03) 0.08Race 1.10 (0.99-1.23) 0.08

Carbohydrate intake 1.02 (0.82-1.17) 0.83Severe early childhood

caries (S-ECC) (yes/no)Age (years) 1.82 (1.43-2.31)

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