Obesity in children has dramatically increased over the past three decades with an estimated one in four children in the United States being "at risk" for overweight (BMI > 85th percentile) and eleven percent obese (BMI> 95th percentile) (Nicklas et al, 2003). In 1999, 13% of children aged 6 to 11 years and 14% of adolescents aged 12 to 19 years in the United States were overweight. This prevalence has nearly tripled for adolescents in the past 2 decades (Surgeon General, 2004). Obesity has far-reaching consequences and complications including psychosocial issues, hyperlipidemia, glucose intolerance, non-insulin dependent diabetes mellitus, hepatic steatosis, cholithiasis, hypertension, polycystic ovarian disease, and sleep apnea (Dietz, 1998).
Dietary and feeding practices have a primary influence on infant growth. The World Health Organization (WHO, 2002) recommended exclusive breast feeding up to or beyond 2 years of age. Recommendations were not given on introduction of solid foods for formula fed infants even though there is evidence that introduction before 4 months of age may be associated with increased body fat, higher BMI, increased incidence of respiratory illness in later childhood and increased risk for Early Childhood Caries (ECC). A significant relationship was identified between reported weaning practices and ECC in over 1000 Hispanic children of women participating in the Women, Infant's and Children Supplemental Feeding Program (WIC) in South Texas suggesting that feeding practices may modulate the incidence of ECC (Garcia-Godoy, Mobley, & Jones, 1995).
The Dietary Guidelines for Americans (Johnson & Frary, 2001) identify sugar as a significant factor in the development of dental caries. The frequent, long-term use of baby bottles containing fermentable sugars is associated with ECC (Fitzsimons, Dwyer, Palmer, & Boyd, 1998). Children between the ages of 5 and 8 who consumed sweet snacks between meals were five times more likely to have decayed, missing or filled teeth than those children who consumed fewer sweet snacks (Kalsbleek & Verrips, 1994). The increase in obesity during the last decade has come largely from increased carbohydrate consumption (Anand & Basiotis, 1998). This increased carbohydrate consumption in children has been attributed to increased sweetened soft drink consumption among children (Morton & Guthrie, 1998). Soft drink consumption has been shown to contribute to childhood obesity in that for each serving of soft drink consumed, the odds of becoming obese increased by 60% (Ludwig, Peterson & Gortmaker, 2001). The American Academy of Pediatrics has issued a Policy Statement on Soft Drinks in Schools (2004). Their policy statement calls for the elimination of soft drinks in schools, citing the increased risk for obesity and dental caries in children from the consumption of soft drinks.
This study identified interactions between caries experience and Body Mass Index (BMI) in children participating in a Women, Infants, and Children (WIC) Supplemental Feeding Program in South Texas. These data were collected as a sub-project within a larger study designed to examine the parent-child interface with environment and food procurement processes relative to risk for obesity.
Health Outcomes of ECC
The simultaneous presence of cariogenic microorganisms, fermentable carbohydrate, and a susceptible tooth and host initiate the infectious and transmissible disease known as dental caries in adults and ECC in children. At a microscopic level, the biology of caries is the same for adults and children. However, in children this disease can have a negative impact on a child's diet, nutritional status, sleep patterns, psychological status and later on, school attendance. Children have been reported to experience pain with ECC that adults would not endure. ECC has been described as a virulent form of caries that starts soon after teeth erupt and it proceeds rapidly to involve primary molars and canines (Davis, 1988).
Children who develop ECC are more likely to experience delayed growth and development. Several interventions for ECC have been identified in the literature as important for the amelioration of commonly coexisting conditions of ECC and growth faltering (Fitzsimons, et al., 1998; Elise & Field, 1990). Acs, Eodolini, Shulman, & Chussid, (1998) found that correcting ECC could lead to an accelerated velocity of weight gain, resulting in the improvement of the growth in the children. Because ECC has been closely associated with underlying nutritional deficiencies in the perinatal period (Davis, 1988) it is likely, as the disease progresses, that developmental eating behaviors and nutritional status are threatened.
Bottle use was significantly associated with obesity (>95th% BMI, p<0.0005), not significant with overweight (>85th% BMI, p<0.06) and statistically significant with iron deficiency anemia in Hispanic and African American children ages 18-56 months who were assessed in an East coast study (Bonuck & Kahn, 2003). Likewise, bottle use in infancy has been associated with increased risk of early childhood caries (Curzon & Preston, 2004). This suggests that an interaction exist between BMI and caries experience in infants and children and that infant and child feeding practices may be a primary mediator in both obesity and caries.
The prevalence of overweight among children in the United States is continuing to increase, especially among Mexican-American and non-Hispanic black children. Overall there are substantial racial differences in the prevalence of overweight for children and adolescents (Hass et al., 2003; Ogden, Regal, Carroll, & Johnson, 2002). Obesity appears to be a central mediator for many chronic diseases and it is possible early childhood caries may be one that is also associated with the current obesity epidemic.
ECC occurs frequently in children who are given nursing bottles of milk, juice or other sweetened beverage frequently during the day or night (Surgeon General, 2000). Dental caries is a common childhood disease, five times more common than asthma (Surgeon General, 2000). Low income children suffer more from dental caries than do more affluent children. Nearly 37% of low income children ages 2-9 have ECC compared to 17% of children from families not below the poverty level. Hispanic children have disproportionately higher prevalence for early childhood caries (ECC) than do other ethnicities (Flores et al., 2002). Mexican American children who reside in families below the poverty level have the highest rate of ECC, averaging 2.5 decayed teeth per child, compared to poor African American children (average of 1.5 decayed teeth per child) or poor white children (average of 1.9 decayed teeth per child) (Surgeon General, 2000). Obesity and ECC are both diet-based conditions in that they share a cause: excessive ingestion of fermentable carbohydrates. Studies show that children with poorer diets have a higher prevalence of dental caries. Moreover, children with higher incidences of dental caries have an increased number of risk factors for cardiovascular disease (Larsson, 1992; Larsson, 1995). As with obesity, the reduction of dental caries has also been targeted as on of the goals for Healthy People 2010. The health objective is to further reduce the incidence of dental caries in all age groups through public health initiatives and improved access to care (DATA, 2001). Reports are emerging of a relationship between obesity and dental caries, with the suspected link being a diet high in fat and sugar (Martin-Iverson, Pacza, Phatouros, & Tennant, 2000).
Obesity and Adult Oral Health
Few studies have been done to establish if a relationship between dental caries and obesity exists. Studies in adults with similar conditions may show common pathways for the development of ECC. In 2001, a study conducted in Japan attempted to establish the relationship between obesity and periodontitis (Saito et al., 2001). This study was conducted on 643 healthy Japanese adults. For each subject a measured hip to waist ratio and BMI were calculated. These measurements were compared to a periodontal score determined by trained dentists who conducted an oral exam for periodontal disease on each individual. Multivariate analysis revealed an increased rate of periodontitis in participants with higher categories of BMI and hip to waist ratios.
Another study (Al-Zahrani, Bissada & Borawski, 2003) revealed similar findings. This study was a retrospective review of data collected during the National Health and Nutrition Examination Survey (NHANES III), conducted from 1988 to 1994. Data from a total of 13,665 subjects were analyzed with variables of periodontal score, BMI, waist circumference, age, race, gender, poverty index, education, time since last dental visit, smoking, and diabetes. Results revealed were similar to those of the Japanese study. There was an increased prevalence of periodontitis in the obese subjects in comparison to the non-obese participants.
Both of these studies demonstrate a link between obesity and dental disease, although neither of them examined the relationship of caries specifically nor did they address if this phenomena exists in children. In fact, only three studies have been conducted attempting to illuminate this relationship. Tuomi (1989) conducted a pilot study on obesity and caries prediction in Luvia, Finland between 1972 and 1981. A sample of 516 children ages 5-13 years old were evaluated for the possibility of predieting future decay using obesity and previous caries experience as variables. Data were collected via a retrospective review of files from a local health center. Using Pearson correlations, the author found that obesity alone was not a good predictor of dental decay, nor was a history of previous decay. However, the two variables combined provided excellent prediction for future decayed teeth.
Larsson et al (1995) examined artherosclerosis risk factors in relationship to dental caries. A sample of 199 children aged 15 years old living in an urban community of Northern Sweden were evaluated from 1987-1989. Each child had their blood pressure measured, was weighed and measured for height, examined by one of three trained dentists, had a venous blood sample taken, and kept a five-day food intake diary. Variables from the collected data included BMI, total cholesterol, high-density lipoprotein levels (LDL), triglycerides, BMI, blood pressure, and decayed/filled tooth surfaces score (DFS). Pearson correlations were calculated to establish univariate associations between dental caries and CVD risk factors while multivariate regressions were performed to assess independent effects of CVD risk factors on total dental caries score and BMI. Ultimately, the study found that adolescents with a higher incidence of caries had a higher number of risk factors for cardiovascular disease. More specifically, the participants with a higher caries score tended to have a higher BMI and diastolic blood pressure than those without caries. This study confirms the previous study by establishing that obese patients were found to have higher rates of dental caries.
In contrast, a study done by Chen (1995) attempted to define the relationship between pediatric obesity and dental caries. This study was conducted on 5133 children previously enrolled in a government-sponsored survey in Taipei City, Taiwan. Body measurements of height and weight, calculated BMI, and dental screenings for decayed, missing, and filled teeth were performed. The author ran Pearson correlations based on these measures and concluded that there was no significant relationship between any of the variables. Although discouraging from a preliminary standpoint, the author failed to disclose his study design or methodology stating they were written in Chinese and available only in a monograph for the Taipei City government.
In summary, studies conducted on adults advance the position that obese patients do have a higher incidence of dental disease. However, out of the three studies done with children to determine the same relationship the results were equivocal and only one was done prospectively. Furthermore, only one was conducted with data from participants in the United States with the majority of participants being non-Hispanic whites (Al-Zahrani, et al., 2003).
Hispanic Health Disparities Regarding Oral Health
Hispanics, particularly those of Mexican descent, are the largest and fastest growing ethnic minority group in the United States. Furthermore, Hispanics show a higher prevalence of disease and lower utilization of health services (Pollick, Pawson, Martorell, & Mendoza, 1991). Hispanic children are significantly more likely to have sub-optimal health status, spend more days in bed for illness, and make fewer physician visits than their non-Hispanic white counterparts (Flores, et al., 2002). Both international and national studies have shown that Mexican-American children in particular have higher rates of obesity than their other Hispanic counterparts and ethnic minorities (Dwyer, et al., 2000; Martorell, Khan, Hughes, & Grummer-Strawn, 1998). Moreover, according to the Hispanic Health and Nutrition Examination Survey (HHANES), Hispanic children had a higher incidence of dental disease than both non-Hispanic whites and black children (Ismail, 1997), a trend that still continues today. Among younger children aged 2 to 4 years old, Mexican-Americans were more likely than whites or blacks to have caries, untreated disease, and decayed or filled tooth surfaces (Kaste, Drury, Horowitz, & Beltran, 1999).
The reasons for disparities in oral health are unclear. Studies have shown that minority children do experience more decay than their white peers. Furthermore, Mexican-American children are less likely to have visited a dentist or had their teeth cleaned (Nurko, Aponte-Merced, Bradley, & Fox, 1998). Paradoxically, 61% of Hispanics have dental coverage from Medicaid or statefunded Children's Health Insurance Programs (CHIPS) (Edelstein, 2002). Clearly the barriers that drive these disparities need to be illuminated. Common practices that mothers within the Hispanic community do such as adding sugar or sweet substances to milk in the bottle or allowing the child to fall asleep with the bottle in the mouth are well documented (Flores, et al., 2002). However, what role these practices other cultural phenomena have in promoting or lessening decay need to be clarified.
The sample consisted of 104 children between the ages of one and two years old who were enrolled in the Special Supplemental Nutrition Program for Women, Infants and Children (WIC) in a large Southwestern city. The children were of Mexican American ethnicity and measured at or above the 95th percentile weight for height to be included in the study. The children were enrolled in one cohort of a three cohort study examining growth in children in WIC. The other two cohorts consisted of normally growing children (between the 25 percentile and the 75th percentile in weight for height) or growth stunted (below the 5th percentile in height). The enrolled children lived with one or both parents, were born at full term after an uncomplicated prenatal course, and did not have a history of any organic or systemic causes for their obesity. The children were enrolled when they were present in the WIC clinic for their biannual WIC certification. Their mothers were approached by a member of the research team who explained the study and obtained informed consent if the mothers agreed to participate and their children qualified based on the above criteria. The consent form and study protocol were approved by the appropriate university IRB and the health department IRB before the study commenced. see Table 1 for the description of the sample.
Data Collection and Instruments
Data were collected by nurses and nutritionists following the study protocol. Data were obtained on the child's size, the child's oral health by examination, and the mother's perception of the child's oral health needs. The mother's perception was obtained through the Oral Health Needs Assessment Scale. This instrument has been used in previous community based studies of oral health needs (Louie, Brunelle, Maggiore, & Beck, 1990), and indicates how long (if ever) since the child visited a dentist; the reason for the dental visit; any existing need for dental care; and if needed dental care had been obtained. To obtain the anthropometric measures, the child was weighed on a balance beam scale and measured by a stadiometer while supine. The child was weighed wearing only a dry diaper and measured with bare feet. The measurements were placed into the formula for BMI for interpretation ( see below).
BMI: Body Mass Index
Calculation of Body Mass Index (BMI) for Children English Formula: BMI = [Weight in pounds ÷ Height in inches ÷ Height in inches] x 703; Example: A 33 pound 4 ounce child is 37 5/8 inches tall 33.25 pounds divided by 37.625 inches, divided by 37.625 inches x 703 = 16.5.
Metric Formula: BMI = Weight in kilograms ÷ [Height in meters]2
Or BMI = [Weight in kilograms ÷ Height in cm ÷ Height in cm] x 10,000;
Example: A 16.9 kg child is 105.2 cm tall. 16.9 divided by 105.2 cm divided by 105.2 cm x 10,000 = 15.3 BMI.
Weight for Height Percentile:
Growth charts for boys and girls, birth to 36 months, developed by the National Center for Health Statistics and the National Center for Chronic Disease Prevention and Health Promotion were used to plot weight-for-height percentiles.
Oral Health Examination:
Caries experience was defined as any current or past history with ECC and was scored as 0 = negative; 1 = positive. Any evidence of decayed, missing or filled teeth was considered positive for caries experience. Early childhood caries were also recorded and the current state of the children's teeth was scored. Dental professionals (community dentist and community dental hygienist) from the Department of Community Dentistry at a local dental school conducted trainings with the nurses and nutritionists conducting the study to assure for inter-rater reliability in the assessment of caries experience. Visual cues were provided using a Reference Guide for Screening Preschool Children. The screening consisted of examination of the upper and lower central incisors and any molars that were present. The screenings were done using ambient light and penlight. No probing was done with any instruments. The following scores were assigned to the oral exam for early childhood caries:
0 = no evidence of caries experience;
1 = white spots present on teeth (evidence of demineralization, the precursor to frank caries)
2 = filled teeth (evidence of history of caries)
3 = brown spots present on teeth (evidence of frank caries).
This scoring allowed for current caries to receive the highest score as it indicates a current, unmet need for dental services. The mothers were also asked to describe the condition of their children's teeth where 1= excellent, 2 = very good, 3=good, 4= fair, 5= poor. They were also asked if they had any kind of insurance that would cover dental care (1=no, 2= yes). If they had not received dental care for their children, they were asked what the main reasons they could not get care were. Eleven reasons were provided, ranging from finances (could not afford, no insurance, no acceptance of Medicaid, no transportation) to resources issues (not know where to go, could not get appointment, hours not convenient, too long of wait at appointment, language barriers).
Pearson's correlations were used to determine the degree to which measures of BMI were related to measures of ECC and other factors identified in the oral health needs assessment. See Table 2 for the significant relationships. Of the list of items identified by the mothers of reasons they had not obtained dental care for their children, the ones significantly related to ECC were lack of dental insurance, transportation issues, and lack of knowledge of where to obtain dental care for children. The mother's perception of the condition of her children's teeth was also significantly related to the presence of ECC. The variables of 1) mother's perception of condition of children's teeth; 2) lack of transportation for dental care; 4) Oral Health Needs Assessment scale (OHNA); and 4) child BMI were entered into a hierarchical multiple regression equation with the dependent variable being level of early childhood caries. all variables entered and were significant predictors. The model for predicting level of early childhood caries was accepted (adjusted R2 =.21; F = 7.13; p=.000).
The mothers' assessment of the condition of their children's teeth was significantly related to the results of the screening examinations. Including questions on the child health history form about the condition of the child's teeth and the child's dental care provider can be triggers for further exploration of the issue of need for dental care. In this study, the children who were receiving adequate dental care, as indicated by the Oral Health Needs Assessment also had dental insurance. The children without dental insurance were significantly more likely to have ECC. Many states are removing dental care from their basic package of health coverage provided through Medicaid and the Child Health Insurance Program. The future lack of dental coverage will surely result in more children lacking adequate care for oral health.
Lack of resources was also associated with ECC, in that the children did not receive care for their teeth if the mothers lacked transportation or did not know where to receive care. This lack of knowledge of resources can be addressed by public health professionals who can identify dental professionals in the community who accept Medicaid or allow patients to self pay. Public health professionals can also advocate for dental clinics to be included in public health clinics where primary care is provided, and for oral health care to be recognized as primary health care.
The combination of child BMI, the mother's assessment of the condition of her child's teeth, the lack of transportation and the lack of current dental care or dental insurance (revealed in the Oral Health Needs Assessment) explains a significant part of the development of ECC in low income Mexican American children in this study. These variables represent the child's own food intake and the family's lack of health care resources. Other causes of ECC to be considered are the specific foods the child eats, as high carbohydrate foods encourage the growth of the bacteria that contribute to caries, the feeding pattern the child uses, and the oral health care provided to the child by the mother. The frequent, prolonged use of baby bottles has been associated with the development of ECC, but what remains to be discovered is how to encourage weaning children from the bottle when teeth emerge to prevent the development of ECC. Cleaning the teeth with soft toothbrushes and fluoride toothpaste will also prevent the development of ECC. Methods to encourage parents to provide oral health care to their infants and children also need to be tested for their efficacy and cultural utility.
Infants and children participating in federal supplemental feeding programs who present with higher BMI measures may be at increased risk for dental caries, more specifically Early Childhood Caries (ECC). If multi-factorial mediators of chronic and infectious diseases are identified, interventions can be inclusive of these measures to address these specific issues. Additionally, public health venues can be targeted to significantly reduce the social and economic burden of caries and obesity. Implications suggest need for development and validity of oral health education within prenatal and early childhood education and offered synchronously with programs targeting improved nutrition and decreased risk of obesity.
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