Journal of Public Health Dentistry . ISSN 0022-4006

Inequalities in dental caries among 12-year-old Chinese children Anqi Shen, MSc1; Xiaojuan Zeng, PhD2; Min Cheng, PhD3; Baojun Tai, BDS4; Ruizhe Huang, MSc5; Eduardo Bernabé, PhD1 1 2 3 4 5

Division of Population and Patient Health, King’s College London Dental Institute at Guy’s, King’s College, and St. Thomas’ Hospitals, London, UK Stomatology Hospital, Guangxi Medical University, Guangxi, China Department of Preventive Dentistry, Stomatology College, Jilin University, Changchun, China Department of Preventive Dentistry, School and Hospital of Stomatology, Wuhan University,Wuhan, China Department of Preventive Dentistry, Stomatological Hospital, Xi’an JiaoTong University, Xi’an, China

Keywords socioeconomic factors; dental caries; geography; urbanization; child; ethnic groups. Correspondence Dr Xiaojuan Zeng, Affiliated Stomatology Hospital, Guangxi Medical University, 10 ShuangYong Road, Nanning, Guangxi Province 530021, China. Tel.: +86 (0) 77-5358348; Fax: +86 (0) 771-5335367; E-mail: [email protected]. Anqi Shen and Eduardo Bernabé are with the Division of Population and Patient Health, King’s College London Dental Institute. Xiaojuan Zeng is with the Stomatology Hospital, Guangxi Medical University. Min Cheng is with the Department of Preventive Dentistry, Stomatology College, Jilin University. Baojun Tai is with the Department of Preventive Dentistry, School & Hospital of Stomatology, Wuhan University. Ruizhe Huang is with the Department of Preventive Dentistry, Stomatological Hospital, Xi’an JiaoTong University. Received: 8/29/2014; accepted: 1/26/2015.

Abstract Objective: To explore whether there are socioeconomic, ethnic, and geographical inequalities in dental caries among 12-year-old Chinese children. Methods: Data from 2,307 12-year-old children living in Guangxi, Hubei, Jilin, and Shanxi and who participated in the Third National Oral Health Survey in China were used for this study. Data were collected through structured questionnaires and clinical examinations with children. The decayed, missing, and filled permanent teeth (DMFT) index and number of decayed teeth (DT) were the outcome measures for analysis. Inequalities in DMFT and DT by socioeconomic position (parental education), ethnicity, and geography (province of residence and urbanicity) were assessed in unadjusted and adjusted negative binomial regression models. Results: Ethnicity and geographical factors, but not parental education, were significantly associated with childhood dental caries in unadjusted models. However, only geographical factors remained significantly related to dental caries after mutual adjustments. The DMFT index and DT were higher among children living in Jilin and Guangxi than those of children living in Hubei and Shanxi, and also higher among children living in rural areas than in those living in urban areas. Conclusion: This analysis shows inequalities in dental caries among 12-year-old children in four provinces of China. There were considerable inequalities in children’s DMFT and number of decayed teeth by geography but not by ethnicity or parental education.

doi: 10.1111/jphd.12091 Journal of Public Health Dentistry 75 (2015) 210–217

Introduction China is divided in 31 provinces, each having a capital city, several large cities, and rural areas (1). China is a multilingual state, which officially has 55 ethnic minorities in addition to the Han majority (2). These minorities (non-Han groups) are distributed across the country, but the majority live in inland or border districts in the less developed Western regions. They are culturally and linguistically diverse, speaking over 80 languages, of which 30 have distinct written forms (3). China has enjoyed sustain economic development over recent 210

decades, which has been accompanied by increase in urbanization (4,5). Caries levels in 12-year-old children are very low in China (6). According to the Third National Oral Health Survey in China, the mean decayed, missing, and filled permanent teeth (DMFT) index of 12-year-olds decreased from 1.03 in 1995 to 0.53 in 2005, and the prevalence of dental caries decreased from 41 to 29 percent within the same period (7). However, about 89 percent of carious teeth in 12-year-olds were left untreated (6,7). These findings contrast sharply with those found in most developed countries where the DMFT in © 2015 American Association of Public Health Dentistry

A. Shen et al.

12-year-olds is somewhat higher (8), but past (treated) caries represents the main DMFT component (9). More importantly, dental caries is still overrepresented in certain groups of the Chinese child population (1,2). Some population-based studies have explored inequalities in dental caries among 12-year-old children in China (1,1014). Most have focused on geographical inequalities (1,1012), showing clear disparities by provinces (1), but conflicting results by urbanization, with some studies showing higher DMFT among children in rural areas (10,11) while one, using the Second National Oral Health Survey data, showing no such differences after adjustments for behavioral factors (12). There is also some evidence that parental education was not related to children’s DMFT in multivariable models (11). Finally, two studies have shown that caries prevalence was higher in ethnic minorities than in Han children (13,14), although DMFT scores were not different between ethnic groups in one of those studies (14). No previous study has explored social, ethnic, and geographic inequalities in childhood dental caries simultaneously. To fill this gap in knowledge, a study was planned to explore whether there are socioeconomic, ethnic, and geographical inequalities in dental caries among 12-year-old Chinese children.

Methods Study population This study used data of part of the Third National Oral Health Survey of China, which was carried out in 2005 covering the four WHO index ages, namely 5-, 12-, 35- to 44-, and 65- to 74-year-olds (7). Data from 12-year-old children living in Guangxi, Hubei, Jilin, and Shanxi provinces were analyzed. Participants were selected from schools using multistage stratified cluster sampling. For selection, every province was divided into urban and rural areas; urban areas were classified into three strata by population size, whereas rural areas were classified by gross domestic product. One city or county was randomly selected from each stratum. Hence, three cities from urban areas and three counties from rural areas were selected from each province. For the next level, three streets or townships were randomly chosen from every city or county. Then, two schools were selected as research sites. From each site, 20 children aged 12 years were randomly selected (7). The four provinces were chosen based on data availability, and although the study sample is representative of the four provinces, it is not representative of the entire population of 12-year-old children in the country. Guangxi is located in South Central China, has a population of 47 million people (40 percent urban, 62 percent Han), and a water fluoride concentration of 0.1-0.2 mg/L. Hubei is located in the Eastern part of Central China, has a population of 58 million people (53 percent urban, 96 percent Han), and a water fluoride con© 2015 American Association of Public Health Dentistry

Inequalities in dental caries in Chinese children

centration lower than 0.5 mg/L. Jilin is located in North Eastern China, has a population of 44 million people (54 percent urban, 91 percent Han), and a water fluoride concentration of around 1 mg/L. Finally, Shanxi is located in Northwest China, has a population of 36 million people (51 percent urban, 99.7 percent Han), and a natural concentration of fluoride in water higher than 1 mg/L in some areas.

Data collection Data were collected through structured questionnaires and clinical oral examinations. The questionnaire collected information on family characteristics and children’s dental behaviors, snacking habits, oral health knowledge and sources of that knowledge, health-seeking behavior, and the impact of oral health on quality of life. Parental education was the only family socioeconomic measure collected for this age group. The education level of each parent was collected separately using single questions with nine response options (illiteracy, primary school, middle school, high school, technical secondary school, junior college, bachelor, master’s and above, and others). Parental education was indicated by the highest level of education attained by either parent and regrouped into four categories: elementary, middle school, high/ technical school, and college or above. Children’s ethnicity was self-assigned using a list of officially recognized ethnic groups in China. Dental behaviors included last dental visit, toothbrushing frequency, and sugar intake frequency. Children reported their last dental visit on a 5-point response scale (never, 2 years ago, within 1 and 2 years ago, within 6 and 12 months ago, less than 6 months ago), toothbrushing frequency on a 3-point response scale (not every day, once a day, and twice a day), and intake frequency of five sweets and snacks (biscuits, cake, or sweet bread; candy or chocolate; sugared water; soft drinks; and fruit juice) on 7-point response scales (twice or more a day, once a day, two to six times a week, once per week, one to three times per month, seldom or never, and others). For sugar intake frequency, each sugary item was assigned a score as follows: twice or more a day (2), once a day (1), two to six times a week (2/7 days = 0.28), once a week (1/7 = 0.14), one to three times per month (1/30 = 0.03), seldom (0) and never (0). Weighted scores were chosen to match the lower frequency of consumption of each response category (15). Weighted scores of the five sweets and snacks were then added to produce an overall score, ranging from 0 to 10. Children’s sugar intake frequency was finally grouped into three categories: less often than daily, up to four times a day, and more than four times a day (16). Clinical examinations were carried out under artificial light using plane mouth mirrors and a standard WHO/CPI probe. Dental caries was diagnosed according to the World Health Organization criteria (17). To ensure the reliability 211

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A. Shen et al.

and validity of the data collection, a pilot survey was conducted in Wuhan city, Hubei province. Unified trainings and calibrations were provided to survey examiners. For reliability assessment, duplicate examinations were conducted during the main survey. Five percent of the participants were re-examined to calculate interexaminer reliability using Kappa statistics. The overall Kappa score for the full survey was 0.92 among 12-year-olds. By provinces, Kappa scores varied between 0.89 and 0.91 in Shanxi, 0.80 and 1.00 in Jilin, 0.90 and 1.00 in Hubei, and 0.79 and 0.90 in Guangxi (7). The number of decayed teeth (DT) and the DMFT index were the outcome measures for this study.

Mann–Whitney test when there were two groups and the Kruskal–Wallis test when there were three or more groups for comparison. Inequalities in DMFT and DT by parental education, ethnicity, province of residence, and urbanicity were assessed in negative binomial regression models as the two outcomes were count variables with overdispersion. Rate ratios were therefore reported. The association of each factor with DMFT and DT was assessed in unadjusted and adjusted models. The adjusted models included socioeconomic, demographic, geographical, and behavioral factors as explanatory variables. Multilevel modeling was deemed inappropriate for this analysis due to the limited number of areas being analyzed (i.e., only data for four provinces were available). However, sensitivity analysis showed that results from multilevel models (not reported) were identical to those found with negative binomial regression.

Statistical analysis We initially compared the socioeconomic, demographic, and behavioral characteristics of the sample by provinces using the chi-squared test. The DMFT index and DT were then compared by socioeconomic (parental education), demographic (sex and ethnicity), geographical (province and urbanicity), and behavioral factors (last dental visit, sugar intake frequency, and toothbrushing frequency) using the

Results Of the 2,307 12-year-old Chinese children who participated in the Third National Chinese Survey in Hubei, Jilin,

Table 1 Characteristics of the Analytical Sample, Stratified by Provinces (n = 2,226) Hubei (n = 1074) Explanatory variables Sex Male Female Ethnicity Han Non-Han Parental education Elementary school Middle school High school College or above Urbanicity Urban Rural Toothbrushing frequency Less often than daily Once a day Twice or more a day Last dental visit Never More than a year ago Within the last year Sugar intake frequency Less often than daily ≤4 times a day >4 times a day

Jilin (n = 389)

Guangxi (n = 378)

Shanxi (n = 385)

n

%

n

%

n

%

n

%

536 538

50 50

196 193

50 50

186 192

49 51

196 189

51 49

896 178

83 17

373 16

96 4

214 164

57 43

383 2

99 1

147 511 349 67

14 48 32 6

58 152 132 47

15 39 34 12

71 151 137 19

19 40 36 5

43 166 130 46

11 43 34 12

536 538

50 50

173 216

45 55

154 224

41 59

174 211

45 55

185 753 136

17 70 13

103 202 84

26 52 22

23 235 120

6 62 32

141 172 72

36 45 19

617 298 159

57 28 15

158 153 78

41 39 20

193 122 63

51 32 17

187 114 84

48 30 22

625 398 51

58 37 5

176 176 37

45 45 10

193 154 31

51 41 8

195 166 24

51 43 6

P value* 0.970

Inequalities in dental caries among 12-year-old Chinese children.

To explore whether there are socioeconomic, ethnic, and geographical inequalities in dental caries among 12-year-old Chinese children...
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