|
 
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| REVIEW ARTICLE |
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| Year : 2023 | Volume
: 15
| Issue : 5 | Page : 409-417 |
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Association between parental migration and dental caries of 3-12-year-old children in China: A systematic review and meta-analysis
Sichen Liu1, Angkana Thearmontree1, Virasakdi Chongsuvivatwong2, Shinan Zhang3, Limei Zhang4
1 Improvement of Oral Health Care Research Unit, Community Dentistry Division, Department of Preventive Dentistry, Faculty of Dentistry, Prince of Songkla University, Hat Yai, Songkhla, Thailand
2 Department of Epidemiology, Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla, Thailand
3 Department of Dental Public Health, School of Stomatology, Kunming Medical University, Kunming, Yunnan, China
4 Department of Cardiology, People’s Hospital of Chuxiong Prefecture, Chuxiong, Yunnan, China
| Date of Submission | 18-Apr-2023 |
| Date of Decision | 19-Jul-2023 |
| Date of Acceptance | 19-Jul-2023 |
| Date of Web Publication | 30-Oct-2023 |
Correspondence Address:
Prof. Angkana Thearmontree
Improvement of Oral Health Care Research Unit, Community Dentistry Division, Department of Preventive Dentistry, Faculty of Dentistry, Prince of Songkla University, 15 Karnjanavanich Rd., Hat Yai, Songkhla 90110
Thailand
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/jioh.jioh_89_23
Aim: This review sought to examine the prevalence of dental caries in left-behind children (LBC) and explore the association between parental migration and dental caries among children in China. Materials and Methods: Web of Science, PubMed, the China National Knowledge Infrastructure, Weipu, and Wanfang were searched about the LBC and dental caries in China from 2000 to May 2021. The primary outcome was the prevalence of dental caries in primary and permanent dentition among LBC. The number of children with dental caries among LBC and non-LBC (NLBC) was pooled, and the odds ratio (OR) and 95% confidence intervals (CI) of the relationship between parental migration and children’s dental caries were determined. Result: These included a total sample of 8275 children aged 3–12 years from a total of 11 studies, of which 4547 were LBC and 3728 were NLBC. The pooled prevalence of dental caries among Chinese LBC aged 3–12 years was 64%. Parental migration was significantly associated with the prevalence of dental caries. LBC has a 1.61 times higher risk of having dental caries than NLBC (95% CI: 1.47–1.77). LBC living in the countryside has a higher prevalence (68%) and higher risk of developing dental caries (OR = 1.64; 95% CI: 1.48–1.82) than those living in the city. The prevalence of dental caries is notably elevated among LBC in China. Conclusion: Parental migration stands out as a significant risk factor for dental caries in children aged 3–12 years, particularly in rural or countryside regions. The results call attention to the oral health problems among the LBC. Keywords: China, Dental Caries, Left-Behind Children, Oral Health, Parental Migration
How to cite this article:
Liu S, Thearmontree A, Chongsuvivatwong V, Zhang S, Zhang L. Association between parental migration and dental caries of 3-12-year-old children in China: A systematic review and meta-analysis. J Int Oral Health 2023;15:409-17 |
How to cite this URL:
Liu S, Thearmontree A, Chongsuvivatwong V, Zhang S, Zhang L. Association between parental migration and dental caries of 3-12-year-old children in China: A systematic review and meta-analysis. J Int Oral Health [serial online] 2023 [cited 2023 Dec 9];15:409-17. Available from: https://www.jioh.org/text.asp?2023/15/5/409/388793 |
| Introduction | |  |
Since the 1990s, China is facing an unprecedented increase in rural-to-urban migration due to industrialization, urbanization, and marketization.[1] Many people left their hometowns in the rural areas to work in the urban areas to improve their families’ financial situations.[2] This migration within China was called “internal migration,” which was much more prevalent than international migration.[1]
Left-behind children (LBC) are not the exclusive phenomenon observed in China.[3] Global migration has experienced a significant surge in recent decades, encompassing both international and internal movements. Countries such as Mexico, Sri Lanka, and the Philippines exemplify high rates of international migration. Notably, internal migration exhibits a highly prevalent trend in Asia. In Southeast Asia alone, the number of internal migrants surpassed international migrants by over threefold in 2016 (763 million vs. 244 million).[4] As well as, China stands as a prominent example of a nation with substantial internal migration.[1],[3] These findings underscore the persistent issue of children being left behind, despite varying forms of high migration.
In China, migrants encounter various limitations in accessing numerous facilities due to the absence of permanent residence permission (hukou) in their current place of residence. These constraints extend beyond essential public services such as social security, healthcare, and employment opportunities, encompassing educational opportunities for their children as well.[5] Consequently, in such circumstances, the majority of parents left their children in their hometowns. Typically, the children were looked after by a single parent, grandparents, relatives, or even lived independently. Those children are often called LBC which can be defined as “children under 18 whose parents have been working outside the home for over six consecutive months.”[6] The National Bureau of Statistics of China showed that in 2015 the number of LBC was 68.77 million nationwide, accounts for 25.4% of total children in China, and about 60.0% of them lived in rural areas.[7]
Dental caries represented a highly prevalent public health concern among children, with China’s 4th National Oral Health Survey in 2018 reporting a caries prevalence of 71.9% among 5-year-old Chinese children.[8] Dental caries exert a significant impact on the health and quality of life of children, as it can lead to persistent pain, sepsis, and missed school days, impair academic performance, and further contribute to social inequalities.[9]
Dental caries prevention entails crucial oral health behaviors, including daily tooth brushing with fluoridated toothpaste, regular dental attendance, and sugar consumption restrictions.[9] Parents play vital roles in delivering oral health care and supervising their children’s oral hygiene behavior. Children could learn proper oral hygiene habits from their parents.[10],[11] As a result, the oral health knowledge, attitudes, and practices of parents hold influence over the oral health status of their children. However, children who undergo parental migration and are under the care of individuals other than their parents, such as extended family members, are at risk for several health issues,[12],[13] including dental caries. According to a systematic review conducted in 2018, the health of LBC is adversely affected by parental migration, especially psychological health, and nutrition.[14]
There have been limited studies investigating the association between parental migration and the oral health of the LBC. Most studies were conducted in China and published in the Chinese language. Only one study was published in English.[15] To our knowledge, there is a scarcity of research on oral health among LBC in other countries. Furthermore, the existing studies in China varied in terms of age groups and study areas. Two studies demonstrated a significant disparity in prevalence of the dental caries among LBC, ranging from 37.7% to 89.9%.[16],[17] Moreover, different odds ratios were reported for the association between parental migration and dental caries, such as 1.42[16] and 2.32.[18] Consequently, there is a pressing need to synthesize data from multiple studies to examine the oral health of LBC and identify the effects of parental migration on children’s dental caries.
This meta-analysis aims to enhance comprehension regarding parental migration’s influence on children’s oral health in China, thereby providing initial insights into comparable issues in other countries. The objective of this study is to describe the prevalence of dental caries among LBC in China and examine the association between parental migration and dental caries.
| Materials and Methods | | |
Literature search
This study review adhered to the guidelines outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA).[19] The initial exploration of relevant literature covered publications from the period between 2000 and May 2021. This comprehensive search was conducted using the Web of Science and PubMed databases. Additionally, publications in Chinese were searched based on Chinese primary databases, such as China National Knowledge Infrastructure (CNKI), Weipu, and Wanfang Data. The related master’s and doctoral theses were also included. The search strategy on keywords and medical subject heading (MeSH) terms plus Entry terms was used to expand the range of search [Table 1].
Study selection
Inclusion and exclusion criteria
The inclusion criteria were as follows: (1) published between 2000 and May 2021, (2) primary data collection, (3) samples were LBC aged 0–12 years, (4) dental caries were examined based on the criteria of the World Health Organization or China National Oral Health Survey, and (5) reported dental caries prevalence in the form of decayed, missing, and filled primary teeth (dmft) or decayed, missing, and filled permanent teeth (DMFT),[20] had available abstracts and were published in English or Chinese. The documents that were excluded from the screen encompassed (1) review papers (including literature or systematic reviews), clinical guidelines or recommendations, editorials or reports of expert opinion, and (2) studies specifically designed to validate assessment tools or methodologies.
To establish the eligibility criteria for this systematic review, a Population, Intervention, Comparison, Outcomes, and Study (PICOS) analysis was employed. As the study adopts a cross-sectional design, the exposure was used for intervention (I) and is the parental migration. The comparisons contrasted LBC and non-LBC (NLBC).
Quality assessment/risk of bias
After screening the titles and abstracts of the studies from the search, two reviewers (Bai X and Liu SC) independently reviewed full texts of the potentially relevant papers for the exclusion and quality assessment (risk of bias). Both examiners gave reasons for their decisions. Disagreements were discussed until conclusions were reached. Moreover, the quality assessment was conducted according to the Critical Appraisal Checklist (eight items), for an analytical cross-sectional study of the Joanna Briggs Institute (JBI).[21] Each item has four options: “yes, no, unclear, and not applicable.” The “yes” was scored one, and the others scored zero. The total score was rated into three levels which were “good” (score = 6–8); “fair” (score = 3–5) and “poor” (score = 0–2) [details in Supplementary materials].
Statistical analysis
Prevalence of dental caries
The meta-analysis of proportion was calculated for pooled dental caries prevalence among LBC and the subgroups of age group and areas of study.
Association between parental migration and dental caries
A meta-analysis of dichotomous outcomes was conducted to examine the association between parental migration and dental caries. The data of LBC and NLBC were pooled to calculate the odds ratio and its 95% confidence interval (CI). A Chi-square test with a statistic Q was performed to identify the study heterogeneity (I2). The I2 was defined as the ratio of between-study variance to the observed variance. The interpretation of I2 is as follows: 0%–40%, no or low heterogeneity; 30%–60%, moderate heterogeneity; 50%–90%, substantial heterogeneity; and 75%–100%, considerable heterogeneity.[22] If there is high heterogeneity, the random-effects model would be used. In contrast, the fixed-effects model would be reported in the low heterogeneity studies.[23]
Subgroup analyses were conducted based on age groups and areas of study to identify study heterogeneity and further investigate the study results. Ages were stratified into three groups according to the dentition stage and available data, such as 3–6-year old (primary teeth), 7–12-year old (permanent teeth), and only 12-year old (permanent teeth). The areas of study were stratified according to the administrative levels in China. China has four administrative levels, namely, provinces, cities, counties (districts), and towns.[24] In this study, the two levels/areas were considered as two strata: “city” (provinces) and “countryside” (county, district, and town). Presumptively, the “countryside” level would reflect the rural area, where the “city” would reflect the urban area.
Finally, the overall and subgroup analyses of the primary outcomes were visualized using the forest plot. A sensitivity analysis was conducted to assess the robustness of the assumptions of the conclusions.[25] Based on Egger’s test, a weighted linear regression,[26] was used to identify publication bias. All statistical analyses were carried out utilizing R Statistical Software (version 4.0.5, R Foundation for Statistical Computing, Vienna, Austria).
| Results | | |
Literature search and characteristics of the included studies
The PRISMA flow diagram [Figure 1] shows that 92 papers published between 2000 and May 2021 were initially recruited from the various databases search. Among these, three master theses were included. The interexaminer reliability (Cohen’s Kappa) was 88% indicating good reliability.[27] The reasons for the exclusion were that the studies: (1) did not use dental caries as the primary outcome (seven studies, 44%), (2) did not use the indicated oral examination criteria (six studies, 38%), and (3) did not present the primary outcome (three studies, 19%). Finally, 11 studies were included in this meta-analysis. | Figure 1: A preferred reporting items for systematic reviews and meta-analysis flow diagram for study selection
Click here to view |
[Table 2] summarized the results of the PICOS analysis. This meta-analysis included a total of 4547 LBC subjects and 3728 NLBC subjects from 11 cross-sectional studies. Among these, four studies examined children aged 3–6 years (LBC = 1279 and NLBC = 610), three studies focused on children aged 7–12 years (LBC = 995 and NLBC = 748), and four studies specifically targeted children aged 12 years (LBC = 2273 and NLBC = 2370). The primary outcome for children aged 6 years and below was measured by dmft, whereas those aged 7–12, and specifically 12 years, were assessed using DMFT. Only two studies were done in the city areas, while the other nine studies were in the countryside areas. Stratified random sampling was the predominant method employed in the conducted studies. The quality assessment results revealed that the majority of studies (83%) attained a good rating.
Caries prevalence of left-behind children
[Figure 2] and [Figure 3] show the forest plots of overall and subgroup meta-analysis of caries prevalence among LBC. The overall prevalence of dental caries among LBC aged with 3–12-year old is 64% (95% CI = 0.56–0.71%; I2 = 96%). The subgroup analysis was conducted according to ages and study areas. The prevalence of dental caries in the primary teeth of LBC aged 3–6 years was 76% which was higher than those in the permanent teeth of the other two groups (7–12-year old and only 12-year old) [Figure 2]. [Figure 3] shows that dental caries prevalence of LBC living in the countryside areas was higher than that of those in the city areas (68% vs. 42%). | Figure 2: Pooled prevalence of dental caries in left-behind children by age group
Click here to view |
 | Figure 3: Pooled prevalence of dental caries in left-behind children by area of study
Click here to view |
Effect of parental migration on caries
The forest plot of binary meta-analysis between LBC and NLBC shows the effect of parental migration on dental caries [Figure 4] and [Figure 5]. Parental migration significantly increased the risk of dental caries in children aged 5–12 years 1.61 times (95% CI = 1.47–1.77). The subgroup analyses of three age groups, 5–6-year old, 7–12-year old, and only 12-year old, show similar results [Figure 4]. The highest risk of parental migration on dental caries was observed in children aged 7–12 years, in which LBC has about 1.8 times higher risk of having dental caries than NLBC. In addition, parental migration significantly increased the risk of having dental caries in children who lived in the countryside areas greater than those who lived in the city areas (OR = 1.64 vs. 1.45, respectively) [Figure 5]. Noticeably, I2 values of all binary meta-analyses were low, indicating low heterogeneity. | Figure 4: Forest plot of binary meta-analysis of caries between left-behind children and non-left-behind children by age groups
Click here to view |
 | Figure 5: Forest plot of binary meta-analysis of caries between left-behind children and non-left-behind children according to areas of study
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Influential analysis and publication bias
Influential analysis indicated that the study by Li[16] caused the highest proportion of heterogeneity in the meta-analysis of caries prevalence among LBC. By omitting this study, the I2 decreased from 96.4% to 95.6% which had a minor effect. Therefore, all 11 papers were used in the analysis. According to Egger’s test, there was no significant publication bias among these studies (P = 0.07).[28]
| Discussion | | |
This meta-analysis indicates that approximately 64% of LBC aged 3–12 years had dental caries, and the highest prevalence of dental caries was found in the primary teeth of 3–6-year-old LBC (76%). This prevalence is higher than the prevalence of caries of the children in the corresponding age groups (3–5-year-old children) reported in the latest Chinese National Oral Health Survey in 2015, which was 62.1%.[8] Likewise, the prevalence of dental caries in the permanent teeth of the 12-year-old LBC in this study (54%) was also higher than that in children of the same age reported in the Chinese national survey in 2015 (38.5%).[29] These figures indicate that LBC has a higher caries prevalence in primary and permanent teeth than the general population of the same ages. This evidence was confirmed by the results from the binary meta-analysis that parental migration was a risk factor for developing dental caries in 3–12-year-old children. The result also is consistent with a study conducted in Japan that investigated a similar issue,[30] as well as a recent study published by our team in 2022.[31] The Japan study revealed that children aged 7–8 years living in a single-parent household had a 1.61 times higher risk of having dental caries compared to those living with both parents. In our latest study, we utilized structural equation modeling to examine the independent impact of parental migration on children’s dental caries. Our findings indicated that the effect of parental migration on permanent dental caries was mediated through sugar consumption.
LBC had a higher risk of dental caries than the general population, primarily due to their frequent cohabitation with caregivers who faced numerous limitations. Most nonparental caregivers were grandparents who were of older age and out of date (health beliefs of their generation). Due to physical limitations as well as outdated health knowledge and practice, they typically had low parental skills for their grandchildren’s health.[32] In addition, grandparents in some cultures have wrong parental beliefs and tend to indulge their grandchildren, making them have less control over their health behaviors.[33],[34] All those factors were associated with poor oral health behaviors among children such as high frequent snack consumption and improper tooth brushing.[35] Furthermore, parental migration is usually found among families with low socioeconomic status. Low household income often had a negative impact on the health, especially children. Combining factors of household income and child-rearing by nonparental caregivers exerted a substantial influence on the overall development, and health, including the oral health of children.[36]
The prevalence of caries among LBC aged 3–6 years can be attributed to several factors. These young children heavily rely on parental or caregiver assistance to maintain proper oral hygiene, regulate sweet consumption, and seek dental care.[37] The absence of their parents makes it challenging for LBC to access adequate oral health services, thus contributing to the observed high caries prevalence in this age group.
The highest risk of parental migration on caries was found in 7–12-year-old children (OR = 1.78). At the age of seven, children undergo the eruption of newly formed permanent teeth. These newly erupted teeth are at high risk of dental caries development due to the difficulty of cleaning and incomplete enamel calcification.[38] The family context mentioned earlier increases the vulnerability of the newly erupted permanent teeth to caries development. Additionally, dental neglect is commonly observed among children in the school-age group.[39],[40] Caregivers often hold the belief that children these ages can independently care for their oral health, when in reality, they still require supervision. Guidelines from the Dutch Ivory Cross recommend that children under the age of 10 still necessitate parental care.[41] Moreover, caregivers’ misconceptions, such as “dental disease was not severe” and “having no pain,” act as barriers for children to seek dental care.[39] These barriers are more prevalent among caregivers of LBC than NLBC,[39] resulting in inadequate oral health care practices.
According to this study, LBC who lived in the countryside had a higher percentage of dental caries than those who lived in the city. These results correspond with the 3rd National Oral Health Survey in China which reported that 12-year-old children in rural areas had a significantly increased risk of dental caries compared with those in the urban areas (rate ratio = 1.49).[42] This can be explained by the generally that a rural family is more likely to have a lower socioeconomic status of rural families than the city families.[43] It has been demonstrated that children from low socioeconomic status families have high caries prevalence because of lower oral health knowledge and less proper oral care of their caregivers.[44],[45],[46] Furthermore, there is less access to oral health care services in the countryside than in the city, supported by the results that oral health service utilization was significantly higher in the urban areas than in rural areas.[47],[48]
There are some limitations to this study. This study used the study areas to define rural and urban locations because it was the only information provided in the included studies. This may not exactly correspond to the definition of rural and urban. Moreover, since most studies in LBC are published in Chinese, it is difficult for non-Chinese readers to access and appraise the information. Despite the limitations, this meta-analysis was the first study that makes a conclusion from the current studies on the caries prevalence of LBC in China. It also gives empirical evidence to show the risk of parental migration on children’s oral health. Importantly, it could provide reference information on oral health problems of the LBC in other countries.
Special oral health care programs are needed to increase the awareness and knowledge of nonparental caregivers on proper oral health care and enhance access to oral health services for LBC, especially in the rural or countryside areas. Moreover, both the government and the community need to get involved in solving this problem. Enhancing local job opportunities to keep the labor force in their hometown may help reduce the number of LBC. Ultimately, since parental migration happens globally and harms children’s health and oral health, the governments and policymakers in every country should focus more on this issue.
| Conclusion | | |
This meta-analysis shows a high prevalence of dental caries among LBC, especially young children aged 3–6 years. Parental migration posed a significant risk for dental caries among children in China (OR = 1.61). The LBC living in the countryside were at a higher risk of dental caries than those living in the city. More studies on the effect of parental migration on dental caries and other oral health issues should be conducted in other countries where parental migration is found to be a social issue. In addition, studies on the reasons for the effect of parental migration on health and oral health problems among these LBC are needed.
Authors’ contributions
Conceptualization: TA, VC, and SZ. Methodology: TA and SL. Data curation: SL and LZ. Formal analysis: SL. Software: SL and LZ. Writing-original draft: SL. Writing-review and editing: TA, VC, SZ, and SL.
Acknowledgement
The authors wish to thank all the researchers who focus on left-behind children.
Financial support and sponsorship
The review was supported by Thailand’s Education Hub for the Southern Region of ASEAN Countries, Prince of Songkla University (No. TEH-AC 042/2018).
Conflicts of interest
There are no conflicts of interest.
Ethical policy and institutional review board statement
This meta-analysis study was conducted from the published articles. It did not require ethics approval.
Patient declaration of consent
Not applicable.
Data availability statement
Further data will be available on request. Kindly contact the corresponding author through email.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2]
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