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Original research
Persistent poverty and child dental caries: time-varying exposure analysis
  1. Yusuke Matsuyama1,2,
  2. Aya Isumi3,
  3. Satomi Doi3,
  4. Takeo Fujiwara1
  1. 1 Department of Global Health Promotion, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
  2. 2 Department of Oral Health Promotion, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
  3. 3 Department of Health Policy, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan
  1. Correspondence to Professor Takeo Fujiwara, Department of Global Health Promotion, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510, Japan; fujiwara.hlth{at}tmd.ac.jp

Abstract

Background This study investigated the cumulative impact of persistent poverty on dental caries among elementary schoolchildren in Japan.

Methods Data were derived from four-wave longitudinal data of children in all public elementary schools in Adachi City, Tokyo, Japan, from 2015 to 2020 (n=4291, response rate: 80.1%–83.8%). Poverty status, defined as annual household income <JPY3 million, material deprivation or payment difficulties for lifeline utilities, was assessed by caregiver questionnaires when the children were in the first, second, fourth and sixth grades. School dentists assessed dental caries. We estimated the difference in the number of primary and permanent teeth with incidences of dental caries from second to sixth grade by persistent poverty and never having experienced poverty. Targeted maximum likelihood estimation was used to consider baseline and time-varying confounders.

Results Children with persistent poverty experienced more dental caries (mean: 3.81, SD: 3.73) than children who had never experienced poverty (mean: 2.39, SD: 3.27). After controlling for confounders, being in persistent poverty was significantly associated with having more dental caries than never being in poverty (mean difference: 1.54, 95% CI 0.60, 2.48). The magnitude of the association was greater than that of poverty assessed at first grade only (mean difference: 0.75, 95% CI 0.35, 1.16) or experience of poverty at any of the four waves (mean difference: 0.69, 95% CI 0.39, 0.99).

Conclusion The cumulative impact of persistent poverty could be larger than the poverty assessed at a single time point.

  • EPIDEMIOLOGY
  • BIOSTATISTICS
  • DENTISTRY

Data availability statement

No data are available. Deidentified individual participant data will not be made available.

http://dx.doi.org/10.1136/jech-2022-220073

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    Data availability statement

    No data are available. Deidentified individual participant data will not be made available.

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    Footnotes

    • Contributors YM contributed to conception and design, analysis and interpretation, and manuscript drafting. AI and SD contributed to data acquisition, project administration and interpretation, and critically revised the manuscript. TF contributed to conception and design, data acquisition, funding acquisition, project administration and interpretation, and critically revised manuscript. All authors granted final approval and agreed to be accountable for all aspects of the work. TF is the guarantor of this work.

    • Funding This study was supported by a Health Labor Sciences Research Grant, Comprehensive Research on Lifestyle Disease from the Japanese Ministry of Health, Labor and Welfare (H27-Jyunkankito-ippan-002), Research of Policy Planning and Evaluation from the Japanese Ministry of Health, Labor and Welfare (H29-Seisaku-Shitei-004), Innovative Research Program on Suicide Countermeasures, and Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (JSPS KAKENHI grant numbers 16H03276, 16K21669, 17J05974, 17K13245, 19K19310, 19K14029, 19K19309, 19K20109, 19K14172, 19J01614, 19H04879, 20K13945, 21H04848 and 21K18294), St Luke’s Life Science Institute Grants, the Japan Health Foundation Grants, and Research-Aid (Designated Theme), Meiji Yasuda Life Foundation of Health and Welfare.

    • Competing interests None declared.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.