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Comparative Study
. 2025 Jan 10:69:1607669.
doi: 10.3389/ijph.2024.1607669. eCollection 2024.

Methodological Approaches to Comparative Trend Analyses: The Case of Adolescent Toothbrushing

Torbjørn Torsheim  1 , Frank J Elgar  2 , Alina Cosma  3   4 , Caroline Residori  5 , Oddrun Samdal  6 , Christina Schnohr  7   8
Affiliations
Comparative Study

Methodological Approaches to Comparative Trend Analyses: The Case of Adolescent Toothbrushing

Torbjørn Torsheim et al. Int J Public Health. .

Abstract

Objectives: Research questions about how and why health trends differ between populations require decisions about data analytic procedure. The objective was to document and compare the information returned from stratified, fixed effect and random effect approaches to data modelling for two prototypical descriptive research questions about comparative trends in toothbrushing.

Methods: Data included five cycles of the Health Behaviour in School-aged Children 2006 to 2022, which provided a sample of 980192 11- to 15- year olds from 35 countries. Using logistic regression models and generalized linear mixed models, toothbrushing daily was regressed on time, following the three approaches to analysis of trends.

Results: The stratified approach suggested a positive but non-linear trend in toothbrushing from 2006 to 2022 in most countries but provided no statistical inference on the variation. The fixed effect and the random effect approach converged on a positive but flattening overall trend, with a statistically significant country variation in trends.

Conclusion: Only the fixed effect approach and the random effects approach provided clear answers to the research question. Additional methodological considerations for making an informed choice of analytical approach are discussed.

Keywords: HBSC study; comparative analyses; methodological research; toothbrushing; trend analysis.

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Conflict of interest statement

The authors declare that they do not have any conflicts of interest.

Figures

FIGURE 1
FIGURE 1
Predicted toothbrushing by time per pattern of trend components, stratified approach. (A) Countries with no trend; (B) Countries with linear trend; (C) Countries with linear and quadratic components; (D) Countries with Linear, quadratic and cubic trend components; (E) Countries with linear and cubic trend components; (F) Countries with quadratic and cubic trend components (Data from Health behaviour in school-aged children 2006–2022).
FIGURE 2
FIGURE 2
Predicted toothbrushing by time. (A, B) Show predictions from fixed effect model, (C, D) shows predictions from random effect model. (A, C) give predictions per country or region, one line per country/region. (B, D) give mean overall prediction, with confidence intervals (Data from Health behaviour in school-aged children 2006–2022).
See this image and copyright information in PMC

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