Unbalanced Baseline in School-based Interventions to Prevent Obesity: Adjustment Can Lead to Bias - a Systematic Review

Overview

Journal Obes Facts

Publisher Karger

Specialty Endocrinology

Date 2014 Jul 5

PMID 24993013

Citations 4

Authors

Rosely Sichieri

Diana Barbosa Cunha

Affiliations

Soon will be listed here.

Abstract

Background/aims: Cluster designs favor unbalanced baseline measures. The aim of the present study was to determine the frequency of unbalanced baseline BMI on school-based randomized controlled trials (RCT) aimed at obesity reduction and to evaluate the analysis strategies. We hypothesized that the adjustment of unbalanced baseline measures may explain the great discrepancy among studies.

Methods: The source of data was the Medline database content from January 1995 until May 2012. Our search strategy combined key words related to school-based interventions with such related to weight and was not limited by language. The participants' ages were restricted to 6-18 years.

Results: We identified 146 school-based studies on obesity prevention (or overweight or excessive weight change). Of the 146 studies, 36 were retained for the analysis after excluding reviews, feasibility studies, other outcomes, and repeated publications. 13 (35%) of the reviewed studies had statistically significant (p < 0.05) unbalanced measures of BMI at baseline. 11 studies with BMI balanced at baseline adjusted for the baseline BMI, whereas no baseline adjustment was applied to the 5 unbalanced studies.

Conclusion: Adjustment for the baseline BMI is frequently done in cluster randomized studies, and there is no standardization for this procedure. Thus, procedures that disentangle the effects of group, time and changes in time, such as mixed effects models, should be used as standard methods in school-based studies on the prevention of weight gain.

Citing Articles

PAAPPAS community trial protocol: a randomized study of obesity prevention for adolescents combining school with household intervention.

Sgambato M, Cunha D, Henriques V, Estima C, Souza B, Pereira R BMC Public Health. 2016; 16(1):809.

PMID: 27534742 PMC: 4989464. DOI: 10.1186/s12889-016-3473-3.

Concerning Sichieri R, Cunha DB: Obes Facts 2014;7:221–232. The Assertion that Controlling for Baseline (Pre-Randomization) Covariates in Randomized Controlled Trials Leads to Bias is False.

Li P, Brown A, Dawson J, Kaiser K, Bohan Brown M, Keith S Obes Facts. 2015; 8(2):127-9.

PMID: 25871982 PMC: 4494880. DOI: 10.1159/000381434.

Authors’ response to Li et al. Obes Facts 2015;8:DOI: 10.159/000381434.

Sichieri R, Cunha D Obes Facts. 2015; 8(2):130-1.

PMID: 25870949 PMC: 5644869. DOI: 10.1159/000381576.

Quality Management in Scientific Publishing--the Importance to Critically Scrutinize Scientific Work.

Hauner H Obes Facts. 2015; 8(2):125-6.

PMID: 25832728 PMC: 5644844. DOI: 10.1159/000381481.

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