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. 2014;7(4):221-32.
doi: 10.1159/000363438. Epub 2014 Jun 28.

Unbalanced baseline in school-based interventions to prevent obesity: adjustment can lead to bias - a systematic review

Rosely Sichieri  1 , Diana Barbosa Cunha
Affiliations

Unbalanced baseline in school-based interventions to prevent obesity: adjustment can lead to bias - a systematic review

Rosely Sichieri et al. Obes Facts. 2014.

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.

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Figures

Fig. 1
Fig. 1
Flowchart of the selection of the studies.
See this image and copyright information in PMC

Comment in

References

    1. Davis SM, Going SB, Helitzer DL, Teufel NI, Snyder P, Gittelsohn J, Metcalfe L, Arviso V, Evans M, Smyth M, Brice R, Altaha J. Pathways: a culturally appropriate obesity-prevention program for American Indian schoolchildren. Am J Clin Nutr. 1999;69((4 suppl)):796S–802S. - PMC - PubMed
    1. Gortmaker SL, Peterson K, Wiecha J, Sobol AM, Dixit S, Fox MK, Laird N. Reducing obesity via a school-based interdisciplinary intervention among youth: Planet Health. Arch Pediatr Adolesc Med. 1999;153:409–418. - PubMed
    1. Khambalia AZ, Dickinson S, Hardy LL, Gill T, Baur LA. A synthesis of existing systematic reviews and meta-analyses of school-based behavioural interventions for controlling and preventing obesity. Obes Rev. 2012;13:214–233. - PubMed
    1. Doak C, Heitmann BL, Summerbell C, Lissner L. Prevention of childhood obesity – what type of evidence should we consider relevant? Obes Rev. 2009;10:350–356. - PubMed
    1. Cologne JB. Re: ‘when is baseline adjustment useful in analyses of change? An example with education and cognitive change’. Am J Epidemiol. 2006;164:1138–1139. author reply 1139-1140. - PubMed

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