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dc.contributor.authorStrugnell, C
dc.contributor.authorOrellana, L
dc.contributor.authorHayward, J
dc.contributor.authorMillar, L
dc.contributor.authorSwinburn, B
dc.contributor.authorAllender, S
dc.date.accessioned2020-12-17T03:24:31Z
dc.date.available2020-12-17T03:24:31Z
dc.date.issued2018-04-01
dc.identifierpii: ijerph15040747
dc.identifier.citationStrugnell, C., Orellana, L., Hayward, J., Millar, L., Swinburn, B. & Allender, S. (2018). Active (Opt-In) Consent Underestimates Mean BMI-z and the Prevalence of Overweight and Obesity Compared to Passive (Opt-Out) Consent. Evidence from the Healthy Together Victoria and Childhood Obesity Study. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH, 15 (4), https://doi.org/10.3390/ijerph15040747.
dc.identifier.issn1661-7827
dc.identifier.urihttp://hdl.handle.net/11343/254873
dc.description.abstractBackground: Tracking population trends in childhood obesity and identifying target areas for prevention requires accurate prevalence data. This study quantified the magnitude of non-participation bias for mean Body Mass Index-z scores and overweight/obesity prevalence associated with low (opt-in) compared to high (opt-out) participation consent methodologies. Methods: Data arose from all Local Government Areas (LGAs) participating in the Healthy Together Victoria Childhood Obesity Study, Australia. Primary schools were randomly selected in 2013 and 2014 and all Grades 4 and 6 students (aged approx. 9-12 years) were invited to participate via opt-in consent (2013) and opt-out consent (2014). For the opt-in wave N = 38 schools (recruitment rate (RR) 24.3%) and N = 856 students participated (RR 36.3%). For the opt-out wave N = 47 schools (RR 32%) and N = 2557 students participated (RR 86.4%). OUTCOMES: differences between opt-in and opt-out sample estimates (bias) for mean BMI-z, prevalence of overweight/obesity and obesity (alone). Standardized bias (Std bias) estimates defined as bias/standard error are reported for BMI-z. Results: The results demonstrate strong evidence of non-participation bias for mean BMI-z overall (Std bias = -4.5, p < 0.0001) and for girls (Std bias = -5.4, p < 0.0001), but not for boys (Std bias = -1.1, p = 0.15). The opt-in strategy underestimated the overall population prevalence of overweight/obesity and obesity by -5.4 and -4.5 percentage points respectively (p < 0.001 for both). Significant underestimation was seen in girls, but not for boys. Conclusions: Opt-in consent underestimated prevalence of childhood obesity, particularly in girls. Prevalence, monitoring and community intervention studies on childhood obesity should move to opt-out consent processes for better scientific outcomes.
dc.languageEnglish
dc.publisherMDPI
dc.rights.urihttps://creativecommons.org/licenses/by/4.0
dc.titleActive (Opt-In) Consent Underestimates Mean BMI-z and the Prevalence of Overweight and Obesity Compared to Passive (Opt-Out) Consent. Evidence from the Healthy Together Victoria and Childhood Obesity Study
dc.typeJournal Article
dc.identifier.doi10.3390/ijerph15040747
melbourne.affiliation.departmentMedicine, Western Health
melbourne.affiliation.facultyMedicine, Dentistry & Health Sciences
melbourne.source.titleInternational Journal of Environmental Research and Public Health
melbourne.source.volume15
melbourne.source.issue4
dc.rights.licenseCC BY
melbourne.elementsid1323976
melbourne.contributor.authorMillar, Lynne
dc.identifier.eissn1660-4601
melbourne.accessrightsOpen Access


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