Optimal combination of number of participants and number of repeated measurements in longitudinal studies with time-varying exposure
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- dc.contributor.author Barrera Gómez, Jose
- dc.contributor.author Spiegelman, Donna
- dc.contributor.author Basagaña Flores, Xavier
- dc.date.accessioned 2019-02-07T07:55:37Z
- dc.date.available 2019-02-07T07:55:37Z
- dc.date.issued 2013
- dc.description.abstract In the context of observational longitudinal studies, we explored the values of the number of participants and the number of repeated measurements that maximize the power to detect the hypothesized effect, given the total cost of the study. We considered two different models, one that assumes a transient effect of exposure and one that assumes a cumulative effect. Results were derived for a continuous response variable, whose covariance structure was assumed to be damped exponential, and a binary time-varying exposure. Under certain assumptions, we derived simple formulas for the approximate solution to the problem in the particular case in which the response covariance structure is assumed to be compound symmetry. Results showed the importance of the exposure intraclass correlation in determining the optimal combination of the number of participants and the number of repeated measurements, and therefore the optimized power. Thus, incorrectly assuming a time-invariant exposure leads to inefficient designs. We also analyzed the sensitivity of results to dropout, mis-specification of the response correlation structure, allowing a time-varying exposure prevalence and potential confounding impact. We illustrated some of these results in a real study. In addition, we provide software to perform all the calculations required to explore the combination of the number of participants and the number of repeated measurements.
- dc.description.sponsorship Research was supported, in part, by National Institutes of Health (grant number CA06516)
- dc.format.mimetype application/pdf
- dc.identifier.citation Barrera-Gómez J, Spiegelman D, Basagaña X. Optimal combination of number of participants and number of repeated measurements in longitudinal studies with time-varying exposure. Stat Med. 2013 Nov 30;32(27):4748-62. DOI: 10.1002/sim.5870
- dc.identifier.doi http://dx.doi.org/10.1002/sim.5870
- dc.identifier.issn 0277-6715
- dc.identifier.uri http://hdl.handle.net/10230/36520
- dc.language.iso eng
- dc.publisher Wiley-VCH Verlag
- dc.relation.ispartof Statistics in Medicine. 2013 Nov 30;32(27):4748-62
- dc.rights © 2013 John Wiley & Sons, Ltd. Optimal combination of number of participants and number of repeated measurements in longitudinal studies with time-varying exposure, Jose Barrera-Gómez; Donna Spiegelman; Xavier Basagaña, Statistics in Medicine, 32 (27)
- dc.rights.accessRights info:eu-repo/semantics/openAccess
- dc.subject.other Mobilitat obligada per treball
- dc.subject.other Memòria immediata
- dc.subject.other Aire -- Contaminació
- dc.subject.other Infants
- dc.title Optimal combination of number of participants and number of repeated measurements in longitudinal studies with time-varying exposure
- dc.type info:eu-repo/semantics/article
- dc.type.version info:eu-repo/semantics/acceptedVersion