Document Detail


Accelerated longitudinal designs: An overview of modelling, power, costs and handling missing data.
MedLine Citation:
PMID:  25147228     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Longitudinal studies are often used to investigate age-related developmental change. Whereas a single cohort design takes a group of individuals at the same initial age and follows them over time, an accelerated longitudinal design takes multiple single cohorts, each one starting at a different age. The main advantage of an accelerated longitudinal design is its ability to span the age range of interest in a shorter period of time than would be possible with a single cohort longitudinal design. This paper considers design issues for accelerated longitudinal studies. A linear mixed effect model is considered to describe the responses over age with random effects for intercept and slope parameters. Random and fixed cohort effects are used to cope with the potential bias accelerated longitudinal designs have due to multiple cohorts. The impact of other factors such as costs and the impact of dropouts on the power of testing or the precision of estimating parameters are examined. As duration-related costs increase relative to recruitment costs the best designs shift towards shorter duration and eventually cross-sectional design being best. For designs with the same duration but differing interval between measurements, we found there was a cutoff point for measurement costs relative to recruitment costs relating to frequency of measurements. Under our model of 30% dropout there was a maximum power loss of 7%.
Authors:
Sally Galbraith; Jack Bowden; Adrian Mander
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2014-8-20
Journal Detail:
Title:  Statistical methods in medical research     Volume:  -     ISSN:  1477-0334     ISO Abbreviation:  Stat Methods Med Res     Publication Date:  2014 Aug 
Date Detail:
Created Date:  2014-8-22     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9212457     Medline TA:  Stat Methods Med Res     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
© The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
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