dc.contributor.author | Zheng, H | |
dc.contributor.author | Kimber, A | |
dc.contributor.author | Goodwin, V | |
dc.contributor.author | Pickering, R | |
dc.date.accessioned | 2017-09-11T07:54:04Z | |
dc.date.issued | 2017-10-25 | |
dc.description.abstract | A common design for a falls prevention trial is to assess falling at baseline, randomize participants into
an intervention or control group, and ask them to record the number of falls they experience during a
follow-up period of time. This paper addresses how best to include the baseline count in the analysis of
the follow-up count of falls in Negative Binomial (NB) regression. We examine the performance of
various approaches in simulated datasets where both counts are generated from a mixed Poisson
distribution with shared random subject effect. Including the baseline count after log-transformation as a
regressor in NB regression (NB-logged) or as an offset (NB-offset) resulted in greater power than
including the untransformed baseline count (NB-unlogged). Cook and Wei's Conditional Negative
Binomial (CNB) model replicates the underlying process generating the data. In our motivating dataset, a
statistically significant intervention effect resulted from the NB-logged, NB-offset and CNB models, but
not from NB-unlogged, and large, outlying baseline counts were overly influential in NB-unlogged but
not in NB-logged. We conclude that there is little to lose by including the log-transformed baseline count
in standard NB regression compared to CNB for moderate to larger sized datasets. | en_GB |
dc.description.sponsorship | Funding Information: National Institute for Health Research, Grant no. RDA/02/06/41; Care South West Peninsula | en_GB |
dc.identifier.citation | Published online 25 October 2017 | en_GB |
dc.identifier.doi | 10.1002/bimj.201700103 | |
dc.identifier.uri | http://hdl.handle.net/10871/29274 | |
dc.language.iso | en | en_GB |
dc.publisher | Wiley-VCH Verlag | en_GB |
dc.rights.embargoreason | Publisher policy | en_GB |
dc.rights | © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim | |
dc.subject | Baseline counts | en_GB |
dc.subject | Negative binomial | en_GB |
dc.subject | Regression | en_GB |
dc.subject | Simulations | en_GB |
dc.title | A comparison of different ways of including baseline counts in negative binomial models for data from falls prevention trials | en_GB |
dc.type | Article | en_GB |
dc.identifier.issn | 0323-3847 | |
dc.description | This is the author accepted manuscript. The final version is available from Wiley-VCH Verlag via the DOI in this record. | en_GB |
dc.identifier.journal | Biometrical Journal | en_GB |