Linear mixed models to handle missing at random data in trial-based economic evaluations

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Trial-based cost-effectiveness analyses (CEAs) are an important source of evidence in the assessment of health interventions. In these studies, cost and effectiveness outcomes are commonly measured at multiple time points, but some observations may be missing. Restricting the analysis to the participants with complete data can lead to biased and inefficient estimates. Methods, such as multiple imputation, have been recommended as they make better use of the data available and are valid under less restrictive Missing At Random (MAR) assumption. Linear mixed effects models (LMMs) offer a simple alternative to handle missing data under MAR without requiring imputations, and have not been very well explored in the CEA context. In this manuscript, we aim to familiarize readers with LMMs and demonstrate their implementation in CEA. We illustrate the approach on a randomized trial of antidepressants, and provide the implementation code in R and Stata. We hope that the more familiar statistical framework associated with LMMs, compared to other missing data approaches, will encourage their implementation and move practitioners away from inadequate methods.

Keywords

  • cost-effectiveness analysis, missing data, mixed-effects, Randomised trial, repeated measures
Original languageEnglish
Pages (from-to)1276-1287
Number of pages12
JournalHealth Economics
Volume31
Issue number6
Early online date2 Apr 2022
DOIs
Publication statusPublished - Jun 2022

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