Comparing meta-analysis and linear mixed model-based approaches for the analysis of continuous outcomes from batched stepped wedge trials

When batched stepped wedge trials include a small number of batches (two and five batches), linear mixed models provide unbiased estimates of treatment effects when correctly specified, but exhibit under-coverage of confidence intervals when treatment effect heterogeneity is present. Random-effects meta-analysis approaches provide unbiased estimates and nominal confidence interval coverage whether or not period or treatment effects vary across batches, but can yield excessively wide confidence intervals. When batched stepped wedge trials include small numbers of batches, we recommend the use of random-effects meta-analysis approaches for the analysis of continuous outcomes.