Design and Analysis Considerations for Stepped Wedge Cluster Randomized Trials with Decayed Correlation

by   Fan Li, et al.

A stepped wedge cluster randomized trial is a type of longitudinal cluster design that sequentially switches clusters to intervention over time until all clusters are treated. While the traditional posttest-only parallel design requires adjustment for a single intraclass correlation coefficient, the stepped wedge design allows multiple outcome measurements from the same cluster and so additional correlation parameters are necessary to characterize the within-cluster dependency structure. Although a number of studies have differentiated between the concepts of within-period and inter-period correlations, few studies have allowed the inter-period correlation to decay over time. In this article, we consider the proportional decay correlation structure for a cohort stepped wedge design, and provide a matrix-adjusted quasi-least squares (MAQLS) approach to accurately estimate the correlation parameters along with the intervention effect. We further develop a corresponding sample size procedure accounting for the correlation decay, and numerically validate it for continuous outcomes in a simulation study. We show that the empirical power agrees well with the prediction even with a small number of clusters, when data are analyzed with MAQLS concurrently with a suitable bias-corrected sandwich variance. Two trial examples are provided to illustrate the new sample size procedure.


page 1

page 2

page 3

page 4


Power considerations for generalized estimating equations analyses of four-level cluster randomized trials

In this article, we develop methods for sample size and power calculatio...

Optimal Study Designs for Cluster Randomised Trials: An Overview of Methods and Results

There are multiple cluster randomised trial designs that vary in when th...

Efficient design of geographically-defined clusters with spatial autocorrelation

Clusters form the basis of a number of research study designs including ...

Marginal modeling of cluster-period means and intraclass correlations in stepped wedge designs with binary outcomes

Stepped wedge cluster randomized trials (SW-CRTs) with binary outcomes a...

Improving sandwich variance estimation for marginal Cox analysis of cluster randomized trials

Cluster randomized trials (CRTs) frequently recruit a small number of cl...

Please sign up or login with your details

Forgot password? Click here to reset