Robust Confidence Intervals for Meta-Regression with Interaction Effects

TL;DR

This paper reviews and compares robust methods for constructing confidence intervals in mixed-effects meta-regression models with interaction effects, especially in small sample sizes, to improve inference reliability.

Contribution

It introduces and evaluates robust sandwich estimator-based confidence intervals for meta-regression with interactions, providing practical recommendations for researchers.

Findings

Robust confidence intervals generally improve coverage accuracy.

Different estimators vary in interval length and reliability.

Recommendations depend on study conditions and sample size.

Abstract

Meta-analysis is an important statistical technique for synthesizing the results of multiple studies regarding the same or closely related research question. So-called meta-regression extends meta-analysis models by accounting for studylevel covariates. Mixed-effects meta-regression models provide a powerful tool for evidence synthesis, by appropriately accounting for betweem-study heterogeneity. In fact, modelling the study effect in terms of random effects and moderators not only allows to examine the impact of the moderators, but often leads to more accurate estimates of the involved parameters. Nevertheless, due to the often small number of studies on a specific research topic, interactions are often neglected in meta-regression. In this work, we consider the research questions (i) how moderator interactions influence inference in mixed-effects meta-regression models and (ii) whether some inference methods are more reliable than others. Here, we review robust methods for confidence intervals in meta-regression models including interaction effects. These methods are based on the application of robust sandwich estimators for estimating the variance-covariance matrix of the vector of model coefficients. Furthermore, we compare different versions of these robust estimators in an extensive simulation study. We thereby investigate coverage and length of seven different confidence intervals under varying conditions. We conclude with some practical recommendations.