Consideration of overadjustment bias in guidelines and tools for systematic reviews and meta-analyses of observational studies is long overdue.

This article examines the issue of overadjustment bias in systematic reviews and meta-analyses of observational studies. It emphasizes the need to address biases, such as selection, measurement, and confounding biases, in order to obtain accurate estimates. The authors find that while guidelines and tools for conducting and reporting these reviews often address confounding bias, they rarely consider overadjustment bias. The authors argue that guidelines and tools should explicitly address overadjustment bias to enhance the quality of these reviews. They recommend including overadjustment bias in guidelines and standards, promoting recent tools that address both overadjustment and confounding, and implementing strategies to improve adherence to guidelines. [Extracted from the article]