Shall we count the living or the dead?

TL;DR

This paper analyzes Mindel C. Sheps' 1958 solution to the asymmetry of relative risk, clarifying its scope, stability conditions, and practical implementation for clinical decision-making.

Contribution

It provides causal models to elucidate Sheps' approach, demonstrating its stability under certain conditions and linking it to psychological research and practical methods.

Findings

Sheps' relative risk variant is stable under specific biological conditions.

The approach aligns with psychological theories of causal reasoning.

Practical implementation can use Switch Relative Risk or GRRR.

Abstract

In the 1958 paper "Shall we count the living or the dead?", Mindel C. Sheps proposed a principled solution to the familiar problem of asymmetry of the relative risk. We provide causal models to clarify the scope and limitations of Sheps' line of reasoning, and show that her preferred variant of the relative risk will be stable between patient groups under certain biologically interpretable conditions. Such stability is useful when findings from an intervention study must be generalized to support clinical decisions in patients whose risk profile differs from the participants in the study. We show that Sheps' approach is consistent with a substantial body of psychological and philosophical research on how human reasoners carry causal information from one context to another, and that it can be implemented in practice using van der Laan et al's Switch Relative Risk, or equivalently, using Baker and Jackson's Generalized Relative Risk Reduction (GRRR).