Global Inequalities in Clinical Trials Participation

TL;DR

This study reveals that global inequalities in clinical trial participation are primarily driven by country-level factors rather than disease burden, highlighting the need for broad investments in research capacity and infrastructure.

Contribution

It provides a comprehensive analysis showing that country-specific factors dominate participation disparities across multiple diseases, challenging disease-focused intervention strategies.

Findings

Participation is highly concentrated in a few countries.

Country factors explain over 90% of participation variation.

Disease-specific effects have minimal impact on overall inequality.

Abstract

Clinical trials shape medical evidence and determine who gains access to experimental therapies. Whether participation in these trials reflects the global burden of disease remains unclear. Here we analyze participation inequality across more than 62,000 randomized controlled trials spanning 16 major disease categories from 2000 to 2024. Linking 36.8 million trial participants to country-level disease burden, we show that global inequality in clinical trials participation is overwhelmingly shaped by country rather than disease burden. Country-level factors explain over 90% of variation in participation, whereas disease-specific effects contribute only marginally. Removing entire disease categories-including those traditionally considered underfunded-has little effect on overall inequality. Instead, participation is highly concentrated geographically, with a small group of countries enrolling a disproportionate share of participants across nearly all diseases. These patterns have persisted despite decades of disease-targeted funding and increasing alignment between research attention and disease burden within diseases. Our findings indicate that disease-vertical strategies alone cannot correct participation inequality. Reducing global inequities in clinical research requires horizontal investments in research capacity, health infrastructure, and governance that operate across disease domains.