Strategies for enhancing the representation of women in clinical trials: an evidence map

Equitable sex- and gender-based representation in clinical trials is an essential step to ensuring evidence-based care for women. While multi-institutional actions have led to significant improvements in the inclusion of women in trials, inequity persists in areas like sex-neutral cancers and cardiovascular disease. We sought to identify strategies described or evaluated to boost the inclusion of women in clinical trials.

We used evidence mapping methodology to examine the breadth of relevant literature. We developed an a priori protocol and followed reporting guidance from the Preferred Reporting Items for Systematic Reviews and Meta-Analysis where applicable. We searched MEDLINE^® (via PubMed) and EMBASE (via Elsevier) databases from inception through April 4, 2023, and used standardized procedures incorporating duplication and data verification. We included articles that described strategies to improve the recruitment and retention of women in clinical trials.

We identified 122 articles describing recruitment and retention strategies for 136 trials (377,595 women). Only one article distinguished between the sex and gender identity of participants, and none defined their use of the terms such as “women” or “female”. The majority of articles (95%) described recruitment for only women, and 64% were conducted in the USA. Ninety-two articles (75%) described strategies in the context of sex-specific conditions (e.g., gynecologic diagnosis). The majority of included articles evaluated a behavioral intervention (52%), with 23% evaluating pharmacologic interventions and 4% invasive interventions. The most common trial phase for reported strategies was during outreach to potential participants (116 articles), followed by intervention delivery (76), enrollment (40), outcomes assessment (21), analysis and interpretation (3), and dissemination (4). We describe specific types of strategies within each of these phases.

Most of the existing literature describing strategies to improve the inclusion of women draws from trials for sex-specific conditions and is largely related to outreach to potential participants. There is little information about how and if studies have attempted to proportionally increase the inclusion of women in trials with both men and women or those focused on invasive and pharmacologic interventions. Future work in this area should focus on how to increase the participation of women in mixed-sex studies and on those areas with remaining inequities in trial participation.