Abstract Number: Esoc2026a691 Trial Design and Stroke Phase as Determinants of Sex Differences in Non-Participation in Stroke Trials

Abstract Background and aims Women remain underrepresented in stroke clinical trials despite a higher lifetime risk of stroke and poorer post-stroke outcomes. Although sex differences in trial participation have been reported, the influence of trial design and the timing of enrolment within the stroke pathway on sex-specific non-participation remains unclear. To examine whether trial design (Drug RCTs,non- drug RCTs, and observational trials) and stroke phase (hyperacute, acute, sub-acute, and chronic) are associated with sex differences in non-participation in stroke clinical trials. Methods Retrospective observational study of adult stroke patients aged ≥18 years and older admitted to The Alfred Health Comprehensive Stroke Centre between February 2019 and March 2025. Results Among 494 eligible patients (235 females, 259 males), 340 (68.8%) consented, with lower consent rates among females than males (57.0% vs 79.5%, p 0.001). Declines were higher among females than males (26.8% vs 17.8%). Non-participation varied by trial design, with the largest sex differences observed in drug RCTs, where decline rates were higher among females than males (28.1% vs 18.4%). Declines were also more frequent among females in non-drug RCTs (23.9% vs 17%) and observational trials (33.3% vs 22.2%). Across stroke phases, non-participation was most frequent in acute and chronic trials, with higher female decline rates in the chronic phase (29.3% vs 17.3%). Conclusions Sex differences in non-participation varied by trial design and stroke phase, suggesting that disparities in stroke trial participation are influenced by structural and temporal features of trial design rather than solely by patient preference. Conflict of interest Pamela Galindo: Nothing to disclose; Mycah Astrera-Sgro: Nothing to dislcose; Professor Geoffrey Cloud: Nothing to disclose; Dr Vimal Stanisalus: Nothing to disclose