Background Communicating wishes regarding future research participation in the event of incapacity may help proxies make enrolment decisions that are more consistent with these wishes.

Aim To test an advance planning intervention designed to (1) motivate older adults to document their wishes regarding future research participation and (2) guide proxies in making hypothetical research decisions.

Methods Randomised controlled trial involving 235 older adults and proxies. The experimental intervention included a group information session on advance directives and two encounters with a facilitator who helped older adults communicate their wishes. Control participants attended three workshops on healthy behaviours. Hypothetical studies were used at baseline and twice post-intervention to elicit preferences and assess proxies’ prediction ability.

Results At trial completion, 80% of experimental participants had documented their preferences. Half indicated a willingness to participate in research should they be solicited after losing capacity. At baseline, percentages of agreement on willingness to enrol in the hypothetical studies ranged from 93 (95% CI from 90 to 96) for a blood draw in the older adult’s current health state to 52 (95% CI from 45 to 58) for a dementia drug trial. Agreement changed over time (p < 0.001), but the group and group-by-time interaction were non-significant (p = 0.734 and 0.141, respectively).

Discussion/conclusion The intervention motivated older adults to record their preferences regarding future research involvement. It did not improve proxies’ ability to predict their willingness to enrol in hypothetical studies. It remains to be seen whether recording preferences would facilitate substitute decision-making in actual research situations.