Public knowledge, preferences and experiences about medical substitute decision-making: a national cross-sectional survey

Objective: To describe the Australian adult public's knowledge and experiences regarding substitute decision-making for medical decisions and their preferences for obtaining information about the substitute decision-maker (SDM) role. Methods: This is a national cross-sectional online survey of the Australian adult public. The survey examined participants' advance care planning (ACP) awareness and experience, SDM experiences and preferences for obtaining more information about SDM, and participant knowledge about SDM. Results: Of 1586 people who opened the survey, 1120 (70.6%) were included in the final sample. 13% (n=142) of participants indicated they had acted as an SDM. A median score of two correct responses out of five showed low to moderate knowledge about the SDM role among all participants, with only 33% reporting awareness of SDM laws existing in Australia. While most (59%) participants ranked a health professional as their preferred source of obtaining information about supporting SDMs, few participants who had been an SDM (n=64, 45%) reported obtaining any support in making medical decisions. The median SDM knowledge scores for people who had discussed ACP (3.0 vs 2.0, U=145222, z=6.910, p<0.001), documented their ACP preferences (3.0 vs 2.0, U=71984, z=4.087, p<0.001) or acted in the SDM role (3.0 vs 2.0, U=56353, z=−3.694, p<0.001) were significantly higher compared with those who had not. Conclusions: The Australian public may have low to moderate knowledge about the SDM role and access only minimal support when making challenging medical decisions.