Background The UK End of Life Care (EoLC) Strategy proposed that all people should identify preferences for end of life care.

Aim To explore whether family carers of a person with dementia (PWD) can accurately predict their preferences for EoLC and what factors influence this.

Methods This mixed methods study began with nominal groups (NG) to explore if PWD and carers could generate and prioritise preferences for EoLC and if carers influenced the PWD’s choices. Phase 2 involved 60 dyad interviews using a modified Life Support Preferences Questionnaire to assess whether carers could predict the PWD’s preferences for treatment in three health states. Influence of carer burden, distress, and relationship quality were measured. Nested qualitative interviews added personal contexts to decision making.

Results In NGs, PWD struggled to conceive of their future selves and think about preferences for EoLC. Carers’ views were influenced by their personal experiences and negative media coverage and they tended to override the PWD’s views. In interviews, carers predicted the PWD’s preferences in the here-and-now but were inaccurate in future hypothetical health states. Both showed uncertainty about EoLC treatment choices. Relationship quality, carer distress and burden did not influence accuracy of prediction. In qualitative interviews, while dyads claimed to have a shared decision making approach, joint healthcare decision making had largely been untested.

Conclusion Families affected by dementia require practical and emotional support at the outset to accommodate changes in patterns of decision making, prepare for changes ahead and ensure that PWD’s preferences are upheld.