Process evaluation of a New psychosocial goal-setting and manualised support intervention for Independence in Dementia (NIDUS-Family)

We report a mixed-methods process evaluation embedded within a randomised controlled trial. We aimed to test and refine a theory of change model hypothesising key causal assumptions to understand how the New Interventions for Independence in Dementia Study (NIDUS)-Family (a manualised, multimodal psychosocial intervention), was effective relative to usual care, on the primary outcome of Goal Attainment Scaling (GAS) over 1 year.

In 2021-2022, intervention-arm dyads completed an acceptability questionnaire developed to test causal assumptions. We conducted qualitative interviews with dyads and intervention facilitators, purposively selected for diverse follow-up GAS scores. We collected observational data from intervention session recordings. We thematically analysed data, then integrated qualitative and quantitative data.

174/204 (85.3%) dyads allocated to NIDUS-Family, fully completed it, 18 partially completed, while 12 received no intervention. We interviewed 27/192 (14%) of dyads receiving any sessions, and 9/10 facilitators; and observed 12 sessions. 47/192 (24.5%) of carers completed the acceptability questionnaire. We identified four themes: (A) 'Someone to talk to helps dyads feel supported'; (B) 'NIDUS-Family helps carers change their perspective'; (C) 'Personalisation helps people living with dementia maintain their identity' and (D) 'Small steps help dyads move forward'.

Key causal pathway mechanisms were: a respectful, trusting and impartial relationship with the facilitator: supporting the development of meaningful goals and support to find manageable solutions. Core implementation factors were delivery of the modules from a consistent facilitator across regular sessions. Core contextual factors influencing these mechanisms were dyadic participation and understanding of abilities.