The Care-Full Study: assessing the feasibility of a mixed-method longitudinal data collection approach for unpaid carers of people with multiple long-term conditions

Background Research on unpaid carers often relies on survey and interview data that are cross-sectional or infrequently repeated, providing limited insight into how carers’ experiences and wellbeing evolve over time. Combining frequent longitudinal surveys with regular qualitative check-ins offers a promising mixed-method approach for capturing change, yet there is limited evidence on the feasibility of implementing such data collection strategies over extended periods. Methods As part of the NIHR-funded Care-Full study, we tested the feasibility of a mixed-method longitudinal data collection approach combining fortnightly digital self-report surveys with monthly qualitative check-ins facilitated by trained peer researchers with lived experience of caring. Fifteen unpaid carers were recruited across three sites in England and followed for up to ten months. Feasibility outcomes included recruitment and retention, completion rates, data missingness, engagement with an event-triggered “point of change” mini-survey component, and participant feedback on research participation, accessibility, and data collection approaches. Results Engagement with routine longitudinal data collection was high. No participants withdrew for reasons related to study burden, and completion of fortnightly surveys exceeded 93%, with minimal missing data across key measures of quality of life, health, and caregiving activities. The event-triggered “point of change” survey component proved difficult to implement in practice, with delayed reporting and lower completion rates, and was discontinued after four months. Monthly peer-researcher check-ins were consistently valued by participants, supporting sustained engagement and enabling contextualisation of survey responses over time. Conclusions This feasibility study demonstrates that a mixed-method longitudinal approach combining regular digital surveys with peer-researcher engagement can support sustained data collection with unpaid carers over extended periods. Predictable, low-burden survey schedules were feasible, while regular peer-facilitated qualitative engagement enhanced the interpretability of longitudinal data. The findings provide methodological insights to inform future research seeking to collect longitudinal data on carers’ experiences and wellbeing over time.