Background With population ageing accelerating worldwide, long-term care needs are rising, and family caregivers have become an essential yet often under-recognised component of care systems. Older family caregivers are particularly susceptible to frailty because they shoulder substantial caregiving responsibilities while simultaneously experiencing their own age-related decline in health and physiological reserve. Frailty is a clinically important state of heightened vulnerability to stressors and is associated with serious adverse outcomes, including disability, hospitalisation, and mortality. In family caregivers, frailty may compromise not only health and quality of life, but also their capacity to sustain caregiving, with wider implications for the sustainability of family-based long-term care.

Research gaps A scoping review conducted by this team indicated that middle-aged and older family caregivers, particularly spousal caregivers, are vulnerable to frailty, with caregiving-related, sociodemographic, physical, psychological, and social factors contributing to this condition. However, existing evidence remains fragmented. Caregiver-specific prognostic tools for estimating future frailty risk are lacking, and risk-stratified interventions among family caregivers are sparse.

Aim This study aims to develop and validate an incident frailty risk prediction model for middle-aged and older spousal caregivers, identify modifiable risk factors, as well as develop and preliminarily evaluate a risk-stratified, social robot-assisted intervention to reduce the risk of frailty.

Methods This study comprises four phases. Phase 1 is a completed scoping review that mapped evidence on frailty among middle-aged and older family caregivers. Phase 2 will use longitudinal data from the China Health and Retirement Longitudinal Study (CHARLS) to develop and validate an incident frailty risk prediction model for middle-aged and older spousal caregivers and to construct an online risk calculator. Phase 3 will develop social robot-assisted intervention based on the Capability, Opportunity, Motivation-Behavior (COM-B) model. Phase 4 will assess the feasibility, acceptability, and examine preliminary effects of the intervention.

Expected outcomes This study is expected to provide a caregiver-specific tool for early frailty risk identification and risk stratification among middle-aged and older spousal caregivers. It will also generate a theoretically guided, risk-stratified social robot-assisted intervention targeting modifiable risk factors for frailty and provide evidence on its feasibility and acceptability, as well as preliminary effects. The findings will inform a future definitive large-scale trial and community-based caregiver support services.