Understanding the trajectory of frailty across the life course.

Background Frailty is a useful construct to identify future adverse risks in older people, across a range of settings. Yet it is not clear how it might usefully be applied in people aged 18-64. This work plans to use two established approaches to measuring frailty at scale and assess their possible utility in younger people. Aims and Objectives We aim to determine if i) the deficit accumulation model of frailty and ii) the Hospital Frailty Risk Score are related to outcomes in people aged 18-64 using cohort and routinely collected data, respectively. Objectives: Construct longitudinal Frailty Indices (FIs) from prospective follow-up assessments in three UK national birth cohort studies (data collection since 1946, 1958 and 1970) to describe deficit accumulation in individuals aged 18 to 64. Co-ordinated analyses across the cohorts will lead to the first population-based estimates of frailty trajectories over the whole adult life course. Use English Hospital Episode Statistics (HES) to (i) generate Hospital Frailty Risk Scores (HFRSs) for all patients aged 18-64 from 2013 to 2019 and (ii) for hospitalised birth cohort participants through linked HES data. Link the frailty measures ascertained in cohort and electronic health data to existing outcomes, including quality of life, disability, physical and cognitive function, psychological distress, mortality, hospital use and costs. Examine the relationships between FI scores and HFRS and key outcomes in subgroups of younger individuals with selected long-term conditions. Describe how socioeconomic position, psychological, lifestyle and behavioural factors in childhood and mid-life contribute to levels and trajectories of frailty. Engage with lay and professional stakeholders to discuss emerging findings on frailty across the life course, associated outcomes, and relative importance at different ages. Methods We will derive longitudinal Frailty Index (FI) scores in the three oldest national British birth cohorts, defining intra-individual, inter-individual and inter-generational variability across the adult lifespan (ages 18 to 64). By describing population frailty trajectories in younger adults and investigating how they relate to outcomes, we can also examine these associations in individuals with long-term conditions with onset at younger ages. Using prospectively ascertained data, we will also identify the determinants of frailty that arise at all stages of the life course. In parallel, we will calculate HFRSs for those ages 18-64 hospitalised between 2013-2019 across all English hospitals to describe the distribution of frailty risk in this cohort, and associations with length of stay and mortality. Using linked NHS data from the birth cohorts, we will describe the relationship between FI scores and the HFRS. We will engage lay and professional stakeholders throughout the research process to help shape the research, advise on interpretation and any implications for policy and practice. Timelines for delivery The projected start date is January 2022, with a study duration of 18 months. Anticipated Impact and Dissemination We will generate empirical evidence, influence policy by involving a range of lay and professional national stakeholders (including the national director for health inequalities) and provide implementation tools to inform system-wide implementation.