Background. Over the last hundred years, the increase in longevity, first regarded as one of the greatest successes of humankind, became perceived as a global challenge with substantial and changing implications for societies, economies, and health care systems. To respond to this challenge, a first step is to understand the change in health and social care needs in older age to inform policy and practice. The Cambridge City over-75s Cohort (CC75C) study (1985-2015), one of the largest and longest-running population-based studies of the oldest old (75+ years at recruitment), provides a rare opportunity to investigate the patterns of change in physical, mental, and social health profiles and health and social services use in older age.

Objectives. The project aimed to (1) summarise the evidence on the link between social wellbeing and outcomes of interest (mortality and health/ social services use), (2) derive a measure of social wellbeing and describe its longitudinal change, (3) describe the change in health profiles and health/ social services use over the 10 waves of follow-up, (4) determine the longitudinal associations between social wellbeing and outcomes, and finally (5) provide an overview and evaluation of health service use models with respect to the results.

Methods. A literature review and a systematic review of reviews were carried out to summarise the evidence on social wellbeing in older age with respect to mortality and health/ social services use. The derivation of a social wellbeing index (SWI) was based on a standardisation method using data pertaining to four social dimensions: relationships, network, support, and participation. Longitudinal descriptive and inferential analyses were conducted. The latter were based on marginal models (generalised estimating equations) and time-to-event-models (Cox regression and competing risks analyses) depending on study outcomes. Missing data were investigated, described, and adjusted for, using different methods including multiple imputation and inverse probability weighting.

Results. The review of the literature showed that lower social support, having no spouse, or living alone were associated with higher risk of re-hospitalisation and emergency department visit, with some variation in patterns. Health service use models ranged from broad (for example, the Andersen behavioural model) to specific (for example, a post-hip fracture rehabilitative care model) and focused on healthcare services rather than social care services or both. The analyses revealed that while care needs and health/ social services use increased, social wellbeing decreased as the cohort aged. Furthermore, a higher SWI was significantly associated with a decreased risk of mortality, use of social care services, and stay at a residential care home, and with a more recent last GP visit.

Conclusion. This body of work provides (1) a higher-level synthesis of the evidence on social wellbeing in older age, (2) a first longitudinal social wellbeing index based on common social dimensions with details on its conceptualisation and derivation for replication and benchmarking purposes, (3) empirical evidence on the change in patterns of care needs and health/ social services use in older age using a rare longitudinal study, (4) robust quantitative longitudinal evidence on the protective effect of social wellbeing against mortality risk and health/ social services use, and finally (5) an overview and critique of health service use models suggesting the incorporation of social health predictors and social care service use outcomes. Implications for research, practice, and policy are discussed.