Does change in area-level deprivation, change health outcomes? A latent class growth analysis of population data.

While deprivation is consistently predictive of health, it is typically studied at one point in time in relation to health outcomes. Emerging research indicates that trajectories of social mobility may be a more powerful predictor of health than point-in-time analyses. This study seeks to identify distinct area-level deprivation trajectories within the Northern Ireland (NI) population over multiple time-points and their associations with all-cause mortality; receipt of psychotropic medication; and presentations to Accident and Emergency (A&E) departments. Based on linkage of NI GP registration, prescription, A&E and mortality data from 2010 to 2021, we used latent class growth analysis to identify trajectories in area-level deprivation from 2010 to 2016. Adjusting for baseline socio-demographic characteristics, we estimated the relationship between trajectories and health outcomes between 2017 and 2021. We identified three stable, two downwardly mobile and two upwardly mobile classes. Upward mobility was associated with reduced risk of poor health outcomes compared to the consistently deprived. Downward mobility was associated with higher risk of poor health outcomes compared to the consistently non-deprived. An approximate dose-response relationship was observed across classes, whereby lower 'endpoint' deprivation in 2016 was associated with lower risk of adverse outcomes. The exception was the 'substantial upward mobility' class, with risk of poor outcomes second highest despite improved deprivation rank in 2016. The classes of social mobility identified potentially provide a template within which social mobility can be studied in future research, highlighting the importance of both point of origin and destination in the study of social mobility and health.