Longitudinal trajectories of quality of life among people with mild-to-moderate dementia: a latent growth model approach with IDEAL cohort study data

Abstract

Objectives: We aimed to examine change over time in self-rated quality of life (QoL) in people with mild-to-moderate dementia and identify sub-groups with distinct QoL trajectories. Method: We used data from people with mild-to-moderate dementia followed up at 12 and 24 months in the IDEAL cohort study (baseline n=1537). A latent growth model approach examined mean change over time in QoL, assessed with the QoL-AD scale, and investigated associations of baseline demographic, cognitive and psychological covariates with the intercept and slope of QoL. We employed growth mixture modelling to identify multiple growth trajectories. Results: Overall mean QoL scores were stable and no associations with change over time were observed. Four classes of QoL trajectories were identified: two with higher baseline QoL scores, labelled Stable (74.9%) and Declining (7.6%), and two with lower baseline QoL scores, labelled Stable Lower (13.7%) and Improving (3.8%). The Declining class had higher baseline levels of depression and loneliness, and lower levels of self-esteem and optimism, than the Stable class. The Stable Lower class was characterised by disadvantage related to social structure, poor physical health, functional disability, and low psychological well-being The Improving class was similar to the Stable Lower class but had lower cognitive test scores. Discussion: Understanding individual trajectories can contribute to personalised care planning. Efforts to prevent decline in perceived QoL should primarily target psychological well-being. Efforts to improve QoL for those with poorer QoL should additionally address functional impairment, isolation, and disadvantage related to social structure.