Neighbourhood Physical Environment, Intrinsic Capacity and 4-Year Late-Life Functional Ability Trajectories: A Longitudinal Study with the Parallel Process of Latent Growth Curve Modelling

Background: Knowledge on how intrinsic capacity (IC) and neighbourhood physical environment shape functional ability (FA) trajectories in later life remains understudied. We investigated the 4-year trajectories of IC and their impact on FA trajectories, and the associations between neighbourhood physical environments and FA trajectories over time among older adults. 

Methods: We conducted a four-wave longitudinal study from 2014-2017 in Hong Kong with 2,081 adults aged 65 and above. FA was assessed by The Chinese Lawton Instrumental Activities of Daily Living. We used cognition, affect, locomotion, sensory capacity, and vitality to capture multi-domains of IC . Neighbourhood physical environment attributes included green space, land use diversity, and facilities availability, assessed within 200- and 500-meter buffers of respondents' homes. The parallel process of latent growth curve modelling was used. 

Findings: IC (β = -0·022, p<0·001) and FA (β = -0·196, p<0·001) each decreased significantly over time. Individuals with declines in IC experienced faster declines in FA over time. Green space within a 200-meter buffer (β = 1·15, p = ·023), the number of leisure facilities (β = 0·03, p = ·043) and public transport (β = ·08, p = ·003) with a 500-meter buffer slowed the decreasing FA rate. 

Interpretation: The level of FA decreased over time in later life. The changes of IC shaped FA trajectories. The more residential green space and the number of leisure facilities and public transport in the neighbourhood may help slow declines of FA over time.