Objective and subjective measures of the neighbourhood environment: associations with frailty levels

Available online 14 September 2020OBJECTIVES: The aim of this study was to investigate whether perceptions of the neighbourhood environment (NE) and objective measures of the NE were associated with frailty in older adults. METHODS: A cross-sectional study in Adelaide, Australia, recruited a sample of 115 community-dwelling adults aged ≥60 years. Respondents’ perceptions of their NEs were assessed using the Neighbourhood Environment Walkability Scale (NEWS). An objective assessment of these NEWS survey questions was conducted using seven variables: residential density, land use mix diversity, street connectivity, accessibility, seasonal persistent green cover, road crash density and crime rate. Frailty was evaluated using the FRAIL (fatigue, resistance, ambulation, illnesses and loss of weight) scale. Multivariable linear regression analyses were employed to assess the associations between NEWS and frailty, and to assess the associations between objective neighbourhood variables and frailty. RESULTS: Frail and pre-frail older adults were more likely to live in areas with lower residential density, lower density of road crashes, and higher accessibility than robust participants. Additionally, a poorer perception of the overall environment, worse land-use mix and accessibility and worse crime safety were associated with frailty and pre-frailty after adjustment of covariates and objective GIS variables. DISCUSSION: Neighbourhood characteristics, both objective and perceived, are associated with frailty levels in older adults, and that strategies to tackle frailty must consider the impact of the neighbourhood environment.Beatriz Arakawa Martins, Danielle Taylor, Helen Barrie, Jarrod Lange, Kareeann Sok Fun Kho, Renuka Visvanatha

Equivalent diffusion coefficient and equivalent diffusion accessible porosity of a stratified porous medium

Diffusion is an important transport process in low permeability media, which play an important role in contamination and remediation of natural environments. The calculation of equivalent diffusion parameters has however not been extensively explored. In this paper, expressions of the equivalent diffusion coefficient and the equivalent diffusion accessible porosity normal to the layering in a layered porous medium are derived based on analytical solutions of the diffusion equation. The expressions show that the equivalent diffusion coefficient changes with time. It is equal to the power average with p = -0.5 for small times and converges to the harmonic average for large times. The equivalent diffusion accessible porosity is the harmonic average of the porosities of the individual layers for all times. The expressions are verified numerically for several test cases