Associations of residential walkability and greenness with arterial stiffness in the UK Biobank.

BACKGROUND: Arterial stiffness is a key non-invasive marker of early vascular ageing, however, little is known of its associations with urban built environment. We examined the associations of objectively-measured residential walkability and greenness with arterial stiffness in a large UK-wide population cohort. METHODS: We employed data from the baseline UK Biobank cohort comprising adult participants recruited over the period of 2006 to 2010. Residential walkability index, defined as a function of density (residential, retail and public transit), street-level design, and destination accessibility was measured using a 1-Km dwelling catchment, while greenness was modelled as the mean Normalized Difference Vegetation Index (NDVI) of 0.5-metre resolution assessed within a 0.5-Km catchment. Arterial stiffness index (ASI) was measured non-invasively from the pulse waveform. Linear regression models were developed to examine associations of walkability and greenness with arterial stiffness. Restricted cubic spline (RCS) models were developed to examine dose-response relationships. We also examined effect modifications by sex and age, as well as the interaction effect of greenness and walkability. RESULTS: This cross-sectional study used a target sample of 169,704 UK Biobank participants aged ≥ 39 years. After full adjustments, in reference to the lowest walkability exposure quartile, those in the highest were associated with lower ASI (β = -0.083 m/s, 95% CI: -0.14 to -0.03, p = 0.005). Participants in the third and fourth NDVI greenness exposure quartiles were also associated with lower ASI (β = -0.074 m/s, -0.14 to -0.01, p < 0.020 for the third and β = -0.293 m/s, -0.36 to -0.23, p < 0.001 for the fourth quartiles in reference to the first). The inverse association between NDVI greenness and ASI was more pronounced among women (p < 0.001), older adults (p = 0.011) and among participants in the highest walkability quartile (p < 0.001). CONCLUSION: Designing more walkable and greener residential environments can be a preventive intervention aimed at lowering the population distribution of vascular ageing and associated cardiovascular risks.