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

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. 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. 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). 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.