Neighbourhood walkability and incidence of hypertension: Findings from the study of 429,334 UK Biobank participants.

BACKGROUND With an estimated one billion hypertension cases worldwide, the role of the built environment in its prevention and control is still uncertain. The present study aims to examine the associations between neighbourhood walkability and hypertension in a large and diverse population-based cohort. MATERIALS AND METHODS We examined the association between neighbourhood walkability and blood pressure outcomes for N = 429,334 participants drawn from the UK Biobank and aged 38-73 years. Neighbourhood walkability was objectively modelled from detailed building footprint-level data within multi-scale functional neighbourhoods (1.0-, 1.5- and 2.0-kilometer street catchments of geocoded dwelling). A series of linear and modified Poisson regression models were employed to examine the association between walkability and outcomes of diastolic blood pressure (DBP in mmHg), systolic blood pressure (SBP in mmHg) and prevalent hypertension adjusting for socio-demographic, lifestyle and related physical environmental covariates. We also examined the relationship between walkability and change in blood pressure for a sub-sample of participants with follow-up data and tested for interaction effects of age, sex, employment status, neighbourhood SES, residential density and green exposure. RESULTS Neighbourhood walkability within one-kilometer street catchment was beneficially associated with all the three blood pressure outcomes, independent of all other factors. Each interquartile increment in walkability was associated with the lower blood pressure outcomes of DBP (β = -0.358, 95% CI: -0.42, -0.29 mmHg), SBP (β = -0.833, 95% CI: -0.95, -0.72 mmHg) as well as reduced hypertension risk (RR = 0.970, 95% CI: 0.96, 0.98). The results remained consistent across spatial and temporal scales and were sensitive to sub-groups, with pronounced protective effects among female participants, those aged between 50 and 60 years, in employment, residing in deprived, high density and greener areas. CONCLUSION This large population-based cohort found evidence of protective association between neighbourhood walkability and blood pressure outcomes. Given the enduring public health impact of community design on individual behaviour and lifestyle, of particular interest, are the targetted upstream-level interventions in city design aimed at optimizing walkability. Further long term studies are required to assess its sustained effects upon hypertension prevention and control.