title: Could strength of exposure to the residential neighbourhood modify associations between walkability and physical activity?
abstract: The importance of neighbourhoods for health and wellbeing may vary according to an individual's reliance on their local resources, but this assertion is rarely tested. We investigate whether greater neighbourhood 'exposure' through reliance on or engagement with the residential setting magnifies neighbourhood-health associations.
  
  
  METHODS
  Three built environment characteristics (destination density, streetscape (attractiveness of built environment) and street connectivity) and two physical activity components (weekday and weekend accelerometer counts) were measured for 2033 residents living in 48 neighbourhoods within four New Zealand cities in 2009-2010, giving six different built environment-physical activity associations. Interactions for each built environment-physical activity association with four individual-level characteristics (acting as proxies for exposure: gender, working status, car access, and income) were assessed with multi-level regression models; a total of 24 'tests'.
  
  
  RESULTS
  Of the 12 weekday built environment-physical activity tests, 5 interaction terms were significant (p < 0.05) in the expected direction (e.g. stronger streetscape-physical activity among those with restricted car access). For weekend tests, one association was statistically significant. No significant tests were contradictory. Pooled across the 12 weekday physical activity 'tests', a 1 standard deviation increase in the walkability of the built environment was associated with an overall 3.8% (95% CI: 3.6%-4.1%) greater increase in weekday physical activity across all the types of people we hypothesised to spend more time in their residential neighbourhood, and for weekend physical activity it was 4.2% (95% CI 3.9%-4.5%).
  
  
  CONCLUSIONS
  Using multiple evaluation methods, interactions were in line with our hypothesis, with a stronger association seen for proxy exposure indicators (for example, restricted car access). Added to the wider evidence base, our study strengthens causal evidence of an effect of the built environment on physical activity, and highlights that health gains from improvements of the residential neighbourhood may be greater for some people.
authors.affiliation: Health Inequalities Research Programme, Department of Public Health, University of Otago, Wellington, New Zealand. Electronic address: Vivienne.ivory@otago.ac.nz.
authors.forename: Vivienne C
authors.initials: VC
authors.lastname: Ivory
authors.affiliation: Health Inequalities Research Programme, Department of Public Health, University of Otago, Wellington, New Zealand. Electronic address: tony.blakely@otago.ac.nz.
authors.forename: Tony
authors.initials: T
authors.lastname: Blakely
authors.affiliation: Centre for Research on Environment, Society and Health, School of Geosciences, University of Edinburgh, Edinburgh, United Kingdom. Electronic address: jamie.pearce@ed.ac.uk.
authors.forename: Jamie
authors.initials: J
authors.lastname: Pearce
authors.affiliation: SHORE and Whariki Research Centre, School of Public Health, Massey University, Auckland, New Zealand. Electronic address: K.Witten@massey.ac.nz.
authors.forename: Karen
authors.initials: K
authors.lastname: Witten
authors.affiliation: Health Inequalities Research Programme, Department of Public Health, University of Otago, Wellington, New Zealand. Electronic address: nasser.bagheri@anu.edu.au.
authors.forename: Nasser
authors.initials: N
authors.lastname: Bagheri
authors.affiliation: McCaughey VicHealth Centre for Community Wellbeing, The University of Melbourne, Melbourne, Victoria, Australia; Centre for Physical Activity and Nutrition, Auckland University of Technology, Auckland, New Zealand. Electronic address: hannah.badland@unimelb.edu.au.
authors.forename: Hannah
authors.initials: H
authors.lastname: Badland
authors.affiliation: Centre for Physical Activity and Nutrition, Auckland University of Technology, Auckland, New Zealand. Electronic address: grant.schofield@aut.ac.nz.
authors.forename: Grant
authors.initials: G
authors.lastname: Schofield
mesh_terms: D000328:Adult; D000368:Aged; D004779:Environment Design / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D009520:New Zealand / Q000453:epidemiology; D012111:Residence Characteristics; D014504:Urban Health / Q000592:standards*; D016138:Walking
keywords: Built environment; Effect modification; Multilevel modelling; New Zealand; Physical activity; Walkability