title: The effect of light rail transit on body mass index and physical activity.
abstract: BACKGROUND
  The built environment can constrain or facilitate physical activity. Most studies of the health consequences of the built environment face problems of selection bias associated with confounding effects of residential choice and transportation decisions.
  
  
  OBJECTIVE
  To examine the cross-sectional associations between objective and perceived measures of the built environment; BMI; obesity (BMI>30 kg/m(2)); and meeting weekly recommended physical activity (RPA) levels through walking and vigorous exercise. To assess the effect of using light rail transit (LRT) system on BMI, obesity, and weekly RPA levels.
  
  
  METHODS
  Data were collected on individuals before (July 2006-February 2007) and after (March 2008-July 2008) completion of an LRT system in Charlotte NC. BMI, obesity, and physical activity levels were calculated for a comparison of these factors pre- and post-LRT construction. A propensity score weighting approach adjusted for differences in baseline characteristics among LRT and non-LRT users. Data were analyzed in 2009.
  
  
  RESULTS
  More-positive perceptions of one's neighborhood at baseline were associated with a -0.36 (p<0.05) lower BMI; 15% lower odds (95% CI=0.77, 0.94) of obesity; 9% higher odds (95% CI=0.99, 1.20) of meeting weekly RPA through walking; and 11% higher odds (95% CI=1.01, 1.22) of meeting RPA levels of vigorous exercise. The use of LRT to commute to work was associated with an average -1.18 reduction in BMI (p<0.05) and an 81% reduced odds (95% CI=0.04, 0.92) of becoming obese over time.
  
  
  CONCLUSIONS
  The results of this study suggest that improving neighborhood environments and increasing the public's use of LRT systems could provide improvements in health outcomes for millions of individuals.
authors.affiliation: Department of Criminology, University of Pennsylvania, Philadelphia, 19104-6286, USA. johnmm@sas.upenn.edu
authors.forename: John M
authors.initials: JM
authors.lastname: MacDonald
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Stokes
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Cohen
authors.forename: Aaron
authors.initials: A
authors.lastname: Kofner
authors.forename: Greg K
authors.initials: GK
authors.lastname: Ridgeway
mesh_terms: D000328:Adult; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D009657:North Carolina / Q000453:epidemiology; D012111:Residence Characteristics; D014186:Transportation / Q000379:methods*; D016138:Walking