The built environment and physical activity levels: the Harvard Alumni Health Study.
BACKGROUND
Physical activity is associated with better health, but many individuals are insufficiently active. Modifying the built environment may be an approach capable of influencing population-wide levels of physical activity, but few data exist from longitudinal studies that can minimize bias from active people choosing activity-friendly neighborhoods.


OBJECTIVE
This study aims to examine cross-sectional and longitudinal associations between the built environment and physical activity on a large scale.


METHODS
This study examined cross-sectional associations between urban sprawl (mapping addresses to corresponding counties) and physical activity (self-reported) among men throughout the U.S. in 1993 and in 1988, and longitudinal associations between changes in exposure to urban sprawl for movers and physical activity, 1988-1993. Included were 4997 men (mean age, 70 years) in the 1993 cross-sectional study; 4918 men in the 1988 cross-sectional study; and 3448 men in the longitudinal study, 1988-1993. Data were collected prospectively in 1988 and 1993, and analyses were performed in 2007-2008.


RESULTS
In cross-sectional analyses, less sprawl was significantly associated with more walking OR, comparing least with most sprawling areas, for meeting physical activity recommendations by walking=1.38 [95% CI=1.09, 1.76] in 1993 and 1.53 [1.19, 1.96] in 1988). Less sprawl also was associated with lower prevalence of overweight (corresponding OR=0.79 [0.64, 0.98] in 1993 and 0.81 [0.66, 1.00] in 1988). However, longitudinal analyses assessing change did not show that decreasing sprawl was associated with increased physical activity or decreased BMI.


CONCLUSIONS
These findings suggest that the cross-sectional results may reflect self-selection, rather than indicating that the built environment--as measured by urban sprawl--increases physical activity. However, the longitudinal findings were limited by small numbers of men changing residence and associated sprawl levels.
Lee
I-Min
IM
Division of Preventive Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02215, USA. ilee@rics.bwh.harvard.edu
Ewing
Reid
R
Sesso
Howard D
HD
D000368:Aged; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D004777:Environment; D015438:Health Behavior; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009765:Obesity / Q000453:epidemiology; D050177:Overweight / Q000453:epidemiology*; D011156:Population Density; D012307:Risk Factors; D014505:Urban Population / Q000706:statistics & numerical data*; D016138:Walking / Q000502:physiology