Cross-sectional associations between neighbourhood walkability and objective physical activity levels in identical twins

ObjectivesPhysical activity is a cornerstone of chronic disease prevention and treatment, yet most US adults do not perform levels recommended for health. The neighborhood–built environment (BE) may support or hinder physical activity levels. This study investigated whether identical twins who reside in more walkable BEs have greater activity levels than twins who reside in less walkable BEs (between-twin analysis), and whether associations remain significant when controlling for genetic and shared environmental factors (within-twin analysis).DesignA cross-sectional study.SettingThe Puget Sound region around Seattle, Washington, USA.ParticipantsThe sample consisted of 112 identical twin pairs who completed an in-person assessment and 2-week at-home measurement protocol using a global positioning system (GPS)monitor and accelerometer.ExposureThe walkability of each participants’ place of residence was calculated using three BE dimensions (intersection density, population density and destination accessibility). For each variable, z scores were calculated and summed to produce the final walkability score.OutcomesObjectively measured bouts of walking and moderate-to-vigorous physical activity (MVPA), expressed as minutes per week.ResultsWalkability was associated with walking bouts (but not MVPA) within the neighbourhood, both between (b=0.58, SE=0.13, p