Trading-Off Transit and Non-Transit Physical Activity among Older People: Evidence from Longitudinal Accelerometer Data of a Natural Experiment Study

This study used a natural experiment of a new metro line in Hong Kong to examine trade-offs between transit-related and non-transit-related physical activity (PA) among 104 older people (aged ≥ 65 years) based on longitudinal accelerometer data that distinguished transit-related and non-transit-related PA. Difference-in-difference (DID) analysis compared PA changes between treatment and control groups. We found that new metro stations have trade-off effects between transit and non-transit PA. After opening metro stations, transit-related PA increased by 12 min per day on average, but non-transit-related PA decreased by 18 min per day. In addition, the proportion of time spent in transit-related PA increased by 6%. The results suggested that new metro stations could generate transit-related PA, but it might shift from non-transit-related PA among older people. Our findings revealed trade-off effects of public transit interventions and have significant implications for transport and healthy ageing studies.