Abstract: Objective: Study on the relationship of built-in environmental factors to outdoor physical activity and sedentary time in urban elderly. Methods: 586 urban elderly of over 60 years old (male 258, female 328) wore Actigraph accelerometer for 4 days and their high intensity outdoor physical activity and sedentary time were measured by the GIS technology on 9 built-in environmental indexes including population density, building density, street connectivity, total road length per capita, mixed utilization of land, number of traffic stations, distance to traffic station, distance to fitness and leisure place, distance to business place within 1 km buffer zone to the family address of effective sample population. The variables were then divided into the three levels of 1, 2 and 3 according to the two percentiles of 33 and 66, and the demographic variables were integrated into the logistic model as control variables. Results: As the mixed utilization of land decreases from one level to the next, the estimated coefficient β of the change in outdoor physical activity level is 1.122,P=0.016 and 0.762,P=0.036 respectively, and the estimated coefficient of change in the number of traffic stations from level 1 to level 3 is 0.720,P=0.029. The estimated coefficient of change in distance to traffic station from level 2 to level 3 is 0.769, P=0.049. There is no correlation between other built-in environmental factors and the outdoor physical activity of the elderly. As the population density decreases by one level, the estimated coefficient β of the sedentary time is 0.745, P=0.004 and 0.751, P=0.014 respectively, and the estimated coefficient of change in the total road length per capita from level 2 to level 3 is 0.926 and P=0.029. There is no correlation between other built-in environmental factors and the sedentary time of the elderly. Conclusion: The built-in environmental factors affecting the daily physical activity of the elderly are: mixed utility of land, distance to the fitness place, number of traffic stations, and distance to the traffic station. The built-in environmental factors that affect the elderly's daily sedentary time are: population density and total road length per capita. Therefore, when the planning departments redesign the planning policy, they can improve the daily physical activity of the elderly, change the sedentary lifestyle and improve their health level in the coming aging society of China by coping with the above-mentioned built-in environmental factors.

Key words: physical activity, built-in environment, elderly, sedentary, accelerometer, GIS