The sample consisted of 1554 girls, including 4% Asian, 21 % African American, 22% Hispanic, 45% white, and 8% mixed race or Native American. shows the number of girls by distance category from school. Only 15.5% lived within 1 mile of the school; 28% lived 1 to 2 miles from school, 23% lived 2 to 3 miles from school, 24% lived 3 to 5 miles from school, and 9% lived more than 5 miles away. The farthest distance from school varied considerably by site ranging from 7.4 miles in Minneapolis, MN to approximately 20 miles in Tucson, AZ. Overall, only 4% of the girls lived within a half-mile of school, although in New Orleans 20% lived within this radius.
Number of girls by category of distance from school
shows the unadjusted minutes of MW-MVPA by distance categories from school. In each category, minutes of MW-MVPA are shown for total time not in school, after school time on weekdays, and weekend time. The patterns indicate an inverse relationship such that total and weekday non-school MW-MVPA declined as girls lived further away. In contrast, a 1-way ANOVA test for differences in the average value by distance showed that MW-MVPA on the weekends was similar across all the distances (P = 0.96). Considering only the time after 3 PM on weekdays, girls living 5 to 6 miles from school had 58 fewer MW-MVPA minutes per week than girls living within a ½ mile of the school.
Minutes of MET-weighted MVPA by distance from school
Because time after 3 PM did not include minutes that may have been spent in physical activity before school, we used total weekday MW-MVPA for our non-linear model. Here we collapsed distance to school into four categories based upon the observed differences in MET-weighted MVPA: 0 to less than ½ mile from school, ½ to less than 5 miles, 5 miles to less than 10 miles, more than 10 miles. shows the results of the adjusted non-linear model. In addition to exponentiated coefficient estimates, the table presents the effect size of the coefficient at the average MW-MVPA for girls living within ½ mile of school. For example, girls living ½ mile to 5 miles from school have, on average, 11.8% less total MW-MVPA for the week than girls living within ½ mile of school. The average girl living within ½ mile had 852 MW-MVPA minutes per week. In contrast, the average girl living ½ to 5 miles from school, had 101 fewer MW-MVPA for the week (11.8% of 852). Minutes of MW-MVPA did not differ significantly among girls within this range. Girls living 5 to 10 miles from school had 19.7% fewer MW-MVPA minutes per week (a difference of 168 MET-min per week) than girls living within ½ mile, and girls living more than 10 miles away had 54.2% fewer (a difference of 462 MET-rnin per week).
Non-Linear Model Predicting Total MET-Weighted MVPA for the Entire Week
The results are even more striking for MW-MVPA during the school week (). Girls ½ to 5 miles from school had 14% fewer MW-MVPA minutes per week of physical activity than girls within ½ mile, while girls 5 to 10 miles had 21% fewer and those more than 10 miles away had 62% fewer.
Non-Linear Model Predicting Total MET-Weighted MVPA for Weekdays
shows the coefficient estimates for a model predicting MW-MVPA during weekdays at three different units of geography with a linear specification for distance. In these models we assume a constant effect of distance from school. The findings are similar across all three models, and show consistent associations between MW-MVPA and distance to school as well as large associations between MW-MVPA and race/ethnicity. The effect sizes for MW-MVPA are very similar for all geographic units and range from 12.8 to 14.6 MW-MVPA minutes per week per mile away from school.
Full Model Predicting Weekday MET-Weighted MVPA by Block Group, Census Tract, and 1/2-Mile Radius Neighborhoods