Clocking disparities in youth sedentary time 

In a world full of screen time, it’s important to keep kids moving. Many school and extracurricular programs promote active and healthy behaviors designed to reduce how much time youth spend sitting or motionless. Still, disparities remain between boys and girls and across racial and ethnic groups in the amount of sedentary time they experience.  

A new study from University of Illinois Chicago researchers dug deeper into these differences by looking at when and where these disparities emerge. Using a dataset where thousands of children between the ages of 6 and 18 wore accelerometers — similar to the technology in a fitness tracker — for a week, a team led by graduated PhD student María Enid Santiago-Rodríguez analyzed the times of day when groups differed in activity. 

The study, published in PLoS ONE, identified two time periods of interest. Weekday school hours were responsible for more than half of the sedentary time disparities between girls and boys, with after-school hours and weekday evenings contributing another 30% of the difference.  

“Even though they’re only spending a quarter of their week at school, two-thirds of the disparity between boys and girls is happening during those school hours,” said Eduardo Esteban Bustamante, assistant professor of kinesiology and nutrition in the College of Applied Health Sciences and senior author on the paper.

While surprising, given that students of both sexes should experience mostly the same routine during the school day, the result also offered promise for intervention. 

“School is a time where you can reach most of the students,” said Santiago-Rodríguez. “So I think it is a very unique opportunity that we can take advantage of to reduce those sex disparities.” 

Across racial and ethnic groups, weekend mornings emerged as the largest contributor to disparities. In some comparisons, such as between Mexican American and Black youth, two-thirds of the difference happened on weekends versus weekdays. 

“That was startling, because it happens over only two days of the week,” Bustamante said. “It suggests that we need to work with families and with parents and think about what’s happening at home to address those disparities. At school, your ceiling for impact is much lower.” 

Through his Healthy Kids Lab, Bustamante has developed a family intervention called BUILT that offers activity suggestions for out-of-school hours. The new research will help the organizers of such programs apply them when they would be most effective and help scientists like Santiago-Rodríguez focus in on the underlying causes of these disparities, examining gender norms, cultural values and neighborhood resources. 

“It’s hard to tell the why, because there is not enough qualitative data among this age group,” said Santiago-Rodríguez, who is now a postdoctoral researcher at the University of Michigan. “But now we can tell which time of the day to prioritize.”