Teenager on couch with laptop and phone
June 19, 2017

19-year-olds are as sedentary as their grandparents, study finds

The average teenager is no more physically active than sexagenarians, and the only time of life that activity levels will increase for most people is between the ages of 20 and 35, according to new research from the Johns Hopkins Bloomberg School of Public Health.

Published online earlier this month in the journal Preventive Medicine, the study found that from childhood to adolescence (ages 6 to 19), physical activity levels were significantly lower due to a later start of morning activity and that overall activity levels declined again starting at age 35.

During young adulthood (between the ages of 20 and 30), total and light intensity activity went up by age. It then began to stabilize starting at age 31 due to earlier initiation of morning activity, according to senior author Vadim Zipunnikov, an assistant professor in the Bloomberg School's Department of Biostatistics, and his colleagues explained in their study.

“Activity levels at the end of adolescence were alarmingly low, and by age 19, they were comparable to 60-year-olds,” Zipunnikov said in a statement. “For school-age children, the primary window for activity was the afternoon between two and six P.M.”

“So the big question is how do we modify daily schedules, in schools, for example, to be more conducive to increasing physical activity?” he added. “The goal of campaigns aimed at increasing physical activity has focused on increasing higher-intensity exercise. Our study suggests that these efforts should consider the time of day and also focus on increasing lower-intensity physical activity and reducing inactivity.”

Males more active in most cases, but not among older adults

As part of their research, Zipunnikov’s team analyzed data gathered as part of the National Health and Nutrition Examination Survey in 2003-2004 and 2005-2006. A total of 12,529 people were involved in the study, and each wore tracking devices that measured their activity levels – and conversely, how sedentary they were – each day.

The data was broken down into five age categories: children (ages six to 11); adolescents (ages 12 to 19); young adults (ages 20 to 29); adults at midlife (ages 31 to 59); and older adults (age 60 through age 84), the researchers said. Fifty-one percent were female, 49% were male.

Among the young adult group, the only group in which an increase in activity levels was spotted, the researchers found that their activity was spread throughout the entire day, although there was a noted rise in early-morning physical activity compared to adolescents. The authors believe that this phenomenon is due to life transitions, such as finding full-time employment.

Furthermore, the study also found that males typically had higher activity levels than females, but that they also experienced an earlier lowering in activity levels by midlife. Among those aged 60 and above, males were more sedentary and had lower light-intensity activity levels compared to females.

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