At age 19, many people are as inactive as 60-year-olds

By Sally Robertson, B.Sc.Jun 20 2017

A large proportion of teenagers get very little exercise and are as sedentary as 60-year-olds when they are just 19 years of age, according to a new study from the Johns Hopkins Bloomberg School of Public Health.

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The study looked at the variation in activity levels across five age groups: children (age six to 11); adolescents (12 to 19); young adults (20 to 29); middle-aged adults (31 to 59) and older adults (60 to 84).

The results showed that only after the age of 20 did people start to increase their activity levels and after age 35, activity started to decline and continued to do so throughout midlife and older adulthood.

The researchers used data from the National Health and Nutrition Examination Survey that included cycles of surveys carried out between 2003-2004 and 2005-2006. Information was available for 12,529 participants who had worn tracking devices for seven days in a row. The devices monitored physical activity levels at all times of day, apart from when they were removed for bathing or bedtime. They also measured how much time was spent engaging in no physical activity, light activity and moderate-to vigorous activity.

As reported in Preventive Medicine, more than 25% of male and 50% of female children did not meet the WHO recommendation for at least 60 minutes of moderate-to-vigorous physical activity a day. Among adolescents, 50% of males and 75% of females did not meet the recommendation.

Activity levels at the end of adolescence were alarmingly low, and by age 19, they were comparable to 60-year-olds.”

Senior author of the paper, Vadim Zipunnikov

The study also looked at how activity varied throughout the day and showed that among school-age children, the highest levels of activity were seen between two and six PM. The researchers say knowledge of these patterns could help inform interventions aimed at improving activity levels by ensuring they target periods where activity is lowest, rather than being based on age alone.

“The big question is how do we modify daily schedules, in schools for example, to be more conducive to increasing physical activity?" asks Zipunnikov.

Compared to adolescents, the only age group where increases in activity were seen was among the 20-somethings, where activity was spread throughout the day and peaked in the early morning.

The WHO recommendations are made with a focus on increasing moderate-to-vigorous activity, but the authors of the current study say reducing sedentary behavior in general and increasing even low-level exercise can be beneficial.

"Our study suggests that these efforts should consider time of day and also focus on increasing lower-intensity physical activity and reducing inactivity," Zipunnikov concludes.