Higher amounts of time with moderate to vigorous physical activity were associated with better cardiometabolic risk factors, regardless of the amount of time spent sedentary, in a study that included data for more than 20,000 children and adolescents.

Many reports have suggested that higher amounts of time spent sedentary are associated with an adverse cardiometabolic risk profile. "However, the independent and combined associations between objectively measured time spent in moderate- to vigorous-intensity physical activity (MVPA) and time spent sedentary in relation to cardiometabolic risk factors in youth remain unclear," the authors wrote in background information in the article, which appears in the Feb. 15 issue of JAMA.

Ulf Ekelund, PhD, of the Institute of Metabolic Science in the United Kingdom, and colleagues examined the associations between MVPA and time spent sedentary with established cardiometabolic risk factors in children and adolescents. For the study, the researchers pooled data from 14 studies (between 1998 and 2009) comprising 20,871 children ages 4 to 18 from the International Children's Accelerometry Database.

The independent associations between time in MVPA and sedentary time with outcomes were examined using meta-analysis. Participants were stratified into one of three groups based on MVPA and sedentary time. The cardiometabolic measures used for the study included waist circumference, systolic blood pressure, fasting triglycerides, high-density lipoprotein cholesterol and fasting insulin levels.

Children spent an average of 30 minutes per day in MVPA and 354 minutes per day sedentary. Youth in the group that represented the top third of MVPA accumulated more than 35 minutes per day in this intensity level compared with fewer than 18 minutes per day for those in the low third.

The researchers found that time in MVPA was significantly associated with all cardiometabolic outcomes — waist circumference, systolic blood pressure, fasting insulin, fasting triglycerides and HDL cholesterol — independent of sex, age, accelerometer monitor wear time, time spent sedentary and waist circumference (when waist circumference was not the outcome). Time spent sedentary was not associated with any of the outcomes after additional adjustment for MVPA. The authors did note that "the differences in outcomes between higher and lower MVPA were greater the lower the sedentary time."

"Our results have implications for public health policy and physical activity counseling," they concluded. "Children should be encouraged to increase their participation in physical activity of at least moderate intensity rather than reducing their overall sedentary time as this appears more important in relation to cardiometabolic health.

"However, our measure of sedentary time takes into account the accumulated time spent sedentary rather than a specific behavior (e.g. TV viewing). Therefore, decreasing TV time in youth may still be an important public health goal as TV viewing may be associated with other unhealthy behaviors such as snacking and soft drink consumption."

The researchers added that moving from the group representing the bottom third of MVPA to the top third requires an increase in MVPA of at least 20 minutes per day. They said increasing daily activity at such an intensity level can be achieved through activities such as brisk walking, jogging, cycling and playing soccer and other team sports.

To read a study summary and access the study via subscription or purchase, visit http://bit.ly/wf2GY5.