Children in the U.K. spend over 80% of their days in a sedentary fashion, and higher weight, as well as having an older father, are risk factors for that behavior, a cohort study found.

The mean daily counts per minute of physical activity, as measured by accelerometer, was 669 and was significantly higher in boys (P=0.002), reported Mark Pearce, PhD, of Newcastle University in Newcastle upon Tyne in England, and colleagues in the June issue of PLoS One.

The mean daily counts per minute of physical activity was significantly reduced with older paternal age (P=0.01), winter season (P<0.001), and elevated body mass index (P=0.003), they also said.

The more time children dedicated to extracurricular sports activities, the less time they had for sedentary behaviors, the authors explained.

The study gathered data through the Gateshead Millennium Study, which was a cohort of over 1,000 children born from 1999 to 2000 in Gateshead, England, that looked to identify predictors of childhood physical activity.

Data collected on infants included sex, birth weight, maternal and paternal ages at birth, socioeconomic status, and whether they were ever breastfed at 6 weeks and at 4, 8, and 12 months. Participants were measured again between ages 8 and 10 for body mass index (BMI), time spent playing video games or watching television, any parental time restrictions on television watching, and time spent in after-school sports clubs.

Physical activity measures were taken through accelerometers, which were attached to a waist belt and worn by the 8- to 10-year-olds for 7-day periods after waking and removed before going to bed. Readings were broken down into periods of physical activity, moderate-to-vigorous physical activity (MVPA), and sedentary behavior.

The average time spent in moderate-to-vigorous physical activity was 4% of each day, while participants spent 80.6% of their day sedentary, Pearce and colleagues found.

Boys spent more time in moderate-to-vigorous physical activity than girls (mean difference 1.2%, 95% CI 0.8% to 1.7%, P<0.001) and were less sedentary than girls (mean difference 2.5%, 95% CI 1.5% to 3.4%, P<0.001).

Significant associations with reduced MVPA and more increased sedentary time were seen with:

• Older paternal age: effect size of -0.03% per year (95% CI -0.07% to -0.003, P=0.03 for MVPA) and 0.1% (95% CI 0.02% to 0.17%, P=0.02 for sedentary behavior)
• Elevated BMI: -0.4% per standard deviation score (95% CI -0.6 to -0.2 P<0.001) and 0.5% (95% CI 0.1% to 0.9% P=0.03)
• Season: participants were less active in winter than in other seasons (P<0.001 for both)

Time spent in MVPA was also reduced when parents restricted television viewing (P=0.05).

Each additional minute per week of after-school sports was associated with a positive impact on time spent in MVPA and negative time in a sedentary state (effect size 0.002% per minute per week, 95% CI 0.00 to 0.01 and -0.01%, 95% CI -0.01 to -0.001, P=0.05 for both).

When adjusted for BMI, the following factors maintained a significant association with sedentary time:

• Paternal age
• Sex
• Season
• Time spent in after-school sports clubs

The low mean MVPA time was "not restricted to children in this study ... but is reported from diverse locations," the authors wrote.

The researchers noted a number of limitations with their research, including the bi-directional effects of BMI on outcome measures, the potential lack of generalizability of results, and the standard deviation's effect on effect size.

They suggested that additional exploration of the sex differences in physical activity would be helpful, as would encouraging children to join out-of-school sports clubs.

Source reference:
Pearce M, et al "Early predictors of objectively measured physical activity and sedentary behaviour in 8-10 year old children: the Gateshead Millennium Study" PLoS One 2012; 7: e37975.