Variance Components In Sedentarism. A Study With Iscole Portuguese Children

Background: It well established that sedentarism (SED) adversely affects children´s health. Further, SED is a complex behavior and likely influenced by individual- and school-level predictors. The International Study of Childhood Obesity, Lifestyle, and Environment (ISCOLE) aims to determine the relationship between lifestyle characteristics and obesity in children, and to investigate the influence of behavioural settings and physical, social and policy environments on the observed relationships within and between countries.

Purpose: To determine the magnitude of variance components in SED of Portuguese ISCOLE children associated with individual and school-level predictors.

Methods: Seven hundred and seventy-six Portuguese children aged 10.5 years of both gender (boys=358; girls=418) were monitored during seven consecutive days for their physical activity levels using the Actigraph GT3X+ accelerometer. SED was defined as <100 counts per minute and daily averages in minutes were considered in all analyses. Individual-level variables included gender (G), BMI categories (normal weight and overweight/obese), maturity (MC) classes (on time and advanced), birth weight (BW), socioeconomic status (SES), and sleep/non-wear time (SNWT). School level variables included school size (SS), Interschool sports (IS), access to gymnasium (AG), and access to other large rooms (ALR). Variance components were estimated with multilevel modeling, and all computations were done in HLM 7.

Results: Individual-level variables explained 66.7% and school-level 3.7% of the total variance in SED. On average, boys were less sedentary than girls (b=-26.41±4.70min), those with higher SES were more sedentary (b=3.12±1.17min), and those who sleep more were less sedentary (b=-0.69±0.04min). MC, BMI categories and BW were not significant (p>0.05). At the school-level, only IS was significant (b=-5.71±2.59 min).

Conclusions: Since BMI categories, maturity status and birth weight have no influence on SED, children from lower SES, particularly girls, should be encouraged to participate in school sports programs to reduce their sedentary behaviors and adverse effects on their health.