[Sedentary Behavior and the health of adolescents].

BACKGROUND: In modern societies, adolescents spend about half of their waking hours with sedentary behavior (SB). Therefore, the current study aims at investigating the relationship between SB and adolescents' health.

METHODS: A cross-sectional sample of 1296 students (8(th) grade) from 29 schools in Schleswig-Holstein, Germany was surveyed. Mean age was 13.75 years (SD = 0.67), 47.0 % were female. To asses screen-based and non-screen-based SB, moderate to vigorous physical activity as well as further indicators of health behavior (tobacco and alcohol use, diet) a questionnaire was used. Anthropometric data and blood pressure at rest were assessed during a medical testing and cardiorespiratory fitness was assessed by the 20 m-Shuttle-Run-Test.

RESULTS: The students spent almost 7 hours a day sedentary. Total SB was positively associated with behavior that is detrimental to health. These associations were detectable only for screen-based SB, not for non-screen-based SB. Cardiorespiratory fitness was associated negatively with total SB, screen-based as well as non-screen-based SB. Associations remained widely stable when moderate to vigorous physical activity was controlled for. There were almost no associations between SB and blood pressure.

DISCUSSION: Total SB, but especially screen-based SB seems to be a health risk factor in adolescence independent of physical activity. Besides fostering physical activity, reduction of SB should be a core target behavior in prevention and health promotion.