[Sedentary behaviour 13-years-olds and its association with selected health behaviours, parenting practices and body mass].

Objective: 1. To estimate the time spent in sedentary behaviour (watching TV, using the computer, doing homework). 2. To assess the link between the total time spent on watching TV, using the computer, doing homework and dietary habits, physical activity, parental practices and body mass.

Material And Methods: Cross-sectional study was conducted in Poland in 2008 among 13-year olds (n=600). They self-reported their time of TV viewing, computer use and homework. Their dietary behaviours, physical activity (MVPA) and parenting practices were also self-reported. Height and weight were measured by school nurses. Descriptive statistics and correlation were used in this analysis.

Results: The mean time spent watching television in school days was 2.3 hours for girls and 2.2 for boys. Boys spent significantly more time using the computer than girls - respectively 1.8 and 1.5 hours, while girls took longer doing homework - respectively 1.7 and 1.3 hours. Mean screen time was about 4 hours in school days and about 6 hours during weekend, statistically longer for boys in weekdays. Screen time was positively associated with intake of sweets, chips, soft drinks, "fast food" and meals consumption during TV, and negatively with regularity of meals and parental supervision. There was no correlation between screen time with physical activity and body mass.

Conclusion: Sedentary behaviours and physical activity are not competing behaviours in Polish teenagers, but their relationship with unhealthy dietary patterns may lead to development of obesity. Good parental practices, both mother's and father's supervision seems to be crucial for screen time limitation in their children. Parents should become aware that relevant lifestyle monitoring of their children is a crucial element of health education in prevention of civilization diseases. This is a task for both healthcare workers and educational staff.