Objective In this study, behavioural and social correlates of objectively measured sedentary time in young people were identified.

Design Cross-sectional analysis of data from the European Youth Heart Study (EYHS).

Setting Schools in Denmark, Estonia, Portugal and Norway.

Participants Respondents were invited using a twostage cluster sampling procedure. Analyses include 2107 children (9–10 years old) and adolescents (14–15 years old).

Assessment of independent variables Seven behavioural and 15 social variables assessed by parental and computerised child questionnaires.

Main outcome measure Sedentary activity as assessed by accelerometry (10 min blocks at <200 counts/min). Analyses were stratified by country, and interactions with grade and sex were investigated.

Results Adolescents were more sedentary than children (335.4 (90.4 min/day) vs 217.2 (75.6 min/day), p<0.001). Patterns of associations differed across countries. High computer use and no television viewing before school in Norway, and being sedentary during school breaks in Estonia were positively associated with sedentary time. No behavioural variables were associated with sedentary time in the Danish and Portuguese models. Socioeconomic position was positively associated with sedentary time in Portugal and Estonia, father's body mass index negatively in the Estonian model. Norwegian participants with a game console at home and Portuguese participants with a television in their bedroom were more sedentary.

Conclusions A single strategy aimed at reducing sedentary behaviour is unlikely to be effective across Europe as the target populations and behaviours of focus differ between countries. Targeting high socioeconomic groups in Portugal and Estonia or focusing on reducing computer use in Norway might be effective intervention strategies to reduce overall sedentary time.