Population trajectories and age-dependent associations of obesity risk factors with body mass index from childhood to adolescence across European regions: A two-cohort study.

Objective: To investigate population trajectories of behavioural risk factors of obesityfrom childhood to adolescence and their associations with body mass index (BMI)in children across European regions.Methods: Data were harmonised between the European multi-centre IDEFICS/I.Family and the Amsterdam Born Children and their Development Cohort. Participantswere aged 2.0-9.9 and 5.0-7.5 years at baseline, respectively, and were followeduntil age 18 years. Behavioural risk factors of interest included diet, physical activity,media use and sleep. Mixed effects models were used for statistical analyses toaccount for repeated measurements taken from the same child.Results: The study included a total of 14 328 individuals: 4114, 4582, 3220 and2412 participants from Northern, Southern, Eastern Europe and Amsterdam,respectively. Risk factor means and prevalences changed with age, but thetrajectories were mostly similar across regions. Almost no associations betweenbehavioural factors and BMI were found at the age of 6 years. At 11 years, dailysugar-sweetened foods consumption, use of active transport, sports club membershipand longer nocturnal sleep duration were negatively associated with BMIin most regions; positive associations were found with media use. Most associationsat 11 years of age persisted to 15 years.Conclusions: Whilst population trajectories of media use and nocturnal sleepduration are similar across European regions, those of other behavioural risk factorslike active transport and daily vegetable consumption differ. Also, associationsbetween behavioural risk factors and BMI become stronger with age andshow similar patterns across regions.