Development of overweight and obesity among primary school children-a longitudinal cohort study

School health care is crucial for obesity prevention. Data on constancy of childhood obesity are still scarce, but highly necessary for risk evaluation. We examined from electronic health records (EHRs) the continuity of obesity during primary school and searched for social and behavioural characteristics associated with childhood obesity. From randomly selected 2000 Finnish sixth graders (aged 12-14), we identified 402 'ever overweight' and 172 'ever obese' children who were overweight or obese at least once since their first grade. These cohort data of growth measurements and the content of all pre-seventh grade health checks were retrospectively analysed from EHRs. Of the ever obese and ever overweight children, 69.3% (95% CI: 65.2-73.4%) continued to be overweight or obese in sixth grade. Of the ever obese children, nearly 40% were obese in first grade and 56% were obese or overweight in all six grades. Furthermore, 80% were obese or overweight already before school age. Obese children had experienced more bullying than overweight children (43.6% versus 30.8%, P = 0.003), had more frequently special needs for studying (25.6% versus 14.7%, P = 0.002) or had undergone a serious family crisis (20.3% versus 11.4%, P = 0.005). Electronic data on children's growth and psychosocial characteristics are potentially useful when aiming for early action to counter obesity. Such routinely collected data appear to be underutilized and should be further exploited both in individual and population level to develop screening and treatment processes.