Objectives To determine age and gender differences in health-related quality of life (HRQOL) in children and adolescents across 12 European countries using a newly developed HRQOL measure (KIDSCREEN). Methods The KIDSCREEN-52 questionnaire was filled in by 21,590 children and adolescents aged 8-18 from 12 countries. We used multilevel regression analyses to model the hierarchical structure of the data. In addition, effect sizes were computed to test for gender differences within each age group. Results Children generally showed better HRQOL than adolescents (P \ 0.001). While boys and girls had similar HRQOL at young age, girls' HRQOL declined more than boys' (P \ 0.001) with increasing age, depending on the HRQOL scale. There was significant variation between countries both at the youngest age and for age trajectories. Conclusions For the first time, gender and age differences in children's and adolescents' HRQOL across Europe were assessed using a comprehensive and standardised instrument. Gender and age differences exist for most HRQOL scales. Differences in HRQOL across Europe point to the importance of national contexts for youth's well-being.

SummaryObjectives: To assess whether gender and age differences can be found in different aspects of health-related quality of life Results: Children report a very good quality of life largely independent of gender. After 12 years, HRQOL decreases in the majority of aspects. In the physical and psychological dimensions, a stronger decrease is found for females than for males. Conclusions:Children have higher HRQOL than adolescents in many aspects. With increasing age, HRQOL is frequently worse for females than for males. Examination of the individual aspects leads to a differentiation of the results with relevance for public health.

There is evidence to suggest that exposure to low parental educational status may result in a decreased HRQoL in childhood, whereas reduced access to material (and thereby social) resources may lead to a lower HRQoL especially in adolescence.

Background: The objective of the present study was to compare three different sampling and questionnaire administration methods used in the international KIDSCREEN study in terms of participation, response rates, and external validity.