Longitudinal analysis of health disparities in childhood.

Objective: Combatting disparities in health outcomes among children is a major public health concern. This study focuses on two questions: (1) To what extent does socioeconomic status (SES) contribute to disparities in health outcomes? and (2) To what extent can social inequalities in health outcomes be explained by differences in children's health behaviours?

Design: This study included 2-year follow-up data of 1259 children (4-12 years of age) who participated in the 'Healthy Primary School of the Future' project (ClinicalTrials.gov NCT02800616). SES was measured by maternal and paternal education and household income (adjusted for family size). Health outcomes were body mass index (BMI) z-score, health resource use, school absenteeism, health-related quality of life and psychosocial health, measured over 2 years of follow-up (2015-2017). Health behaviours included physical activity, and consumption of fruits, vegetables and sweetened beverages. Associations between SES and baseline health behaviours were examined, and mixed models for repeated measures were used to assess associations between SES and health outcomes over 2 years of follow-up.

Results: A high socioeconomic background was significantly associated with better health outcomes (all outcomes). For example, children with a low SES had higher BMI z-scores (beta coefficient: 0.42, 95% CI 0.22 to 0.62) and higher consumption healthcare costs (ratio of mean costs: 2.21, 95% CI 1.57 to 3.10). Effects of SES changed very little after controlling for health behaviours.

Discussion: Our findings strongly suggest that socioeconomic background has a pervasive impact on disparities in child health, but gives little support to the idea that social inequalities in child health can be tackled by means of lifestyle interventions.