Trends in social inequality in overweight and obesity among Danish infants between 2002-2022

Abstract Background Childhood overweight and obesity are a global health challenge. Evidence shows that childhood overweight and obesity are unevenly distributed across socioeconomic positions (SEP), but trends in social inequality in childhood overweight and obesity are inconclusive. We aimed to examine trends in relative and absolute social inequality in overweight and obesity among Danish infants born between 2002 and 2022. Methods The study applied yearly cross-sectional data on infants’ weight and length at age 6-10 months documented by community health nurses (n = 63,100). Data was linked with parental education from population registers. Social inequality in overweight and obesity was measured by odds ratio (OR), relative index of inequality (RII), and slope index of inequality (SII). Trend tests measured changes over time. Results The overall prevalence of overweight and obesity increased from 3.5% to 6.0% between 2002 and 2022. No difference in odds for overweight and obesity by parental education was observed between 2002 and 2004, but from 2005, social inequality in overweight and obesity at age 6-10 months was revealed. The OR for overweight and obesity ranged from 1.20 (95% CI: 0.76-1.89) to 2.31 (95% CI: 1.64-3.25) for infants of parents with lowest level of educational attainment. RII ranged from 0.78 to 0.41 (test for trend, p = 0.179) and SII ranged from -0.92 to -4.54 (test for trend, p = 0.026) indicating persistent relative social inequality and an increase in absolute social inequality in overweight and obesity from 2002 to 2022. Conclusions The study revealed persistent relative social inequality and increased absolute social inequality in overweight and obesity among Danish infants from 2002 to 2022. The study indicated that social inequality in overweight and obesity starts within the first year of life, emphasizing the crucial need for early interventions. Key messages • Relative social inequality in overweight/obesity remained persistent, while absolute social inequality increased from 2002-2022. • Social inequality in overweight/obesity already exists in the first year of life, highlighting the need for early interventions.