Six decades of trends in BMI, thinness, overweight, and obesity among 210,927 Swedish children in different socioeconomic contexts.

BACKGROUND: Childhood obesity and low socioeconomic status increase the risk for adverse health outcomes. Societal changes may have altered the association between parental socioeconomic factors and childhood obesity over time. Our aim was to evaluate the trends for BMI in girls and boys 1952-2017 and the importance of socioeconomic factors for the BMI trend 2002-2017. METHODS: We used the population-based BMI Epidemiology Study cohort with information on BMI for seven-year-old children between 1952 and 2017 in Gothenburg, Sweden. We included in total 210,927 children and assessed the overall trend as well as in different socioeconomic strata. Data on parental country of birth, educational level, and income were available for a subpopulation between 2002 and 2017 (n = 65,556). RESULTS: Childhood BMI trends showed four distinct phases: a modest increase 1952-1973, a steep increase 1974-2001, a brief period of decline 2002-2006, followed by diverging trends 2008-2017 that differed by parental socioeconomic strata. In the latter period, children with Swedish-born parents, high educational level, and high income displayed a stabilising trend, whereas children with parents born outside Sweden, with low educational level, and low income showed increasing BMI trends. Parental low educational level had the most pronounced increasing BMI trend in their children, regardless of income and country of birth. CONCLUSIONS: After increasing BMI and a brief period of decline, we found widening socioeconomic disparities in childhood BMI 2008-2017, with the most pronounced increases among children whose parents had low educational level. These findings highlight the need for targeted interventions.