Time Trends and Sociodemographic Factors Associated With Overweight and Obesity in Children and Adolescents in Spain.

Importance: Time-trend studies of overweight and obesity in childhood by sociodemographic factors are important for prioritizing public health initiatives. However, little is known about these trends in Spain, where high levels of obesity are found and where important demographic changes have occurred during the last 2 decades. Objective: To examine how time trends in the prevalence and incidence of overweight and obesity among children and adolescents differ by age, sex, socioeconomic status, urban/rural residence, and nationality. Design, Setting, and Participants: This cohort study included 1.1 million children and adolescents (aged 2-17 years) with at least 1 measure of height and weight in Catalonia, Spain, from 2006 to 2016. Electronic health records were accessed from the Information System for Research in Primary Care. Data analysis was conducted from January to December 2018. Main Outcomes and Measures: Prevalence and incidence rates and trends of overweight/obesity and obesity (overweight/obesity defined as having of BMI z score greater than 2.0 among children aged <5 years and greater than 1.0 among children aged ≥5 years; obesity defined as having of BMI z score greater than 3.0 among children aged <5 years and greater than 2.0 among children aged ≥5 years) between 2006 and 2016 were calculated and stratified by sociodemographic characteristics (ie, age, sex, deprivation index, urban/rural residence, and nationality). Results: The study population included 1 166 609 children and adolescents (570 982 [48.9%] girls; median [interquartile range] age at entry to electronic health record system, 2.4 [0-7.7] years; 1 006 892 [86.3%] with Spanish nationality). Of 941 041 children (80.7%) who lived in urban areas, 197 427 (20.7%) lived in the most deprived areas. Overall, the prevalence of overweight/obesity and obesity decreased between 2006 and 2016 in all sex and age groups; for example, among boys and girls aged 6 to 11 years, overweight/obesity prevalence decreased from 41.9% (95% CI, 41.5%-42.2%) to 39.9% (95% CI, 39.6%-40.3%) and from 39.7% (95% CI, 39.3%-40.2%) to 37.6% (95% CI, 37.3%-38.0%), respectively. Incidence rates of overweight/obesity and obesity were highest among children aged 6 to 7 years (overweight/obesity among boys: 11.9 [95% CI, 11.8-12.0] new cases per 100 person-years; obesity among boys: 4.9 [95% CI, 4.8-4.9] new cases per 100 person-years). Prevalence and incidence rates were highest in the most deprived areas, in urban areas, and among children with North, Central, or South American nationalities. Between 2006 and 2016, prevalence increased in the most deprived areas in almost all sex and age groups. Among girls aged 6 to 11 years living in the most deprived areas, the obesity prevalence ratio increased from 1.59 (95% CI, 1.46-1.74) to 2.03 (95% CI, 1.88-2.19) compared with those living in the least deprived areas. Furthermore, during this period, prevalence increased among children with non-Spanish nationalities, especially in the African and Asian nationality groups (eg, boys aged 6-11 years with Asian nationality compared with Spanish nationality, 2006: prevalence rate, 0.78 [95% CI, 0.60-1.01]; 2016: prevalence rate, 1.27 [95% CI, 1.15-1.39]). Incidence rates decreased among younger groups (eg, ≤7 years: incidence rate ratio for January 1, 2006, to June 30, 2011, vs July 1, 2011, to December 31, 2016: 0.94; 95% CI, 0.91-0.98) but remained stable in older groups. Conclusions and Relevance: In this study, the overall prevalence and incidence rates of childhood overweight/obesity and obesity slightly decreased during the last decade. However, increased deprivation disparities in childhood obesity were found, given that the prevalence increased among children living in deprived areas and with non-Spanish nationalities.