Socioeconomic Disparities in Obesity Expanded Over Past 2 Decades

Kosuke Inoue, MD, PhD

New findings suggest socioeconomic disparities in obesity have widened in the last 2 decades, marking it as a significant public health concern.

The trends show the rates of adjusted obesity prevalence increased from 1999 - 2018 and were particularly prevalent among adolescents in the United States from low socioeconomic households.

“Accordingly, the larger obesity prevalence among adolescents from lower-SES households may exacerbate socioeconomic disparities in chronic diseases into adulthood,” wrote study author Kosuke Inoue, MD, PhD, Department of Social Epidemiology, Graduate School of Medicine, Kyoto University.

The study investigators evaluated obesity trends over this 2-decade period and stratified by household income and head of household education level. The data was compiled from the 1999 - 2018 National Health and Nutrition Examination Surveys (NHANES).

The rates of obesity among adolescents (aged 10 - 19 years) was defined as age- and sex-specific body mass index (BMI) greater than or equal to the 95th percentile based on the 2000 Centers for Disease Control and Prevention growth charts.

Individuals were stratified by household income (≤138% vs >138% federal poverty level) and head of household education level. Additionally, data on race and ethnicity were included on the association with obesity prevalence among US children and adolescents.

The team of investigators first described 1999 - 2018 trends in obesity prevalence in 4-year increments stratified by income and education. Then, they investigated the association of socioeconomic status and obesity prevalence using ordinary least-squares regression.

There were a total of 21,296 individuals included in the study, with a mean age of 14.5 years and 49.3% were female. Investigators noted the information on household income and head of household education levels were available for 19,465 (91.0%) and 20,302 (95.0%), respectively.

Data show adolescents from low-socioeconomic status households were more likely to be non-Hispanic Black (21.7%), have obesity (22.8%), or have an unmarried parent (45.5%). Trends in adjusted obesity prevalence increased over 20 years, with a particular prevalence among adolescents from low-socioeconomic status households.

Investigators noted that living in a low-income household was associated with a 4.2-percentage point increase in obesity prevalence (95% CI, 2.4 - 5.9) and lower education level in the head of household was associated with a 9.0-percentage point increase (95% CI, 7.2 - 10.7).

Moreover, the gap in obesity prevalence between adolescents from low-income households was 6.4 percentage points greater (95% CI, 1.5 - 11.4) in 2015 - 2018 compared to 1999 - 2002. A similar trend was noted for education, with 4.2-percentage points greater prevalence (95% CI, -0.8 to 9.3) for individuals with lower head of household education levels in 2015 - 2018 versus 1999 - 2002.

The gap in obesity prevalence by income and education increased by an average of 1.5 (95% CI, 0.4 - 2.6) and 1.1 (95% CI, 0.0 - 2.3) percentage points every 4 years, according to investigators.

“Future studies should assess strategies to reduce socioeconomic disparities in obesity among US adolescents and evaluate their long-term health consequences,” Inoue concluded.

The research letter, “Evaluation of Obesity Trends Among US Adolescents by Socioeconomic Status, 1999 - 2018,” was published in JAMA Pediatrics.