Trends and inequalities in overall and abdominal obesity by sociodemographic factors in Korean adults, 1998–2018

Few studies have comprehensively examined the nationwide trends in overall and abdominal obesity prevalence and related sociodemographic inequalities in Korea. In the Korea National Health and Nutrition Examination Survey 1998–2018, we estimated the age-standardized prevalence of overall (body mass index ≥ 25 kg/m²) and abdominal obesity (waist circumference ≥ 90 cm men, ≥85 cm women) in each sociodemographic subgroup of Korean adults (aged 19–79 years). For each survey year, weighted logistic regression was performed to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the associations between obesity prevalence and soci-odemographic factors. During the study period, the prevalence of overall and abdominal obesity increased in men (24.8% to 42.4%; 20.1% to 32.1%; respectively) but only a small change was observed in women (26.5% to 26.0%; 22.7% to 20.9%; respectively). Obesity prevalence increased in all sociodemographic groups of men but varied across groups in women. In women, income (4^th vs. 1^st quartiles in 2016–2018: OR (95% CI) = 0.66 (0.56–0.78) overall obesity; 0.60 (0.51–0.71) abdominal obesity) and education (college or higher vs. high school or less: 0.62 (0.54–0.72) overall obesity; 0.58 (0.50–0.68) abdominal obesity) were inversely associated with obesity prevalence, and the gaps be-came more pronounced since 2007. Our data suggest that the inequalities in obesity prevalence by sex and by socioeconomic status have become more apparent over time in Korea.