Association Between Socioeconomic Status and Incident Sarcopenic Obesity: A 17-Year Prospective Cohort Study

Background: Sarcopenic obesity, defined as the coexistence of low muscle mass and excess adiposity, is an emerging public health concern in aging populations. However, longitudinal evidence on the association between socioeconomic status (SES) and incident sarcopenic obesity remains limited, particularly in Asian populations. This study aimed to investigate the association between SES and the long-term incidence of sarcopenic obesity in a large Korean cohort. Methods: We conducted a prospective cohort study using data from the Korean Genome and Epidemiology Study (KoGES). Community-dwelling adults aged ≥ 40 years without sarcopenic obesity at baseline were followed for a mean of 17 years. Sarcopenic obesity was defined as low body mass index (BMI)-adjusted skeletal muscle mass (sex-specific lowest 20th percentile) combined with obesity (BMI ≥ 25 kg/m²). SES indicators included educational attainment, household income, and marital status. Kaplan-Meier methods were used to estimate cumulative incidence, and Cox proportional hazards models were applied to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) with sequential adjustment for demographic, lifestyle, and metabolic factors. Results: In the fully adjusted model, participants with elementary school education showed a higher hazard ratio of incident sarcopenic obesity compared with those with college education or higher (HR 1.39; 95% CI 1.11-1.73; p = 0.003). Similarly, individuals with a household income < 1.0 million KRW per month had a higher hazard ratio compared with those earning ≥4.0 million KRW (HR 1.31; 95% CI 1.02-1.70; p = 0.037). Unmarried participants also showed a higher hazard ratio compared with married individuals (HR 1.31; 95% CI 1.09-1.57; p = 0.003). Conclusions: Lower SES was independently associated with a higher incidence of sarcopenic obesity over long-term follow-up in this population-based cohort. These findings highlight the importance of considering socioeconomic factors in the prevention of sarcopenic obesity.