Health literacy and metabolic syndrome in Korean adults: a nationwide cross-sectional analysis of KNHANES 2023–2024

Health literacy (HL) is a social determinant of health, yet its independent, population-level association with metabolic syndrome (MetS) remains unclear, particularly in Asian populations. Using data from the first Korea National Health and Nutrition Examination Survey cycles to include a validated, multidimensional HL instrument, we examined the association between HL and MetS, including variation by sex and associations with individual MetS components. We performed a nationally representative cross-sectional analysis of 11,142 adults using the 2023–2024 Korea National Health and Nutrition Examination Survey, applying complex survey weights. HL was measured using a validated 10-item instrument (range, 10–40); a score ≥ 30 was considered adequate. MetS was defined using harmonized criteria. We used sequential logistic regression, with age and sex adjustment followed by socioeconomic adjustment as the primary model, and conducted sensitivity analyses additionally adjusting for lifestyle factors and body mass index (BMI). Restricted cubic splines and prespecified subgroup and domain-specific analyses were also performed. Prevalence ratios were estimated using survey-weighted modified Poisson regression. The weighted prevalence of MetS was 31.1%. In the primary model, adequate HL was inversely associated with MetS after adjustment for sociodemographic factors (prevalence ratio, 0.903; 95% CI, 0.848–0.962; P = 0.002; OR, 0.843). The association persisted after additional adjustment for lifestyle factors (PR, 0.917; 95% CI, 0.859–0.978) and was modestly attenuated after BMI adjustment (PR, 0.928; 95% CI, 0.874–0.986). An exploratory restricted cubic spline suggested a nonlinear pattern that was not significant under a design-based test ( P = 0.084). The association differed by sex ( P for interaction < 0.001) and was observed in women but not in men. Domain- and component-specific findings were exploratory; the four HL domains were highly intercorrelated and not distinguishable in mutually adjusted models. In Korean adults, adequate HL was inversely associated with prevalent MetS. The stronger association observed in women warrants prospective confirmation. Although separate exploratory models suggested inverse associations for the Healthcare and Technology & Resources domains, these domains were highly intercorrelated and not distinguishable in mutually adjusted analyses.