Dietary sodium intake and prediabetes in Korean adults: a nationally representative cross-sectional analysis of 57,165 participants (KNHANES 2010–2018)

BACKGROUND: Although high sodium intake is a well-established risk factor for cardiovascular disease, its specific association with prediabetes remains unclear, particularly, in Asian populations. We aimed to investigate the association between dietary sodium intake and prediabetes prevalence in a large-scale Korean cohort. METHODS: This cross-sectional study analyzed 57,165 adults without diabetes from the Korea National Health and Nutrition Examination Survey 2010-2018. Dietary sodium was assessed via a 24-h recall. We evaluated associations using multivariable-adjusted odds ratios (ORs) across sodium octiles and the World Health Organization (WHO) threshold (≥2.0 g/day, salt ≥5.1 g/day). Restricted cubic splines (RCS) were used to characterize dose-response patterns. RESULTS: Prediabetes prevalence rose from 22.9% in the lowest sodium octile (≤1.4 g/day) to 33.3% in the highest (>6.2 g/day). Using the WHO threshold, sodium intake ≥2.0 g/day was associated with greater odds of prediabetes (crude OR 1.417, 95% CI 1.357-1.479; p < 0.001), which remained significant after adjustment for age, sex, body mass index, and clinical risks (hypertension, dyslipidemia, stroke, myocardial infarction, angina pectoris, renal failure, thyroid disease, cancer, and current smoking) (OR 1.151, 95% confidence interval [CI] 1.093-1.212; p < 0.001). RCS analysis identified a significant non-linear dose-response pattern (p-nonlinearity <0.01), where risk peaked at approximately 3-4 g/day of sodium (7.6-10.2 g/day salt). Sensitivity analysis showed this association was independent of potassium intake (R = 0.63). Subgroup analysis by body mass index revealed divergent patterns, with a nearly linear increase in the underweight group and a U-shaped trend in the overweight group. Annual trends (2010-2018) showed a significant decline in median sodium intake from 3.8 g/day to 2.7 g/day (p-trend <0.001). CONCLUSION: Higher dietary sodium intake is independently associated with an increased prevalence of prediabetes in Korean adults. The observed risk threshold and dose-response plateau suggest that sodium moderation, specifically, aiming below the 3-4 g/day range, may be a vital strategy for preventing glycemic dysregulation alongside blood pressure control.