Association of the urinary sodium to urinary specific gravity ratio with metabolic syndrome in Korean children and adolescents: The Korea National Health and Nutrition Examination Survey 2010-2013

OBJECTIVES This study aimed to evaluate the association between sodium intake and metabolic syndrome (MetS) in Korean boys. METHODS A total of 1,738 boys aged 10-18 years were included in this study from the Korea National Health and Nutrition Examination Survey (KNHANES) during the years 2010-2013. Sodium intake was assessed using the urinary sodium excretion to urinary specific gravity ratio (U-Na to U-SG ratio). RESULTS The median U-Na to U-SG ratio was 133.27 mmol/L (interquartile range: 95.66-178.50 mmol/L). Significant positive associations were found between the U-Na to U-SG ratio and the TG (P = 0.001 for trend) and TG concentrations, and these concentrations were significantly higher in boys with a U-Na to U-SG ratio in the highest quartile compared with those with a ratio in the lowest (P = 0.001) and second (P = 0.033) quartiles, as demonstrated through analysis of covariance (ANCOVA) after adjustment for possible confounders, including age, BMI standard deviation score, ferritin, vitamin D, house income, smoking, alcohol intake, physical activity, season, total intake, total energy intake, protein intake, fat intake, carbohydrate intake, and water intake. Significant inverse associations were found for the U-Na to U-SG ratio with the HDL-C (P = 0.033 for trend) and HDL-C levels, and these values were significantly lower in boys with a ratio in the highest quartile compared with those with a ratio in the second quartile (P = 0.020), as demonstrated through an ANCOVA. Although the trends did not reach statistical significance, a higher U-Na to U-SG ratio tended to be associated with higher SBP (P = 0.086 for trend), DBP (P = 0.063 for trend), and glucose levels (P = 0.099 for trend), as illustrated through ANCOVA. Boys with a ratio in the highest quartile exhibited a 1.73-fold increased risk for elevated TG (95% CI, 1.19-2.51) and a 2.66-fold increased risk for MetS (95% CI, 1.11-6.35) compared with those with a ratio in the lowest quartile, as demonstrated through multivariate logistic regression analyses after adjusting for confounders. CONCLUSIONS Our results suggest that high sodium intake may be significantly independently associated with MetS in Korean boys aged 10-18 years.