High Estimated 24-Hour Urinary Sodium Excretion is Associated With Metabolic Syndrome and Its Phenotypes: Tehran Lipid and Glucose Study.

Abstract

Aim: This study aimed to investigate the association between estimated 24-h urinary sodium (24 h-UNa) excretion and metabolic syndrome (MetS) prevalence and its components in adults.

Methods: This cross-sectional study (2015-2017) included 2057 men and women (mean age: 45.5 ± 14.8 years; 45.5% men). Anthropometric assessments and biochemical measurements were conducted according to standard protocols. Na intake was estimated from second-void morning urine specimens using the Tanaka formula, which incorporates spot UNa, potassium (UK), and creatinine (UCr) levels. MetS was defined based on the National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) criteria, encompassing hyperglycemia (G), hypertriglyceridemia (T), low high-density lipoprotein cholesterol (HDL-C) (H), hypertension (B), and abdominal obesity (W). Multivariable logistic regression, adjusted for age, sex, estimated glomerular filtration rate (eGFR), physical activity level (PAL), and smoking status, was employed to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for MetS and its components across tertiles of 24 h-UNa (< 124, 124-162, and ≥ 162 mmol/day).

Results: The overall MetS prevalence was 37.6%, with a mean estimated 24 h-UNa excretion of 3491 ± 1020 mg/day. After multivariable adjustment, high UNa excretion was independently associated with increased odds of MetS (OR = 1.49, 95% CI = 1.16-1.92), abdominal obesity (OR = 2.70, 95% CI = 2.09-3.49), and hypertriglyceridemia (OR = 1.48, 95% CI = 1.16-1.89). However, no significant association was observed between high UNa excretion and hypertension (OR = 1.13, 95% CI = 0.86-1.48). Furthermore, the prevalence of specific MetS phenotypes was significantly elevated in the highest compared to the lowest 24 h-UNa tertile (e.g., WBH [13.3% vs. 11.1%, p = 0.018], WBT [18.5% vs. 14.1%, p = 0.033], BHT [11.3% vs. 10.5%, p = 0.028], WHT [22.1% vs. 17.7%, p = 0.006], and WBHT [10.4% vs. 9.3%, p = 0.019]).

Conclusion: Elevated estimated 24 h-UNa excretion is independently associated with a higher likelihood of MetS and its key components, particularly abdominal obesity and hypertriglyceridemia. These findings suggest that high dietary Na intake may be an independent risk factor for MetS, and that dietary salt reduction could play a vital role in the primary prevention of MetS.