Are 24 h urinary sodium excretion and sodium:potassium independently associated with obesity in Chinese adults?

Objective: To examine the association of 24 h urinary Na excretion and Na:K with obesity in Chinese adults. Design: Population-based cross-sectional study using a four-stage stratified sampling strategy. Setting: Shandong Province, China. Subjects: Chinese adults (n 1906) aged 18-69 years who provided complete 24 h urine samples. Results: Odds of obesity increased significantly across increasing quartiles of urinary Na excretion (1.00, 1.54, 1.69 and 2.52, respectively, for overweight; 1.00, 1.20, 1.50, and 2.03, respectively, for obesity; 1.00, 1.44, 1.85 and 2.53, respectively, for abdominal obesity (assessed by waist circumference); and 1.00, 1.28, 1.44 and 1.75, respectively, for abdominal obesity (assessed by waist-to-height ratio); P for linear trend <0.001 for all). In addition, odds of abdominal obesity, but not odds of overweight and obesity, increased significantly with successive Na:K quartiles. Additionally, for each increment in urinary Na excretion of 100 mmol, odds of overweight, obesity, abdominal obesity (by waist circumference) and abdominal obesity (by waist-to-height ratio) increased significantly by 46 %, 39 %, 55 % and 33 %, respectively. Similarly, with a 1 sd increase in Na:K, odds of abdominal obesity (by waist circumference) and abdominal obesity (by waist-to-height ratio) increased significantly by 12 % and 15 %, respectively. Conclusions: These findings suggest that 24 h urinary Na excretion and Na:K might be important risk factors for obesity in Chinese adults.