Factors associated with 24-hour urinary volume: the Swiss salt survey.

BACKGROUND: Low 24-hour urine volume (24 UV) may be a significant risk factor for decline in kidney function. We therefore aimed to study associated markers and possible determinants of 24 UV in a sample of the Swiss population. METHODS: The cross-sectional Swiss Salt Study included a population-based sample of 1535 (746 men and 789 women) individuals from three linguistic regions of Switzerland. Data from 1300 subjects were available for the present analysis. 24 UV was measured using 24-hour urine collection. Determinants of 24 UV were identified using multivariable linear regression models. RESULTS: In bivariate analysis, 24 UV was higher in women compared to men (2000 ml/24 h [interquartile range (IQR): 1354, 2562] versus 1780 ml/24 h [IQR: 1244, 2360], p = 0.002). In multivariable regression analyses, independent associated markers of 24 UV were female sex (ß = 280, 95% confidence interval [CI]: 174, 386, p < 0.0001), fluid intake (ß = 604, 95% CI: 539, 670, p < 0.0001), sodium excretion (ß = 4.2, 95% CI: 3.4, 4.9, p < 0.0001) age (ß = 6.6, CI: 3.4, 9.7, p < .0001), creatinine clearance (ß = 2.4, CI: 0.2, 4.6, p = 0.04), living in the German-speaking part of Switzerland (ß = 124, CI: 29, 219, p = 0.01), alcohol consumption (ß = 41, CI: 9, 73, p = 0.01 for increasing categories of alcohol consumption), body mass index (ß = -32, CI: -45, -18, p < 0.0001), current smoking (ß = -146, CI: -265, -26, p = 0.02), and consumption of meat and cold cut (ß = -56, CI: -108, -5, p = 0.03). CONCLUSION: In this large population-based, cross-sectional study, we found several strong and independent correlates for 24 UV. These findings may be important to improve our understanding in the development of chronic kidney disease.