[Associations between 24-hour urinary sodium excretion and all-cause mortality in adults living in north China]

Objective: To investigate the associations between 24-hour urinary sodium excretion (24hUNaE) and all-cause mortality in adult Northern Chinese population. Methods: Data from this study were derived from the prospective urban and rural epidemiology (PURE) study in north China. Baseline information of all participants were obtained by face to face interview through trained research staffs based on questionnaires, and morning fasting urine samples of participants were collected to estimate 24hUNaE and 24-hour potassium excretion (24hUKE). Multivariable frailty Cox regression models were used to explore the association between 24hUNaE (<3.00, 3.00-3.99, 4.00-4.99, 5.00-5.99 and ≥6 g/d) and all-cause death. Results: A total of 27 310 participants were included in this study. The mean 24hUNaE was (5.84±1.73) g/d. After a median follow-up of 8.8 years, 1 024 participants died (3.7%), including 390 cardiovascular related deaths and 591 non-cardiovascular related deaths. The cause of death of the remaining patients could not be determined. Using 24hUNaE level of 4.00-4.99 g/d as the reference group, after fully adjustment, 24hUNaE ≥6.00 g/d was associated with an increased risk of all-cause death (HR=1.24, 95%CI: 1.02-1.49) and cardiovascular related death (HR=1.39, 95%CI: 1.02-1.88). 24hUNaE<3.00 g/d was associated with increased risk of all-cause mortality (HR=1.38, 95%CI: 0.96-1.99). There was no significant association between 24hUNaE and non-cardiovascular related death. Furthermore, using the combination of 24hUNaE 4.00-4.99 g/d and 24hUKE≥2.11 g/d as the reference group, the highest risk occurred in participants with the combination of low sodium (<3.00 g/d) and low potassium (<2.11 g/d). Conclusion: 24hUNaE equal or higher than 6 g/d or lower than 3 g/d is associated with increased risk of all-cause mortality and cardiovascular related death in Northern Chinese population. Besides, moderate sodium intake in combination with increased potassium intake might reduce the risk of all-cause death.