Differential impacts of 24 hour urinary sodium excretion on cardiovascular diseases or cancer mortality in a general population.

Background: Elevated blood pressure is a major risk factor for cardiovascular (CV) disease. But the effects of sodium intake or excretion on CV mortality are uncertain. The present study aimed to investigate the association between 24 h urinary sodium excretion, as a marker of dietary salt intake, and CV or cancer mortality in a healthy Japanese population using 24 hurine collection.

Methods: The baseline study was conducted in 1980. A total of 1291 participants aged 21 to 85 years, underwent health check-ups, which included blood chemistry measurements and the collection of 24 h urine samples. Enrolled 1291 participants were followed up for 27.5 years, in whom the final follow-up rate was 95.8%. Cox proportional hazards regression models were used to assess the association between 24 h urinary sodium excretion and CV or cancer mortality.

Results: The mean 24 h urinary sodium excretion was 5.80 ± 2.28 g/day. There were 631 deaths: 153 (27%) from cancer, 142 (26%) from CV disease. In the Cox proportional hazard regression model after adjustment for confounding factors, systolic and diastolic blood pressures, and uric acid were positively associated with CV mortality, and the 24 h urinary sodium and potassium excretions were inversely associated with CV mortality (p < 0.05). On the other hand, there were no association between 24 h urinary sodium excretions and cancer mortality. We divided the urinary sodium excretions levels into quartiles. After adjustment for confounding factors, the hazard ratio of CV mortality in the highest quartile of 24 h urinary sodium excretion versus the lowest was 0.46 (p < 0.05). The cumulative survival rate for CV death was significantly decreased in the lowest quartile compared with the other higher groups.

Conclusions: We found that impacts of 24 h sodium excretion on CV and cancer mortalities were much different in the general population.