Serum Sodium Levels, Their Related Factors, and Association with All-Cause and Cardiovascular Mortality in Community-Dwelling Adults

Background: Abnormal serum sodium levels can result from a wide array of physical conditions and are well-known risk factors for death in hospitalized patients. However, little is known about such associations in community-dwelling adults. Methods: A prospective cohort study conducted in Japan involved 7,178 community-dwelling adults (age 40–97 years; 50.1% women). We divided serum sodium levels at <140 (low), 140–142 (reference), and ≥143 (high) mmol/L. We explored factors related to serum sodium levels using multinomial logistic regression analysis and the association of serum sodium levels with all-cause and cardiovascular mortality, using Cox proportional hazards model. Results: Median serum sodium level at baseline was 141 mmol/L. Factors related to a low serum sodium level were male sex, eGFR <60mL/min/1.73m2, and diabetes. Factors related to a high serum sodium level were older age, drinking habit, and high body mass index. During a median follow-up of 8 years, 703 events occurred. Compared with the reference, a low serum sodium level was associated with a higher risk of all-cause and cardiovascular mortality (adjusted hazard ratio [95%CI] 1.48 [1.23, 1.78] and 1.77 [1.24, 2.54], respectively). When modeled with restricted cubic splines, the associations formed a U-shape, with a serum sodium level of 141 mmol/L having the lowest risk (Figure). Conclusion: Demographic factors, kidney function, and diabetic status were correlated with serum sodium levels. The findings of this study indicate that even community-dwelling adults with low-normal serum sodium levels are at high risk of all-cause and cardiovascular mortality. Funding: Government Support – Non-U.S.Figure. Association of serum sodium levels with all-cause and cardiovascular mortality