Fig. 1.

Middle-age serum sodium and risk of all-cause mortality in Atherosclerosis Risk in Communities (ARIC) study. a) Overview of ARIC study and exclusion criteria. b, c, d) Splitting study participants into four groups using classification and regression trees (CART) algorithm based on average serum sodium measured at visits 1 and 2 and cumulative mortality by the end of 25 years follow-up. b) Overview of CART algorithm outcome for the group splitting. c) Histograms showing distributions of the study participants according to serum sodium. Groups identified by CART algorithm are shown in different colors. Mortality rate by the end of 25 years follow-up and number of people in each group are shown above histogram. d) Average age does not differ between sodium groups. e, f) Assessment of relative risk for all-cause mortality in four sodium groups. e) Kaplan–Meier Survival Analysis: P < 0.001 (Log–Rank test). All Pairwise Multiple Comparison Procedures): ∗P = 0.04, ∗∗P = 0.001 (Holm-Sidak method). See Table S2 for N at risk at each time point. f) Time-to-event analysis: COX proportional hazard model. People whose middle-age serum sodium exceeds 144 mmol/l or is lower than 137 mmol/l have increased risk of dying at earlier age. See also Table S2 for descriptive statistics and demographic data for these four sodium groups.