Abstract Body: Introduction
High sodium intake increases risks of hypertension (HTN) and mortality, but the impact of very low sodium intake is uncertain. No studies have examined dietary sodium as low as those in the original Rice Diet (RD: ~200 mg/d sodium, ~5% calories each from protein and fat). We retrospectively assessed factors associated with systolic blood pressure (SBP) change and survival of RD-treated patients across BP categories.

Methods
We identified 12,312 adults (1942-1994) who consumed the RD for ≥7 days. Urinary chloride (UCl≤42mg/dl) indicated diet adherence. Multivariable linear regression examined factors linked with SBP change. Actuarial survival analysis compared survival by BP groups. Cox proportional hazards model assessed factors influencing survival. Observed and predicted life expectancy was compared using US Social Security Administration (SSA) life-tables. Significance was defined as p<0.05.

Results
Patients were mostly female (64.8%), median age 48 [34,57] years, BMI 32.9 [0.1, 38.5] kg/m². SBP declined rapidly during the first 4 weeks (Figure 1) and remained stable to week 52. Greater 12-week SBP reduction was associated with higher baseline SBP (β[95%CI]:-0.57[-0.59,-0.55]), better diet adherence(-0.05[-0.07,-0.04]), and greater weight loss(-0.42[-0.53,-0.31]); smaller reductions were linked to older age(0.1[0.07,0.14]) and worse kidney function(0.13[0.08,0.19]). Across BP groups, baseline SBP consistently predicted SBP decline.

Survival (Figure 2) was longest in the normal BP group, followed by elevated and stage 1 HTN, which were similar, and markedly less in stage 2 and severe HTN. A larger first-month SBP reduction was strongly and progressively associated with improved survival (Table). Older age, male sex, worse kidney function, and higher baseline SBP increased mortality risk; higher BMI and better diet adherence were protective. Mortality risk was most influenced by male sex and early SBP reduction. Compared with SSA life tables, RD patients with normal, elevated, stage 1 and stage 2 HTN lived 4.1, 5.0, 3.7 and 1.0 yrs longer, respectively, whereas those with severe HTN lived 11 yrs less.

Conclusions
The RD was associated with lowered SBP and improved survival. SBP reduction and survival benefits were comparable in elevated and stage 1 HTN, with benefit even in the normal BP group. Survival improved proportionally to the magnitude of SBP reduction, underscoring the strong impact of intensive diet intervention on BP and mortality.