Abstract 248: Assessing the Long Term Association Between Sodium Intake and Mortality
Background: Studies linking sodium intake and mortality have produced conflicting results, with some showing an inverse or J-shaped relationship. An earlier assessment of this population (mean 3.8 years follow-up) revealed an inverse association of sodium to CVD morbidity and mortality. We now report the association with all-cause and cardiovascular mortality during an average 18.4 years of follow-up.
METHODS: Subjects participated in a worksite hypertension program between 1980-1995. Entry criteria were SBP≥140, DBP≥90, or receiving antihypertensive medications. Sodium intake was assessed with 24-hour urine collection. Antihypertensives were discontinued 3-4 weeks prior to collection, and individuals with BP <140/90 after washout were excluded. Mortality data through August 2009 were obtained from NDI and SS Master Death Files. Unadjusted and adjusted hazard ratios (HR) for sex-specific sodium quartiles with all-cause and CV mortality were calculated using Cox regressions.
Results: Of 2983 individuals, 66% were male; mean(±sd) age 52.2 (±9.5) years; mean sodium intake 3023 (±1584) mg/day. Mean follow-up time was 18.4 (±5.9) years. There were 878 deaths, including 351 (40%) due to cardiovascular causes. HR and 95% CI (QI vs QIV) for all-cause and CV mortality respectively were 1.24 (1.02, 1.49), p=0.03 and 1.68 (1.20, 2.35), p=0.003 in unadjusted models, and 0.76 (0.61, 0.95), p=0.02, and 0.86 (0.60, 1.25), p=0.44 in adjusted models. Subgroup analysis limited to MI, heart failure and ischemic heart disease also revealed a non-significant direct relationship (p=0.15).
Conclusions: We observed a direct association between sodium intake and all-cause mortality, and a similar but non-significant trend with cardiovascular mortality. These are in contrast both to unadjusted models and to an earlier study in the same population. Absence of clinical information after 1998, and the gap between sodium determination and follow-up, limits ability to explain these contrasting findings. Studies that obtain prolonged information on dietary intake and clinical experience over time will be required to better assess long-term associations between sodium intake and health outcomes.
- © 2012 by American Heart Association, Inc.