Association Between Sodium Excretion and Cardiovascular Disease and Mortality in the Elderly: A Cohort Study

Abstract

ObjectiveHigh dietary sodium intake is a risk factor for cardiovascular events and death. Recently, a J-shaped correlation between sodium intake and adverse outcomes has been shown. The evidence on the association between sodium intake and cardiovascular outcomes in the elderly is scant. The objective of this study was to evaluate the correlation between sodium intake and cardiovascular events and mortality in an elderly population, taking into account frailty status. DesignCohort study of community dwelling older people enrolled in the InCHIANTI (Invecchiare in Chianti - Aging in the Chianti) study from 1998 to 2000 and followed-up for 9 years. SettingTwo communities in Tuscany, Italy. ParticipantsA total of 920 participants 65 years of age and older, with 24-hour urinary sodium excretion data. MeasurementsNine-year mortality and incident cardiovascular events were analyzed using Cox and nonlinear log-binomial models, stratified by frailty status. Sensitivity analysis in participants without hypertension and cardiovascular diseases was performed. ResultsMean age of the population was 74.5 years (standard deviation 6.99); 55.4% were women. There was a bi-modal association between sodium excretion and mortality, with risk increasing only below sodium excretion of 6.25 g/d [hazard ratio (HR) 1.29, 95% confidence interval (CI) 1.20-1.38], confirmed in the adjusted model (HR 1.12, 95% CI 1.04-1.22). These results were confirmed in participants without cardiovascular diseases. After stratification for frailty phenotype, the association was stronger in frail participants (adjusted HR 1.23, 95% CI 1.02-1.50 vs HR 1.11, 95% CI 1.01-1.22 in robust participants). There was no association between 24-hour sodium excretion and 9-year incidence of cardiovascular diseases (adjusted risk ratio 0.96, 95% CI 0.90-1.02). ConclusionsReduced sodium excretion is associated with increased mortality in a sample of community-dwelling older people, especially among the frail participants. High levels of sodium excretion are not associated with adverse outcomes in this population; therefore, sodium restriction might not be beneficial in older people.