Relationship of urinary sodium and sodium‐to‐potassium ratio to blood pressure in older adults in Australia

Abstract

To assess the relationship between dietary sodium intake, as measured by urinary electrolyte excretion, and blood pressure within a population of older Australian adults. A cross-sectional study of adults enrolled in the Melbourne Collaborative Cohort Study, stratified by sex, country of birth (Italy, Greece, Australia/New Zealand) and age (50-59and 60-75years). Blood pressure measurements were taken in 2003-2007and 24-hour urine collections in 2007-2008. 24-hour urinary excretion of sodium and potassium, urinary sodium-to-potassium ratio, and clinic blood pressure measurement. The mean ± SD age of 783participants was 64.0± 6.3years. Mean ± SD urinary sodium was 155.1± 63.1mmol/day (8.9± 3.6g salt/day), urinary potassium was 82.3± 27.9mmol/day, and urinary sodium-to-potassium ratio was 1.99± 0.83. In the 587participants with blood pressure measurements, urinary sodium and the sodium-to-potassium ratio were both associated with systolic blood pressure in all adjusted and unadjusted models (mmHg change per 100mmol/day increase in sodium: regression coefficient, 2.3, 95% CI, 0.1-4.6; P=0.049, adjusted for age, sex, body mass index, country of birth and antihypertensive medication use). This study has demonstrated, for the first time within an Australian population sample of older adults, that sodium intake is positively associated with blood pressure. These results suggest that a population-wide reduction in sodium intake could be effective in reducing blood pressure in adults in Australia.