The association between urinary sodium excretion and blood pressure in a community-based population: the Yamagata...

The association between salt intake and blood pressure levels is still inconclusive, and may be influenced by patient characteristics. We thus conducted a community-based cross-sectional study.

This study included 2297 subjects aged ≥ 40 years not on antihypertensive medication at the time of a health check-up. We examined the association between blood pressure levels and the estimated amount of 24-h urinary sodium excretion (e24hUNa) stratified by background characteristics. The 24-h urinary excretion levels of sodium and potassium were estimated from Kawasaki's equation using a spot urine sample.

The association of systolic blood pressure (SBP) and diastolic blood pressure (DBP) with e24hUNa was significantly positive in a multiple linear regression model adjusted for confounders including age, sex, smoking, alcohol consumption, body mass index, diabetes, hypercholesterolemia, renal function, and potassium excretion. The regression coefficients of changes in SBP and DBP per 1 SD increase in e24hUNa (53 mEq/day) were + 1.91 mmHg and + 0.94 mmHg, respectively. In the subgroup analyses, the increase in SBP was especially greater in the elderly, in subjects with diabetes, and in subjects with reduced renal function compared to those in the counterparts. The association between SBP and e24hUNa was insignificant in subjects with eGFR ≥ 90 ml/min/1.73m², while the association with progression of renal dysfunction was stronger and significant.

These results demonstrated that the association between blood pressure and urinary sodium excretion was strengthened by characteristics of subjects such as aging, presence of diabetes, and renal impairment in the community-based population.