Electrolytes are associated with blood pressure at old age: the Rotterdam Study.

We examined the association of urinary sodium and potassium excretion with blood pressure (BP) in the Rotterdam Study, a population-based study among 7983 men and women aged 55 and over. The present analysis included 1006 subjects with complete BP and urinary data who did not use antihypertensive drugs and did not report themselves to be hypertensive. Electrolyte excretions were assessed in a timed nocturnal urine sample and standardized to 24-h values. The association of electrolyte excretions with BP was studied in a multiple linear regression model with adjustment for age, sex, and body mass index. When sodium and potassium were entered simultaneously into the multivariate model, a 100 mmol increase in potassium was associated with a 9.4 decrease in systolic (P = 0.01) and a 4.9 mm Hg decrease in diastolic BP (P = 0.01). Sodium was directly related to BP, with a 2.2 mm Hg increase in systolic (P = 0.06) and a 0.8 mm Hg increase in diastolic BP (P = 0.14) per 100 mmol. Our findings suggest that an increased intake of potassium and a decrease intake of salt may lower BP at old age.