A population study on the relationship between blood pressure and the excretion of urinary cations.

The relationships between blood pressure and the 24-h excretion of three urinary cations (Ca2+, K+, and Na+) were investigated in a random sample of 528 adults (greater than or equal to 20 years) inhabitants of two Belgian towns. In these adults both systolic and diastolic blood pressures were strongly and independently correlated with age and body weight. Systolic pressure in women was significantly and positively related to pulse rate. After adjusting for age and body weight, systolic and diastolic pressures in men were significantly (p less than 0.001 and p less than 0.01, respectively) and negatively correlated with urinary potassium excretion. Diastolic pressure in men was weakly (p less than 0.05 after adjusting for body weight, age, and urinary potassium excretion) but positively correlated with calcium excretion. In a subsample of 162 premenopausal women, blood pressure was higher in current contraceptive pill users than in women not taking oral contraceptives. In 56 current pill users there was a positive association between systolic pressure and 24-h urinary sodium (p less than 0.01 after adjusting for age, body weight, and pulse rate). The present study indicates that urinary potassium is a consistent and negative predictor of both systolic and diastolic pressures in adult men, whose diastolic pressure is weakly and positively associated with urinary calcium. The positive association between systolic pressure and urinary sodium in current users of contraceptive pills may suggest that their blood pressure becomes responsive to their usual salt intake.