Diastolic pressure as an index of salt sensitivity.

This paper analyses the association between blood pressure and sodium excretion in 3975 individuals aged 20-74 years, selected in a probability sample survey of private households carried out in Rio Grande do Sul, Brazil. Sodium and creatinine titrations were performed in casual urine samples collected at the time of BP measurements. A subsample of 611 subjects provided 24 h urine collections. The regression slopes of systolic pressure on sodium excretion increased when diastolic level was higher. At the lowest levels of diastolic pressure the slope did not differ significantly from zero. The adjusted correlation coefficient then rose progressively to a maximum of +0.41 at diastolic pressures of 95-99 mmHg. Strikingly, at diastolic pressures of > or = 100 mmHg, there was no longer any significant association between systolic pressure and sodium excretion. These results could explain some earlier contradictory findings concerning the role of salt intake in hypertension and provide estimates of expected reduction on the prevalence of hypertension in each diastolic pressure group following a reduction on salt intake of a population.