Sodium, potassium, body mass, alcohol and blood pressure: the INTERSALT Study. The INTERSALT Co-operative Research Group.

INTERSALT is a multicentre epidemiological study of electrolyte excretion and blood pressure. The 10,079 participants, aged 20-59 years, were sampled from 52 centres around the world, and data were collected according to a strict protocol and with extensive quality control. The relationships between blood pressure and 24-h urinary sodium and potassium excretion, body mass index and alcohol intake were assessed both in individuals and across centres. The individual analyses, with adjustment for confounding variables, showed highly significant positive associations between blood pressure and sodium excretion, the sodium/potassium ratio, body mass index and high alcohol intake, and a significant negative association between blood pressure and potassium excretion. In the inter-centre analyses, sodium was significantly related to the slope of blood pressure with age, but not to median blood pressure. Other intercentre results were inconsistent.