SALT INTAKE AND BLOOD-PRESSURE IN RURAL AND METROPOLITAN MEXICO

A selected group of 155 Mexican adults aged 20 - 64 years were studied to investigate the role of sodium (Na) intake in explaining blood pre ssure (BP) differences in a rural town and urban Mexico City. The subj ects had their BP, height, weight and skinfolds measured and they coll ected 3 continuous 24 h urines. Adjusted for age differences, average BPs were significantly higher (p <.05) for the urban (112.7 systolic: 73.6 diastolic mmHg) than for the rural group (108.4 systolic: 70.8 di astolic mmHg). They were also higher for men (111.8 systolic: 74.3 dia stolic mmHg) than for women (109.6 systolic: 70.2 diastolic mmHg), the diastolic BP difference being significant (p <0.05). The average dail y Na excretion was also higher in the urban (122.2 mmol/day) than in t he rural community (98.0 mmol/day) (p <0.01). Potassium excretion rate s showed similar differences. The differences in sodium excretion and blood pressure among communities were particularly marked in those ove r 30 years of age. The means for the four community-sex groups had the same rank order for both BP and Na. However, although some large surv eys have suggested that half the observed differences in BP might be e xplained by different Na intakes, in this study the relationship betwe en Na excretion and BP did not achieve statistical significance. Diffe rences in the body mass index (BMI) accounted for 41% of the observed variance in BP.