Age-dependent increase in blood pressure in two different Native American communities in Brazil

Cardiovascular risk factors were surveyed in two Indian populations (Guarani, n = 60; Tupinikin, n = 496) and in a non-Indian group (n = 114) living in the same reserve in southeast Brazilian coast. The relationship between an age dependent blood pressure (BP) increase with salt consumption was also investigated.

Overnight (12 h) urine was collected to evaluate Na excretion. Fasting glucose and lipids, anthropometry, BP, ECG and carotid-femoral pulse wave velocity (PWV) were measured in a clinic visit. Participation (318 men/352 women, age 20-94 years; mean = 37.6 +/- 14.9 years) comprised 80% of the eligible population.

The prevalence of hypertension, diabetes and high cholesterol was similar in Tupinikins and in non-Indians and higher than in Guaranis. The prevalence of smoking and obesity was higher in the latter group. Hypertension and diabetes were detected in only one individual of the Guarani group. Mean BP adjusted to age and BMI was significantly lower (P<0.01) in Guaranis (82.8 +/- 1.6mmHg) than in Tupinikins (92.3 +/- 0.5mmHg) and non-Indians (91.6 +/- 1.1 mmHg). Urinary Na excretion (mEq/12h), however, was similar in the three groups (Guarani = 94 +/- 40; Tupinikin = 105 +/- 56; non- Indian = 109 +/- 55; P>0.05). PWV (m/s) was lower (P<0.01) in Guarani (7.5 +/- 1.4) than in Tupinikins (8.8 +/- 2.2) and non-Indians (8.4 +/- 2.0). Multiple regression analysis showed that age and waist-to-hip ratio (WHR) were independent predictors of SBP and DBP (r(2) = 0.44) in Tupinikins, whereas the WHR was the unique independent predictor of BP variability in Guaranis (r(2) = 0.22).

Lower BP levels in Guaranis cannot be explained by low salt intake observed in other primitive populations.