The reasons for the inconsistent association between salt consumption and blood pressure levels observed in within-society surveys are not known. A total of 157 normotensive subjects aged 18 to 35 years, selected at random in a cross-sectional population-based survey, answered a structured questionnaire. They were classified as strongly predisposed to hypertension when two or more first-degree relatives had a diagnosis of hypertension. Anthropometric parameters were obtained and sitting blood pressure was determined with aneroid sphygmomanometers. Sodium and potassium excretion was measured by flame spectrophotometry in an overnight urine sample. A positive correlation between blood pressure and urinary sodium excretion was detected only in the group of individuals strongly predisposed to hypertension, both for systolic blood pressure (r = 0.51, P<0.01) and diastolic blood pressure (r = 0.50, P<0.01). In a covariance analysis, after controlling for age, skin color and body mass index, individuals strongly predisposed to hypertension who excreted amounts of sodium above the median of the entire sample had higher systolic and diastolic blood pressure than subjects classified into the remaining conditions. The influence of familial predisposition to hypertension on the association between salt intake and blood pressure may be an additional explanation for the weak association between urinary sodium excretion and blood pressure observed in within-population studies, since it can influence the association between salt consumption and blood pressure in some but not all inhabitants.

Diversos comitês normativos em hipertensão arterial recomendam considerar a média de várias aferições da pressão arterial com esfigmomanômetro para diagnosticar hipertensão. Não há consenso sobre o número de medidas a serem consideradas. OBJETIVO. Descrever o comportamento da pressão arterial obtida em três dias diferentes, utilizando-se a média de seis aferições para o diagnóstico de hipertensão. MÉTODOS. No ambulatório de hipertensão da Unidade de Farmacologia Clínica do Hospital de Clínicas de Porto Alegre, emprega-se a média de seis determinações, obtidas em três dias diferentes, para diagnosticar e classificar a hipertensão, exceto nos pacientes com valores muito baixos ou elevados nas duas primeiras aferições. Cinqüenta e oito pacientes foram submetidos a essa rotina. RESULTADOS. As médias das pressões sistólica (PS) e diastólica (PD) decresceram da primeira à sexta determinação (ANOVA para medidas repetidas: F = 4,45, p = 0,001 para PS e F = 5,54, p < 0,001 para PD). Os pacientes foram divididos em grupos com PS e PD obtidas na primeira aferição superiores e inferiores à média de todo grupo. A diminuição de ambas as pressões ao longo das seis aferições ficou restrita aos grupos com valores da primeira determinação superiores à média de todo o grupo (ANOVA: F = 8.03; p < 0,0001 para PS e F = 6,33, p <0,0001 para PD). A regressão à média e uma reação de alerta inicial são explicações aventadas para esse fenômeno. CONCLUSÃO. Esses dados demonstram que o diagnóstico de hipertensão arterial não deve ser feito com base em uma única aferição e sugerem que a recomendação de diagnosticar hipertensão severa baseando-se em altos valores das duas primeiras medidas pode classificar erroneamente alguns pacientes.

It has been recommended to take the average of several blood pressure (BP) determinations with a sphygmomanometer to diagnose hypertension, but there is no agreement on the reading numbers. PURPOSE. Describing the behavior of BP readings taken in three different days to establish the classificatory BP in an outpatient hypertension clinic. METHOD. In the outpatient hypertension clinic of the Clinical Pharmacology Division of the Hospital de Clínicas de Porto Alegre, we use the mean of six readings taken in three different days to establish the classificatory blood pressure, except for those with very high or low values in the first day. In this report we describe the behavior of BP in 58 patients submitted to this routine. RESULTS. The mean of systolic (SBP) and diastolic (DBP) blood pressures decreased from the first to the 6th reading (ANOVA for repeated measurements: F = 4.45, P = 0.001 for SBP and F = 5.54, P < 0.001 for DBP). Afterward, the patients were classified into two groups according their first SBP and DBP reading. The decreasing in both SBP and DBP was confined to those with the first measurement in the upper half of the entire group (ANOVA: F = 8.03; P < 0.0001 for SBP and F = 6.33, P <0.0001 for DBP). Regression to the mean and some reactiveness in the first day are possible explanations for this. CONCLUSION. These data corroborate that the hypertension diagnosis should not be based in an single blood pressure determination and suggest that the recommendation to diagnose severe hypertension based on high values in the first two read-ings could misclassify some patients.