[Blood pressure study in school-children of Zurich. I. Results in the age group 7 to 12 years].

A longitudinal blood pressure study of 1575 children aged 7-11 years was started in 1977. 308 12-year-old children were rescreened one year later. The blood pressure was recorded at school in the sitting position using random-zero-sphygmomanometers and the largest cuff to fit the upper arm easily (10 cm and 12 cm wide). Systolic and diastolic II (disappearance of sounds) pressures were measured, and the mean of two readings (1st/2nd, or 3rd/4th if indicated) was used. The blood pressure values were remarkably low, with mean systolic pressures of 98 mm Hg or less and diastolic pressures of 55 mm Hg or less. The highest readings observed were 140 mm Hg systolic and 95 mm Hg diastolic in two 11-year-old children. The systolic blood pressure correlated best with weight (r = 0.38 in boys and 0.45 in girls), and, in decreasing order, with height (r = 0.32/0.40), age (r = 0.28/0.32) and triceps skinfold thickness (r = 0.24/0.26). Correlation with pulse rate was poor (r = 0.09/0.06). However, a multiple regression analysis showed that weight and pulse rate are the only variables which contribute significantly to explaining the variance of systolic blood pressure (17% in boys and 24% in girls). At constant height levels there was no correlation between systolic blood pressure and age, but the correlation with weight remained good and with skinfold thickness fair. Thus, the blood pressure in children aged 7-12 years correlates better with indices of body size (weight and Quetelet index) than with fatness, except in clearly obese children. Repeated blood pressure recordings correlated significantly with values obtained one year earlier: in boys, r = 0.49 for systolic and 0.34 for diastolic pressures, in girls, r = 0.58 (systolic) and 0.41 (diastolic). Repeatedly elevated systolic blood pressures, i.e. values within the upper decile, were observed four times more frequently than could have been expected by chance alone (in 14 of 36 children = 39%). Positive tracking correlations of blood pressure are therefore demonstrable in childhood.