International collaborative study on juvenile hypertension. 2. First follow-up report. International Collaborative Group.

From 17 634 children born in 1964 and screened in 1977 two sample groups were selected: 10% of children from the upper 5% of the systolic and diastolic blood pressure distribution curves (95th percentile and above) were taken to form an "upper" group, and 10% from the remainder as a "lower" group. These children were re-examined in 1978. There was an 89% response rate (3640 children), with no difference in this rate between sexes or between the two groups. Data from the parents' responses to a questionnaire on themselves and the children were compared for differences between the two groups.The parents' ages, smoking habits and marital status, and the children's order of birth, number of siblings, and proportion of twins did not differ significantly between the upper and lower groups.The prevalence of hypertension and diabetes among the children, and the prevalence of hypertension, stroke and diabetes in the medical history of the parents were significantly higher in the upper than in the lower group. Signs of left ventricular hypertrophy and symptoms of a hyperkinetic heart syndrome (based on heart rate, innocent systolic murmurs, the magnitude of R and S waves on the ECG, and mean values of cardiothoracic and heart volume indices) occurred more frequently in the upper than in the lower group.Children in the upper group were sexually more developed, taller, more obese (higher Quetelet's index and skinfold thickness), and less active physically.Average values of blood sugar and serum uric acid were also higher in the upper than in the lower group. No significant difference was found between the two groups in the proportion of smokers among the children or in mean cholesterol values.These differences between the upper and lower groups were strengthened by the comparison of children who showed repeatedly a low arterial pressure below the 30th percentile of the systolic and diastolic blood pressure distribution curves.