Physiologic increase and tracking of blood pressure in schoolchildren.

4343 blood pressure (BP) recordings were obtained in 1575 schoolchildren during 5 years. Systolic BP rose proportionally to upper arm muscle area (MA) in both sexes. In contrast, upper arm fat area (FA) was considerably lower in boys than in girls, and the rise of systolic BP in boys during puberty was not accompanied by any increase of FA. At repeat examination of 900 children after 1 to 5 years, between 35% and 53% of those with initial systolic BP in the highest quintile had again values in the same quintile, thus twice as often as expected. Tracking in the highest decile was even stronger: 37% of 82 children had again systolic BP in the highest decile at 2 years, and 29% at 4 to 5 years. We conclude that the physiologic increase of systolic BP is primarily determined by rising muscle mass, and tracking still remains detectable in children after 4 to 5 years and is strongest in those with highest values.