Twelve-year tracking of blood pressure in Korean school children: the Kangwha Study

Longitudinal data from different populations have shown different degrees o f tracking of blood pressure (BP). To examine BP tracking in Korean school children, 219 of 430 children (100 males, 119 females) who were 6 years old in 1986 in Kangwha County, Korea have been examined annually up to 1997 in the Kangwha Study. BP was measured twice with standard mercury sphygmomano meters and the average of the two measurements was used for the level of BP . Diastolic BP were measured at the fourth Korotkoff sound. Tracking was ex amined using a time-lag correlation analysis and McMahan's tracking index t au, which indicates the proportion of variation attributable to tracking ap art from the natural growth component. As well the jackknife method was use d to obtain the confidence interval of tau. Correlation coefficients betwee n systolic BP from age 6 to 17 ranged from 0.39-0.54 for males and 0.44-0.5 7 for females. Taus for systolic BP were 0.875 (95% CI: 0.803-0.947) and 0. 900 (95% CI: 0.809-0.991) in males and females, respectively. Correlation c oefficients between diastolic BP from age 6 to 17 ranged from 0.28-0.47 for males and 0.14-0.47 for females. Taus for diastolic BP were 0.983 (95% CI: 0.897-1.000) and 0.800 (95% CI: 0.717-0.883) in males and females, respect ively. These findings showed strong evidence for BP tracking in Korean scho ol children from childhood to late adolescence.