Small or medium cuff

Children’s height and weight were measured at schools at age 6 and 9 years, with blood pressure also measured at 9 years. Height was measured to the nearest 0.1cm using a SECA Leicester stadiometer, and weight was measured to the nearest 0.1kg using a SECA 899 digital scale (HAB International, Northampton). BMI was derived as weight (kg)/ height (m)² and converted to an age- and gender-specific standard deviation score based on UK 1990 growth centiles [37 (link)]. This was then categorised as normal weight (<85th percentile) or overweight/obese (≥85th percentile). Blood pressure was measured using an Omron 907 Professional Blood Pressure Monitor [38 ] with a small or medium cuff (OMRON Corporation, Kyoto, Japan), three times, one-minute apart, in the left arm with the child seated and after a three-minute rest period. The average of all three measurements was used in analysis, or the average of two measurements for the 7% of children who did not have a third measure. Systolic and diastolic hypertension were defined as the systolic or diastolic blood pressure, respectively, that was ≥95^th percentile using US children’s blood pressure references that have been standardized for age, gender, and height [39 (link)]. US reference charts were used because of the lack of such population references for UK children.

Blood pressure was measured in the child’s school by trained fieldworkers using an Omron 907 Professional Blood Pressure Monitor [50 ] with a small or medium cuff (OMRON Corporation, Kyoto, Japan). After three minutes of rest, measurements were taken, using the appropriate cuff size, three times, one-minute apart, in the left arm while the child was seated. Of the 1296 children who participated at age 11, we have included 1283 (99%) children who provided at least two blood pressure measurements at age 11, in the current study. The mean of all available blood pressure measurements was used in the analyses. In our main analyses we examined associations with difference in mean blood pressure as a continuous variable. We also examined associations with high systolic and diastolic blood pressure, defined as the systolic or diastolic blood pressure that was ≥95^th percentile using US children’s age, sex and height standardized blood pressure references [51 (link)]. US reference charts were used because of the lack of such population references for UK children.