Abstract
OBJECTIVE: To examine secular trends in blood pressure over a 10 year period between two representative cohorts of adolescents from Northern Ireland. DESIGN: Repeat cross sectional study. SETTING: Randomly selected post-primary schools from Northern Ireland. PARTICIPANTS: 1015 adolescents studied between 1989 and 1990, and 2017 adolescents studied between 1999 and 2001. Participants were aged 12 or 15 years. MAIN OUTCOME MEASURES: Systolic and diastolic blood pressure measured by one observer in each study. RESULTS: The four groups for sex and age showed decreases in both systolic blood pressure (mean decrease 7.7 mm Hg to 10.0 mm Hg) and diastolic blood pressure (8.8 mm Hg to 11.0 mm Hg). These decreases were not accounted for by adjustment for potential confounders including age, height, body mass index, smoking, physical activity, aerobic fitness, and stratification of school by education board area and type. The findings were not altered by additional adjustment for social class, pubertal status, birth weight, and infant feeding. No evidence was found of systematic variation between observers. CONCLUSIONS: Substantial decreases in systolic and diastolic blood pressure over the past decade in adolescents from Northern Ireland are likely to have important benefits to public health and may help offset the increasing risk of cardiovascular disease due to increases in obesity.