Trends in blood pressure in 9-11 year-old children in the UK 1980-2008: the impact of obesity

Li, Leah

INTRODUCTION: High blood pressure (BP) is a major public health issue, both in the UK and worldwide. Although adult BP levels are declining in many populations including the UK, there is little published information on BP trends in children, a particular concern in the context of the rising levels of childhood adiposity. Our aims are to determine whether BP in children has changed over time and whether the change reflected trends in adiposity.

METHODS: We collated data on over 25,000 children aged between 9-11 years (mean 10.3 years) from seven population-based studies conducted in the UK between 1980 and 2008. Children of white European origin between 9 and 11 years of age were included. Adjustments were made to account for differences in mean ages, BP devices and cuff sizes used in different studies.

RESULTS: Mean systolic blood pressure (SBP) increased over time both in boys and girls: annual increases were 0.45mmHg (95% CI: 0.43, 0.48) for boys and 0.51mmHg (0.49, 0.53) for girls. Mean BMI increased by 0.064 kg/m²(0.060, 0.068) per year for boys and 0.070kg/m²(0.065, 0.074) for girls; the prevalence of overweight/obesity increased from 5.7% to 21.1% and from 9.7% to 24.1% respectively. The SBP trends occurred both in children with low and high BMI, but were more marked in low BMI group; BMI explained only 15.3% (15.1%, 15.6%) of increases in SBP for boys and 14.9% (14.6%, 15.1%) for girls. The BMI/SBP association appeared to become weaker over time (p<0.001 for negative interaction from 1984). There was only a modest annual increase in diastolic blood pressure (<0.1mmHg).

CONCLUSIONS: SBP levels have increased with time, but the increase is not explained by increased BMI. Further research is needed to identify the factors responsible.