Body mass index trend and its association with blood pressure distribution in children.

The aim of the study was to examine the association of a trend in body mass index (BMI) status with current blood pressure in a cohort of school children from South India. A population of 25,228 children was selected using stratified random sampling method. Height and weight were measured in 2003-2004. Height, weight and blood pressure were measured in 2005-2006. A total of 12,129 children aged 5-16 years having paired data were analysed. Blood pressure and BMI values were converted to Z scores using International paediatric reference values. An increase in Z BMI meant that the child is moving to a higher BMI level with respect to his or her age and sex. In the cohort, 62.4% children had a higher Z BMI at follow-up than at baseline. Children with higher Z BMI at follow-up were labelled as positive BMI status group (PBSG) and the remaining as negative BMI status group (NBSG). The positive trend in BMI was more in rural areas, government schools and girls. In all subgroups, PBSG showed significantly higher systolic blood pressures (SBPs) than NBSG. PBSG showed significantly higher diastolic blood pressures (DBPs) in urban area, government schools and girls when compared with NBSG. Prevalence of first instance systolic hypertension was more in PBSG in all the subgroups except in rural children. Prevalence of diastolic hypertension was significantly higher in PBSG in urban subgroup only. BMI status trends are associated with blood pressure distribution in children.