The relationship between obesity and blood pressure differs by ethnicity in Sydney school children

The objective of this study was to investigate the relationship between obesity and high systolic blood pressure (SBP) in Southeast Asian (SEAsian) and Australian children living in Australia.

SBP, country of birth, and obesity indices (body mass index (BMI), waist circumference (WC), and percent body fat (%TBF)) were recorded in 1,232 9-year-old children from Sydney schools and remeasured 3 years later (n = 628). The relationship between SBP and obesity (both at baseline and longitudinally) was investigated by regression analyses.

Children of SEAsian origin had a significantly higher risk of high SBP with increases in obesity indices compared to those of Australian origin. At 9 years old, SBP increased 1.51 mm Hg for each of BMI increase for SEAsian children compared to 1.05 mm Hg for Australian children (P(interaction) = 0.03). These same significant analysis of variance (ANOVA) interactions were seen with WC (P(interaction) = 0.02) and %TBF (P(interaction) = 0.04) as predictors of SBP. These differences by ethnic background were also reflected in the 3-year longitudinal analysis where SEAsian children showed higher risk of increasing SBP with BMI increase (SBP increased 1.70 mm Hg for each unit of BMI increase for SEAsian children compared to 0.80 mm Hg for Australian children (P(interaction) = 0.02)) or with WC increase (P(interaction) = 0.01), whereas these increases were small and nonsignificant in Australian children.

These findings suggest that SEAsian children living in Australia are at higher risk of increasing SBP than their Australian counterparts when they become overweight or obese.